US Army Mechanic Course - Maintenance of Wheeled Vehicle M998 (HMMWV) IN0511

8/10/2019 US Army Mechanic Course - Maintenance of Wheeled Vehicle M998 (HMMWV) IN0511

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PREFACE

The Army Institute for Professional Development (AIPD) administers

the consolidated Army Correspondence Course Program (ACCP), which provides

highquality, economical training to its users. The AIPD is accredited by

the Accrediting Commission of the Distance Education and Training Council

(DETC), the nationally recognized accrediting agency for correspondence

institutions.

Accreditation is a process that gives public recognition to

educational institutions which meet published standards of quality. The

DETC has developed a thorough and careful evaluation system to assure that

institutions meet standards of academic and administrative excellence

before it awards accreditation.

The many TRADOC service schools and DOD agencies that produce the

ACCP materials administered by the AIPD develop them to the DETC standards.

The AIPD is also a charter member of the Interservice Correspondence

Exchange (ICE). The ICE brings together representatives from the Army,

Navy, Air Force, Marine Corps, and Coast Guard to meet and share ideas on

improving distance education.

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MAINTENANCE OF WHEELED VEHICLE M998 (HMMWV)

Subcourse Number IN 0511

EDITION B

United States Army Infantry School

Fort Benning, Georgia 31905-5593

6 Credit Hours

Edition Date: June 1995

SUBCOURSE OVERVIEW

This subcourse is designed to teach you how to effectively maintain various

systems on the M998 Wheeled Vehicle (HMMWV)

including the air cleaner system, brake system, cooling system, battery

system, engine and fuel system, steering system, and transmission system.

Additionally, this subcourse will teach you how to start the HMMWV using

auxiliary power, how to operate and maintain the Nuclear, Biological, or

Chemical (NBC) system, and how to conduct towing operations.

There are no prerequisites for this subcourse.

This subcourse reflects the doctrine which was current at the time it was

prepared. In your own work situation, always refer to the latest

publications.

The words "he," "him," "his," and "men," when used in this publication,

represent both the masculine and feminine genders unless otherwise stated.

TERMINAL LEARNING OBJECTIVE

ACTION: You will identify procedures used to maintain the various

systems of the HMMWV. You will also identify procedures

used to start the HMMWV using auxiliary power, to operate

and maintain the NBC system, and to conduct towing

operations.

CONDITION: You will use the information contained in this subcourse.

STANDARD: To demonstrate competency of this subcourse, you must

achieve a minimum of 70% or higher on the subcourse

examination.

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TABLE OF CONTENTS

SECTION PAGE

Subcourse Overview .. . . . . . . . . . . . . . . . . . . . i

Administrative Instruction . . . . . . . . . . . . . . . . iv

Grading and Certification Instructions . . . . . . . . . . iv

Lesson 1: Maintain the Air Cleaner, Brake,

Cooling, and Battery Systems . . . . . . . . . . . . . 1

Part A: Maintain the Air Cleaner System . . . . . . . 2

Part B: Maintain the Brake System . . . . . . . . . . 10

Part C: Maintain the Cooling System . . . . . . . . . 13

Part D: Maintain the Battery System . . . . . . . . . 18

Practice Exercise . . . . . . . . . . . . . . . . . . 22

Answer Key and Feedback . . . . . . . . . . . . . . 24

Lesson 2: Maintain the Engine, Fuel, Steering and

Transmission System . . . . . . . . . . . . . . . . . . 27

Part A: Maintain the Engine . . . . . . . . . . . . . . 27

Part B: Maintain the Fuel System . . . . . . . . . . . 43

Part C: Maintain the Transmission System . . . . . . . 45

Part D: Maintain the Steering System . . . . . . . . . 49

Practice Exercise . . . . . . . . . . . . . . . . . . . 55

Answer Key and Feedback . . . . . . . . . . . . . . . . 58

Lesson 3: Start the M998 Wheeled Vehicle using

Auxiliary Power, Operate and Maintain the NBC System, and

Conduct Towing Operations. . . . . . . . . . . . . . . . .61

Part A: Start an M998 Wheeled Vehicle

using Auxiliary Power . . . . . . . . . . . . . . . . . .62

Part B: Operate and Maintain the NBC

System on an M996, M997, Series Vehicle . . . . . . . . 62

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Part C: Towing an M998 Series Wheeled

Vehicle . . .. . . . . . . . . . . . . . . . . 70

Practice Exercise . . . . . . . . . . . . . . . . 78

Answer Key and Feedback . . . . . . . . . . . . . 81

Examination . . . . . . . . . . . . . . . . . . . . . . . E-1

Student Inquiry Form

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ADMINISTRATIVE INSTRUCTIONS

1. Number of lessons in this subcourse: Three.

2. Materials needed in addition to this booklet are a #2 lead pencil, an

ACCP examination response sheet, and a preaddressed envelope you receivedwith the subcourse.

3. Supervisory requirements: None.

GRADING AND CERTIFICATION INSTRUCTIONS

Examination: This subcourse contains a multiple-choice examination

covering the material contained in the three lessons. After studying the

lessons and working through the practice exercises, complete the

examination. Mark your answers in the subcourse booklet. Then transfer

them to the ACCP examination response sheet. Completely black out thelettered oval which corresponds to your selection (A, B, C, or D). Use a

#2 lead pencil to mark your responses. When you have completed the

examination response sheet, mail it in the preaddressed envelope you

received with the subcourse. You will receive an examination score in the

mail. A score of 70% or higher is passing. Six credit hours will be

awarded for successful completion of this examination.

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LESSON 1

MAINTAIN THE AIR CLEANER, BRAKE, COOLING,

AND BATTERY SYSTEMS

MOS Manual Task: 551-721-1342

551-721-1343

551-721-1344551-721-1349

OVERVIEW

LESSON DESCRIPTION:

In this lesson you will learn how to maintain the air cleaner, brake,

cooling, and battery systems on the M998 Wheeled Vehicle.

TERMINAL LEARNING OBJECTIVE:

ACTION: Identify the procedures to perform maintenance on the

air cleaner, brake, cooling, and battery systems on the

M998 Wheeled Vehicle (HMMWV).

CONDITION: You will be given information contained in this lesson.

STANDARD: Performing maintenance checks on the M998 Wheeled

Vehicle.

REFERENCE: The material contained in this lesson was derived from

the following publication:

TM 9-2320-280-10

INTRODUCTION

You must correctly perform maintenance procedures in order to prolong

the operating life of the M998 Wheeled Vehicle (HMMMV) and to ensure

your unit is totally reliable when employed in tactical situations.

Upon completion of this lesson you will be able to identify procedures

used when performing maintenance on the air cleaner, brake, cooling,

and battery systems on the HMMMV.

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PART A - MAINTAIN THE AIR CLEANER SYSTEM

1. Function of the Air Cleaner Assembly.

The air cleaner assembly located at the right rear section of the

engine (Figure 1-1), filters dirt and dust from induction air before

it enters the combustion chamber of the engine. This assemblycontains a single filter element that you can remove for servicing or

replacement when it no longer functions properly.

Figure 1-1. Air Cleaner Assembly.

2. Function of the Air Cleaner Dump Valve.

The air cleaner dump valve, located at the bottom of the air cleaner

assembly, allows you to clear the air filter assembly of any buildup

of dirt, water, mud, or anything else that may have entered the air

intake system. On vehicles not equipped with the deep water fording

kit, simply squeeze the dump valve to release any debris from the air

filter assembly. On units with a deep water fording kit installed,

you remove the dump valve, clean it, and replace it. For example, if

your unit conducted an operation that required you to operate your

HMMWV in mud and water you would carry out air cleaner dump valve

servicing steps (listed below) at the completion of the exercise. Any

concentration of dirt, water, or mud in the air cleaner assembly that

cannot be cleared through the dump valve must be removed by servicing

the air cleaner assembly itself.

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3. Servicing the Air Cleaner Assembly.

Use the following procedures to service the air cleaner assembly on

your HMMWV.

a. Raise the Vehicle Hood. Before performing any type of service

on the engine of your HMMWV, you must raise the hood. Although thisseems like a simple task, you must still exercise caution. Here's

why. The hood assembly is relatively heavy. When you lift it you may

possibly injure yourself if you don't use proper lifting techniques.

Additionally, because the hood assembly is heavy, it is likely to flex

as you attempt to open it. Interference between the right side of the

hood assembly and the body of the HMMWV could be caused. To eliminate

this interference, you simply push the hood assembly sideways, away

from yourself, before you lift. Use the following procedures when you

to raise the hood on your HMMWV.

Apply the vehicle parking brake.

Release the left and right hood latches (Figure 1-2).

Figure 1-2. Vehicle Hood Components.

While facing the driver's side of the hood, put one of your

hands at the rear of the hood while placing your other hand at

the rear of the wheel well.

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Open the hood assembly by lifting it in an upward direction.

Make sure you secure the hood rod in the hood support bracket

(Figure 1-2). The prop should automatically engage the

support bracket once you raise the hood, however, do not fully

release the hood until you are sure the prop is engaged.

Now that the hood is fully raised, you are ready to service yourengine.

b. Air Cleaner Dump Valve Servicing. You service the air

cleaner dump valve, shown in Figure 1-3. After all operations where

your HMMWV is exposed to water, mud, sand, or any other type of

substance that could be taken into the air cleaner assembly. Use the

following procedures to service the air cleaner assembly dump valve on

your HMMWV.

Figure 1-3. Air Cleaner Dump Valve Servicing.

(1) Dump Valve Servicing (Without Deep Water Fording Kit).

Remove water and mud from the air cleaner assembly by squeezing the

dump valve to release any debris.

(2) Dump Valve Servicing (With Deep Water Fording Kit). If

your HMMWV is equipped with a deep water fording kit you remove the

dump valve, clean, and reinstall it. Use the following procedures to

accomplish this task.

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Loosen the clamp around the dump valve.

Remove the cap that covers the dump valve opening.

Clean the dump valve cap and reinstall it.

Tighten the clamp around the dump valve.

NOTE: Once you remove the dump valve cap, any debris

trapped in the air cleaner assembly should come

out of the hole once covered by the cap.

c. Lower the Vehicle Hood. Just as there were certain

precautions when raising the vehicle hood, there are also precautions

you take when lowering the hood. For instance, when you release the

hood prop rod, be careful not to pull the rod from the hook side

(Figure 1-2). The hood could suddenly drop, causing injury to your

fingers. Use the following procedures to safely lower the vehicle

hood once you have completed maintenance on the vehicle engine.

With one hand, support and slightly raise the vehicle hood.

Using your other hand, grasp the prop rod above the retaining

ring (Figure 1-2).

Pull the rod out and release the hood prop rod making sure

that the prop rod hook is clear of the support bracket.

Slowly lower the vehicle hood.

Secure the left and right hood latches (Figure 1-2).

4. Weekly Check of the Air Intake Portion of the Air Cleaner

Assembly.

a. You perform Preventive Maintenance Checks and Services (PMCS)

on the air intake (refer to Figure 1-4.) on a periodic basis when

operating the vehicle under normal conditions. You must perform PMCS

more often when you operate your vehicle under unusual conditions or

when malfunctions occur.

b. You inspect the air intake system weekly for evidence of

damage to the weathercap, air cleaner assembly, and air intake hose

and for security of mounting. It is important that you perform these

checks as prescribed in order to find and correct discrepancies, which

would permit entry of unfiltered air to the engine. You

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inspect the weathercap for damage. Replace if damaged.

inspect the air cleaner assembly and air intake hose for

secure mounting and evidence of damage.

inspect the air cleaner mounting hardware for damage or

looseness.

Figure 1-4. Air Intake Servicing.

5. Air Cleaner Servicing (Emergency Procedures).

At times you may have to service the air cleaner using emergency

procedures. This occurs when the yellow indicator of the air

restriction gage (Figure 1-5) is in the red zone, or whenever the

vehicle has been operated in an environment in which exposure to

Nuclear, Biological, or Chemical (NBC) agents has occurred.

a. Filter Element Removal.

(1) Raise Vehicle Hood. After the hood is fully raised,

you are ready to service the air cleaner assembly.

(2) Filter Element Removal.

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Figure 1-5. Air Filter Restriction Gauge.

First, you loosen the bolt on the filter canister clamp and

remove the cover from the air cleaner assembly.(Figure 1-6)

Figure 1-6. Filter Element Components.

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Then, remove the nut and washer from the filter-mounting stud,

and remove the filter element from the air cleaner assembly.

Now, reinstall the air cleaner assembly cover and clamp to

prevent dirt and dust from entering the air induction system

while you are cleaning the filter element.

Do not operate the engine without the air filter installed.

Damage to the engine will result.

If air filters have been exposed to NBC contaminants, you must

handle them with extreme precaution and they must be disposed

of by trained personnel. Unprotected personnel may experience

injury or death if residual toxic agents or radioactive

material are present. When servicing, you must wear

protective overgarments, mask, hood, and chemical protective

gloves and boots. Place contaminated air filters into double

lined plastic bags and move immediately to a temporary

segregation area away from the work site. Final disposal of

NBC contaminated air filters will be in accordance with local

SOP.

b. Filter Element Cleaning. Hold the filter element with the open

end facing the ground. Gently tap the filter element outer

circumference with your hand to dislodge trapped dirt (figure 1-7).

Do not strike the ends of the filter element on the ground or other

hard surface as damage to the filter element may occur.

Figure 1-7. Air Filter Element Cleaning.

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c. Filter Element Installation. Perform the following steps to

reinstall the filter element after cleaning.

Loosen the clamp and remove the cover from the air cleaner

assembly.

Position the filter element into the air cleaner assembly andsecure the filter element on the air cleaner center stud with

the nut and washer.

Install the cover onto the air cleaner assembly and secure in

place with the clamp assembly. Take care to position the

clamp so that the bolt is on the bottom of the air filter

assembly (as shown in Figure 1-8). This will assure proper

clearance when the hood of the vehicle is closed.

Lower and secure the vehicle hood.

Figure 1-8. Filter Element Components.

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PART B - MAINTAIN THE BRAKE SYSTEM

1. Brake Master Cylinder.

When the brake pedal on the M998 series Wheeled Vehicle is depressed,

the brake master cylinder piston is moved. This movement exerts

hydraulic fluid pressure proportioned to fulfill the requirement ofthe hydraulic brake system.

a. Brake Fluid Servicing.

(1) Raise Vehicle Hood. After the hood is fully raised, you are

ready to service the brake master cylinder assembly. Locate the brake

master cylinder on the engine firewall to the left and to the rear of

the engine (Figure 1-9).

(2) Brake Fluid Servicing. The master cylinder reservoir holds

the brake fluid, which the system uses to operate the brake system.

You must service the brake fluid reservoir to the proper level for thebrake system to operate properly.

Figure 1-9. Brake Fluid Servicing.

First, you thoroughly clean the exterior of the master

cylinder and master cylinder cover before removing the cover.

Dirt, water, or grease will contaminate brake fluid in the

cylinder and cause brake system damage.

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Then, remove the cover from the master cylinder by moving the

bail wire. Use thumb pressure only, first on the front part

of the bail wire and second at the back part of the bail wire.

Now, check the fluid level in both reservoirs. Fluid level

should be approximately 1/8 inch from the top edge of thereservoir chambers. If fluid level is low, add brake fluid to

replenish the reservoirs to the proper level.

Inspect the master cylinder rubber diaphragm to ensure that

the diaphragm is properly seated in the cover and that no

distortion exists. Fluid spillage will occur if the cover is

reinstalled with a distorted diaphragm. Ensure that no

foreign material is on the diaphragm.

Finally, install the master cylinder cover taking care to

ensure that the bail wire is firmly seated in the indentations

on the cylinder cover. Wipe away any fluid, which may have

spilled, during the servicing.

(3) Now that you have finished servicing the brake fluid,

lower and secure the vehicle hood.

2. Parking Brake Service Checks on a Weekly Basis and During

Operation.

a. Parking Brake Service Checks During Operation. With the

vehicle stopped, the engine running at idle, and the transmission

drive selector in "D", set the parking brake and release the brake

pedal. If the vehicle moves forward with the parking brake set, theparking brake system requires adjustment and the vehicle is not ready

for operation.

b. Parking Brake Service Checks on a Weekly Basis. If the

vehicle is equipped with a left and right parking brake/service brake

assembly, it is necessary to inspect the parking brake assembly for

obstruction or broken hardware. The vehicle is not serviceable if the

actuator lever or spring is missing or broken. (Figure 1-10.)

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Figure 1-10. Parking Brake Service Checks on a Weekly Basis.

3. Troubleshooting the Parking Brake System.

a. Brake Warning Lamp Assembly On. If the brake warning lamp is

illuminated, check to see if the parking brake is partially engaged.

If the parking brake lever is not engaged, check for low fluid level

in the brake master cylinder. If both the fluid level and the parking

brake lever are normal, refer the discrepancy to Organizational

Maintenance for troubleshooting and repair.

b. Parking Brake Fails To Hold Vehicle. If the parking brakedoes not hold the vehicle stationary when the engine is idling and the

parking brake is set, you may need to clean or adjust the parking

brake. You proceed as follows:

Chock the wheels and release the parking brake handle.

Turn the adjusting knob at the end of the parking brake handle

clockwise as far as it will go. This adjustment takes up any

slack in the parking brake cable.

Set the parking brake handle to the brakes ON position.

If you cannot set the parking brake handle to it's brakes ON

position, turn the brake handle-adjusting knob

counterclockwise only far enough to permit the parking brake

to be applied with normal pressure.

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To test the parking brake: you remove the chocks from the

vehicle wheels.

you depress the service brake pedal and start the

engine.

With the engine idling, place the transfer case shift

lever into the "HIGH" (H) position and the transmission

shift lever in the "DRIVE" (D) position.

You slowly release the service brake pedal. The parking

brake should hold the vehicle stationary.

After operating the vehicle in mud or sand, you must clean

parking brake components of foreign matter using low-pressure

water. Ensure that the parking brake pad, pad-rotor contact

area, guide pins, and pushpins are thoroughly cleaned of mud,

sand, and debris (Figure 1-11).

Figure 1-11. Parking Brake Adjustment and Cleaning.

PART C - MAINTAIN THE COOLING SYSTEM

The M998 series vehicle engine is cooled by a 26-quart liquid coolant

cooling system, which employs a downflow type radiator. A 10-blade

19-inch fan pulls outside air through the radiator core. The

internally mounted cooling system thermostat regulates coolant flow

through the radiator to maintain a normal operating coolant

temperature between 190-230F. The cooling system operates at a

pressure of 15 psi to help prevent overheating and boilover.

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2. Starting the Engine.

The M998 series vehicle does not have a "PARK" position on its

automatic transmission. Whenever the vehicle is parked or the

transmission is in neutral, the parking brake MUST BE APPLIED. Damage

to equipment or injury to personnel may occur if you do not set the

parking brake prior to starting the engine.

Perform the following procedures when starting the engine. Use Figure

1-13 to follow these procedures.

Figure 1-13. M998 Wheeled Vehicle Controls and Indicators.

a. Make sure that the parking brake is set. If it is not set, apply

the parking brake.

b. Adjust the driver's seat for a comfortable position in which all

controls may be reached easily. Ensure that the seat mount pins are

positively positioned in the desired slots to prevent seat movement

while operating the vehicle.

c. Adjust the left and right rear view mirrors. Make sure that both

mirrors provide you a clear view of objects to the rear and sides of

the vehicle.

d. Pull the seat belt across your body and fasten the strap to the

belt buckle. Pull the adjusting strap to remove slack

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e. Place the transmission shift lever, shown as (8) in Figure 1-13,

into the neutral (N) position and the transfer case shift lever (7) in

the desired position (normally high range).

f. Place the rotary switch (1) to "RUN" and wait until the WAIT-TO-

START lamp (2) goes out. The WAIT-TO-START lamp indicates when the

engine glow plugs are sufficiently heated to effect a positive enginestart.

CAUTION: It is important that you do not leave the rotary

switch in the RUN position after the WAIT-TO-

START goes out. Damage to the glow plugs will

result.

g. When the "WAIT-TO-START" lamp goes out, turn the rotary switch to

the START position. Release the switch when the engine starts. The

rotary switch will automatically return to the RUN position.

CAUTION: If the ambient temperature is above 0F. (-17

C.), do not operate the starter for more than 20

seconds continuously. Failure to observe this

precaution will result in damage to the starter.

Wait 10 to 15 seconds between periods of starter

operation.

h. Check your engine instruments while allowing the engine to warmup (approximately one minute). Engine instruments should read as

follows:

The oil pressure gage (4) should register approximately 6 psi

(41kPa) with the engine at idle speed.

The voltmeter (6) registers in the Green area.

The fuel gauge (9) indicates the fuel level in the fuel tank.

The air restriction gage (3) should not register within the

red zone.

i. Stop the engine immediately if any of the following conditions

occur:

There is excessive engine vibration.

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The oil pressure does not register, or suddenly drops below 6

psi with the engine at idle. from the seat belt. The seat

belt must fit you snugly across the hips.

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The air restriction gage is within the red zone.

j. If engine overheating occurs, perform the following steps:

Park the vehicle and allow the engine to idle.

Observe the coolant temperature gage for steady cooling.

If the engine coolant temperature continues to increase or

does not decrease as indicated by the coolant temperature gage

(8), stop the engine and perform fault isolation to determine

the cause for overheating. In any case, do not permit the

coolant temperature to exceed 230F. (110C.) or damage to the

engine will result.

3. Stopping the Engine.

The M998 series vehicle does not have a "PARK" position on its

automatic transmission. Whenever the vehicle is parked or the

transmission is in "NEUTRAL", the parking brake MUST BE APPLIED.

Perform the following steps when you stop the engine:

a. Apply the parking brake and place the transmission shift lever

in NEUTRAL.

b. Place the rotary switch in the "ENG STOP" position.

c. Lock the steering with the security cable and chock the

vehicle wheels if the tactical situation permit.

4. Servicing the Coolant Surge Tank

Under ideal conditions, you service the engine coolant surge tank

prior to operation and while the engine is cool. Under some

circumstances, however, it will be necessary to service the coolant

surge tank during or after engine operation. You should take extreme

care when servicing the coolant surge tank when the coolant

temperature gage reads above 165F. (74C.). Do not add coolant to

the surge tank when the engine is hot unless the engine is running.

Add coolant slowly. Steam or hot coolant under pressure will cause

injury. After fully raising the hood you are ready to service the

coolant surge tank.

Your first step is to visually check the coolant level in the

surge tank. The coolant should be level with the "COLD FILL

LINE" if the engine has not been operated, or slightly above

the "COLD FILL LINE". If the coolant level is low, proceed to

service the surge tank with approved coolant.

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Next, place a thick cloth over the coolant surge tank filler

cap and turn the cap counterclockwise to the first stop to

allow cooling system pressure to escape.

After the cooling system pressure has been vented, remove the

cap from the surge tank and add approved coolant until the

level of the coolant is even with the "COLD FILL LINE".

With the coolant surge tank cap removed, start the engine and

run for one minute.

Then, stop the engine and recheck the coolant level. If the

coolant level is low, add coolant until the surge tank coolant

level is at the "COLD FILL LINE".

Repeat the above two steps until the coolant level remains at

the "COLD FILL LINE".

Install the coolant surge tank cap taking care to ensure that

the cap is properly secured.

(3) Lower and secure vehicle hood.

Now that you have completed servicing the coolant surge tank,

lower and secure the hood of your vehicle.

PART D - MAINTAIN THE BATTERY SYSTEM

1. Batteries and Battery Box.

There are two 12-volt lead acid batteries mounted in the battery box

located under the companion seat (Figure 1-14). They provide 24 volt

electrical power to the vehicle electrical system. The two latches on

the front of the companion seat (Figure 1-14) release to permit

removal of companion seat for access to the batteries.

2. Slave Receptacle.

A slave receptacle is located on the outside front of the battery box

(Figure 1-15). The slave receptacle is the connecting point for the

slave cable for slave starting the vehicle.

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Figure 1-14. Batteries and Battery Box.

Figure 1-15. Slave Receptacle.

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3. Checking Batteries.

a. Do not perform battery checks or inspections while smoking or

when in the vicinity of open flames or sparks, especially if the

battery cell filler caps are removed. Batteries may explode

causing death or injury to personnel and damage to the vehicle.

b. Preventive Maintenance Checks and Services (PMCS) require that

you check the electrolyte level and battery material condition on a

weekly basis.

Remove the companion seat (Figure 1-16) and inspect the

batteries for security of mounting, damaged casings, and

corrosion or damage to battery posts.

Then, unscrew and remove the battery cell filler caps and

check the electrolyte level. Electrolyte should be level with

the ledge inside the cells. If the electrolyte level is low,

notify organizational maintenance.

Inspect the battery box for damage or corrosion. Clean any

debris from the battery box and drain holes.

Figure 1-16. Servicing Batteries.

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4. Servicing Batteries

To service the batteries, you again unhook the latches securing the

companion seat to the battery box and remove the companion seat to

gain access to the batteries.

a. Your first step is to check the electrolyte level.

Unscrew and remove all battery filler caps and check the

level of the electrolyte in each battery cell. If the

electrolyte is below the ledge in the battery filler

opening, notify organizational maintenance.

A battery that is continually in need of electrolyte may

indicate an improperly adjusted charging system. Notify

organizational maintenance that a problem of habitually low

electrolyte is noted.

Inspect the vented filler caps to ensure that vent openingsare clear and unobstructed. Clean the vents if they are

obstructed prior to reinstalling on the battery. Replace

any damaged filler caps you find during servicing.

Then, reinstall the battery filler caps. The caps should be

hand tightened only.

b. Inspect all battery compartment components including cerminal

clamps, battery cables, battery hold down, and shunt assembly for

corrosion, damage, or looseness. Notify organizational maintenance if

any of these problems exist.

c. Ensure that the battery cable clamps have a light coating of

GAA for corrosion protection.

d. Install the companion seat and secure the seat to the battery

box with latches.

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LESSON 1

Practice Exercise

The following items will test your knowledge of the material covered

in this lesson. There is only one correct answer for each item. When

you have completed the exercise, check your answers with the answer

key that follows. If you answer any item incorrectly, study again

that part of the lesson, which contains the portion, involved.

Situation: You are an M998 Wheeled Vehicle operator assigned to a

field unit. Your unit has just completed an operation that required

you to operate your vehicle in water and mud. During the operation

you noticed several faults with your vehicle that require immediate

attention along with regularly scheduled maintenance.

1. To ensure that the air cleaner assembly can filter dirt and dust,

you

A. jar mud and water from the air cleaner assembly with a rubber

mallet.B. squeeze the air cleaner dump valve to release mud or water.

C. remove the air cleaner dump valve to release mud or water.

D. do not worry about the air cleaner. The dump valve will

automatically release trapped mud or water.

2. While conducting the weekly check on the air intake portion of the

air cleaner you notice that the weather cap is damaged. To remedy

this problem, you

A. replace the damaged weather cap.

B. temporarily tape the damaged weather cap.C. remove the damaged weather cap.

D. move on to other vehicle maintenance.

3. The brake fluid level in the master cylinder is 1/2 inch from the

top of the reservoir. Based on this observation, you

A. continue on with other vehicle maintenance because the level

is O.K..

B. fill the reservoir to the top with brake fluid.

C. fill the reservoir to within 1/8 inch from the top with brake

fluid.

D. remove brake fluid from the reservoir because it is above the

allowed level.

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4. The parking brake on your vehicle will not hold with the

transmission in "D" and the engine at idle. In response to this

problem, you

A. park the vehicle on a flat surface.

B. check to see if the engine idle is too high.

C. pull on the parking brake lever again.D. adjust the parking brake to hold the vehicle.

5. You check the coolant level in the surge tank and see that it is

at the cold fill line. As the next step, you

A. continue on with other vehicle maintenance checks. The level

is O.K..

B. add coolant to the surge tank. The level is too low.

C. drain coolant from the surge tank. The level is too high.

D. add water to the surge tank. The level is too low.

6. Before adding coolant to the surge tank of a warm vehicle, youcheck to see if the coolant gage in the cab reads

A. 165F (74C).

B. 180F (88C).

C. 180F (82C) or more.

D. 190F (88C).

7. You discover that the battery box drain holes are blocked by

debris. To solve this problem, you

A. continue on with the inspection. Blocked holes will not

cause a problem.B. notify organizational maintenance to remove the debris.

C. seal the battery box with sealing compound.

D. clean the debris from the battery box drain holes.

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LESSON 1

PRACTICE EXERCISE

ANSWER KEY AND FEEDBACK

Item Correct Answer and Feedback

1. B. squeeze the air cleaner dump valve to release mud or

water.

On vehicles not equipped with the deep water fording kit, it

is not necessary to remove the air cleaner dump valve. All

that is required is to squeeze it to release any debris.

(Page 4, para 3.b (1)).

2. A. replace the damaged weather cap.

The damaged weathercap will allow unfiltered air to enter the

engine, therefore it must be replace.(Page 6, para 3.b).

3. C. fill the reservoir to within 1/8 inch of the top with

brake fluid.

The level of brake fluid in the reservoir must be within 1/8

inch of the top. Check the level in both reservoirs. (Page

11, para 1.a (2)).

4. D. adjust the parking brake to hold the vehicle.

If the parking brake does not hold the vehicle, it needs

adjustment. The parking brake must be adjusted before the

vehicle is ready and available for service. (Page 12, para2.a).

5. A. continue on with other vehicle maintenance checks. The

level is O.K

At the cold fill line the coolant in the surge tank is at the

proper level for safe operation of the vehicle. (Page 14,

para 1).

6. A. 165F (74C).

It is dangerous to attempt to service the coolant if the

temperature is above 165 C. Therefore, you must check the

gage in the cab to ensure that it is

safe. (Page 17, para 4).

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7. D. clean the debris from the battery box drain holes.

The drain holes should not be blocke D. Remove the debris

from the holes so they can drain properly. (Page 20, para

3.b).

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THIS PAGE IS INTENTIONALLY LEFT BLANK

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LESSON 2

MAINTAIN THE ENGINE, FUEL, TRANSMISSION, AND

STEERING SYSTEMS ON THE M998 WHEELED VEHICLE


551-721-1346551-721-1347

551-721-1348

OVERVIEW

LESSON DESCRIPTION:

In this lesson you will learn how to maintain the engine, fuel,

transmission, and steering systems on the M998 Wheeled Vehicle.


ACTION: Identify the procedures followed to perform maintenance onthe engine, fuel, transmission, and steering systems on the

M998 Wheeled Vehicle.


STANDARD: Performing maintenance checks on the M998 Wheeled Vehicle.

REFERENCE: The material contained in this lesson was derived from the

following publication:

TM 9-2320-280-10

INTRODUCTION

Maintenance procedures must be correctly performed in order to prolong the

operating life of the M998 Wheeled Vehicle and to ensure the unit is

totally reliable when employed in tactical situations. Upon completion of

this lesson you will be able to identify procedures used to perform

maintenance on the engine, fuel, transmission, and steering systems on the

M998 Wheeled Vehicle.

PART A - MAINTAIN THE ENGINE

The M998 series Wheeled Vehicle is powered by an eight cylinder, 6.2 liter,

naturally aspirated, liquid cooled diesel engine. The engine produces 150

brake horsepower at 3600 rpm. Normal engine operating speed is 1500-2300

rpm. At idle, the engine speed is 650 rpm (plus or minus 25 rpm). At idle

rpm, engine oil pressure should normally be 15 psi (103 kPa). At normal

operating speed, the oil pressure should be 40-50 psi (275-345 kPa).

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1. Engine Components.

a. Power Steering Fluid Reservoir Cap/Dipstick. The power steering

fluid reservoir cap/dipstick (Figure 2-1) is located on the left front of

the engine. You remove the cap/dipstick to fill and/or check the power

steering fluid level.

Figure 2-1. Power Steering Fluid Reservoir Cap/Dipstick.

b. Transmission Oil Dipstick. The transmission oil dipstick is

located on the right rear of the engine immediately adjacent to the coolant

surge tank (Figure 2-2). You remove it to fill and/or check the

transmission fluid level. The dipstick on vehicles equipped with deep

water fording kits are threaded and screwed into the transmission oil

dipstick tube to prevent water from entering the transmission fluid supply.

Vehicles without deep water fording kits do not have threaded dipsticks.

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Figure 2-2. Transmission Oil Dipstick On Vehicles With and

Without Deep Water Fording Kits.

c. Transmission Oil Dipstick Tube. The transmission oil dipstick tube

is located on the right rear of the engine (Figure 2-3) and is the fill

point for transmission fluid. The transmission oil dipstick serves as a

cap for the transmission oil dipstick tube.

Figure 2-3. Transmission Oil Dipstick Tube.

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d. Engine Oil Dipstick. The engine oil dipstick is located on the

left side of the engine behind the alternator (Figure 24). Design of the

dipstick on vehicles equipped with deep water fording kits prevents water

entry into the engine crankcase.

Figure 2-4. Engine Oil Dipstick On Vehicles With and Without

Deep Water Fording Kits.

e. Engine Oil Filler Cap. The engine oil filler cap is located on the

center front of the engine (Figure 2-5). You remove the cap from the oil

filler neck to add oil to the engine.

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Figure 2-5. Engine Oil filler Cap.

Figure 2-6. Radiator Draincock.

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f. Radiator Draincock. The radiator draincock is located beneath the

right front of the engine (Figure 2-6) on the lower radiator crossover

pipe. You turn the draincock counterclockwise to drain the coolant from

the radiator.

Figure 2-7. Coolant Surge Tank Cap.

g. Coolant Surge Tank Cap. The coolant surge tank cap is located on

the coolant surge tank (Figure 2-7) at the right rear of the engine. You

remove the cap from the surge tank to add coolant to the cooling system.

h. Fuel Filter. The engine fuel filter (Figure 2-8, item 1) is

located on the engine firewall at the left rear of engine. The purpose of

the fuel filter is to remove water and sediment from the fuel before it

reaches the engine.

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Figure 2-8. Engine Components.

i. Windshield Washer Reservoir Cap. The windshield washer

reservoir is located at the left rear of the engine (Figure 2-8, item 2).

The reservoir cap unsnaps to add windshield washer fluid to refill the

reservoir.

j. Fuel Filter Draincock. The fuel filter draincock (Figure 2-8, item

3) is located on the engine cowl below and in front of the windshield

washer reservoir. This draincock is the drain point for any water which

may collect in the fuel filter.

k. Master Cylinder Cover. The master cylinder cover (Figure 2-8, item

4) is located at the left rear of the engine. You remove the cover to fill

and/or check the master cylinder brake fluid level.

l. Air Cleaner Assembly. The air cleaner assembly is located at the

right rear of the engine compartment (Figure 2-9).

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Figure 2-9. Air Cleaner Assembly.

2. Cleaning Instructions.

Cleaning is an after operation service performed by the operator/crew to

keep the vehicle in a high state of readiness. Facilities and material

available to operators for vehicle cleaning can vary greatly in differing

operating conditions. However, vehicles must be maintained in as clean a

condition as available equipment, materials, and tactical operating

conditions permit. The following lists show you the procedures for

cleaning all aspects of the HMMWV. Note that you use drycleaning solvent,

water, and rags to remove oil and grease from the engine transmission. Youcan remove salt, mud, dust, or debris by using soapy water, a soft wire

brush, or damp and dry rags.

Surface to Be cleaned Oil and Grease Salt/Mud/Dust/Debris

Vehicle Exterior Detergent. Detergent.

Interior (Metal) Detergent. Detergent.

Glass Window Cleaning

Compound.

Window cleaning

compound.

Ballistic Glass Detergent; soapy

water; plastic polish;

dry rags.

Detergent; soapy water;

plastic polish; dry

rags.

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Plastic Windows Soapy Water; cream

cleaner; dry rags.

Soapy water, cream

cleaner; dry rags.

Vehicle Interior Water; damp and dry

rags.

Soapy water; damp and

dry rags.

Frame Detergent rinsed with

water; dry rags.

Soapy water; damp and

dry rags.

Engine and Trans-

mission

Drycleaning solvent;

water; rags.

Soapy water; soft wire

brush; damp and dry

rags.

Radiator Not Applicable. Low pressure water; air;

soapy water; damp anddry rags

Rubber Insulation Damp and dry rags. Damp and dry rags.

Tires Soapy water; dry rags. Soapy water; dry rags.

Wood Detergent; water; damp

and dry

rags.

Low pressure water;

soapy water; damp and

dry rags.

3. Fluid Leakage.

Wetness around gaskets, fittings, or connections indicates leakage of the

service liquid in the system. If a fitting or connector is loose, tighten

it. If the fitting or connector is broken or defective, report it to

organizational maintenance for replacement. Use the following guidelines

to determine if you should operate the vehicle with existing leakage:

a. Class I Leakage. This is leakage indicated by wetness or

discoloration not great enough to form drops. Operating the vehicle with a

Class I leak is allowable so long as the service fluid is not brake fluid.

b. Class II Leakage. This is leakage great enough to form drops, but

not so great as to cause drops to drip from the component being

checked/inspected. Vehicle may be operated with Class II leakage so long

as the service fluid is not fuel or brake fluid.

c. Class III Leakage. Class III is leakage great enough to cause

drops to fall from the item being checked/inspected.

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Operating a vehicle with a class III leak is prohibited and you must report

the leak immediately to organizational maintenance. Failure to report class

III leaks will result in damage to the vehicle and/or components.

Any brake fluid leakage must be reported immediately when it

is discovered. WHEN IN DOUBT, NOTIFY YOUR SUPERVISOR.

When you must operate vehicles with class I or II leaks, the

service fluid in the affected system must be checked more

frequently than is otherwise necessary. All leakage

discrepancies must be scheduled for organizational

maintenance corrective repair as soon as is practicable.

d. Engine Oil Servicing. The engine oil level is checked while the

engine is stopped. To ensure that oil cooler drain back oil does not give

a false reading, the engine should be operated for approximately 1 minute

prior to checking the oil. Perform the following steps to check the oil.

(1) Raise and secure hood.

(2) Then, pull out the engine oil dipstick and check for the

proper oil level.

The engine oil level should be at the crosshatch marks on the

dipstick between FULL and ADD 1 QT as shown in Figure 2-10.

If the oil level indicates anywhere in the crosshatched area

of the dipstick, the level is sufficient for operation. It

is important that you not overfill the engine crankcase.

Damage to the engine will result.

If the engine oil level indicates above the FULL mark on the

dipstick, operate the engine for approximately 1 minute to

evacuate drain back oil to the oil cooler. Then, shut down

the engine, wait 1 minute and recheck the oil level.

If the engine oil level is low, remove the oil filler cap and

add LO 9-2320-280-12 engine oil.

(3) Replace and tighten the oil filler cap and replace the engine oil

dipstick. Wipe up any oil which you may have spilled during the servicing

operation.

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Figure 2-10. Engine Oil Servicing.

4. Troubleshooting Procedures.

Vehicle troubleshooting will help you identify and correct simple vehicle

malfunctions and identify malfunctions which you must refer toorganizational maintenance.

a. Engine Fails to Crank. If the engine fails to crank when the

rotary switch is placed in the START position, the following conditions may

be the cause:

(1) Check to ensure that the transmission shift lever is in the

neutral (N) position. If not, place the lever in neutral.

(2) Check to see if the voltmeter is reading in the green area of

the gage.

If the voltmeter reads yellow or red, check the battery

electrolyte level and inspect the battery cable connections

for looseness, damage, or corrosion.

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If any of the above conditions exist, notify organizational

maintenance.

(3) Attempt to slave-start the vehicle. To do this, you

position the slaving vehicle close enough to permit hookup of

the slave cable.

ensure the slaving vehicle's engine is stopped.

remove the cover from the slave receptacle onboth vehicles.

Ensure that the battery cables on the disabled vehicle are

properly connected before connecting the slave cable. Damage

to batteries, cables, or serious injury to personnel may

result if battery cables are improperly connected. Make sure

electrical switches in both vehicles are turned off.

connect the slave cable to the slave receptacle of both

vehicles.

start the engine of the slaving vehicle.

start the disabled vehicle. After the engine starts,

disconnect the slave cable from both vehicles.

install the slave receptacle covers on both vehicles.

clean and stow the slave cable.

(4) If the foregoing actions fail to start the engine, the problem

is due to other causes and you should notify organizational maintenance.

b. Engine Cranks Slowly. If the engine cranks too slowly to start

when the rotary switch is turned to the START position, perform the

following:

(1) Check to see if the voltmeter reads green.

If the voltmeter reads yellow or red, check the battery fluid

level and battery connections for looseness, damage, orcorrosion.

If any of these conditions exist, notify organizational

maintenance.

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(2) Attempt to slave-start the vehicle as shown in paragraph

4.a. (3).

(3) If the engine still fails to start, the problem is due to

other causes and you should refer it to organizational maintenance.

c. Engine Cranks But Does Not Start. If the starter cranks the

engine at normal speed, but the engine still doesn't start, you perform the

following checks.

(1) Check to see if the fuel tank contains fuel. If the tank

gage reads empty (E), fill the tank and attempt to start the engine after

purging any air from the fuel system. Purging air from the fuel system is

necessary at any time the vehicle has run out of fuel. To do this, you

Raise and secure the hood.

Then, disconnect the fuel line (1) from the fuel filter outlet(2) (Figure 2-11).

Figure 2-11. Purging the Fuel System.

Now, place a rag over the fuel filter outlet and crank the

engine until the rag is wet with fuel.

Next, connect the fuel line to the fuel filter outlet securely.

Wipe up any fuel that may have spilled during the purging

operation. Dispose of fuel soaked rags in a covered container

approved for oily refuse.

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Then, attempt to start the engine. If the engine starts and

operates normally, close and secure the vehicle hood.

(2) Check to see if the WAIT-TO-START lamp assembly fails to

light, or doesn't go out.

Notify organizational maintenance if the WAIT-TO-START light

fails to light or doesn't go out.

(3) If the foregoing efforts fail to start the engine, the

problem is due to other causes. Organizational maintenance should be

notified.

d. Vehicle Does Not Charge According to the Voltmeter. If the

voltmeter indicates that the alternator is not charging the batteries in a

normal manner, perform the following troubleshooting steps:

(1) Check the battery cables for looseness, damage, orcorrosion. Notify organizational maintenance of any discrepancies.

(2) Check for broken or missing alternator drive belts. Notify

organizational maintenance if the alternator belts are broken or missing.

(3) If the foregoing efforts fail to correct the noncharging

discrepancy, the problem is due to other causes and you should notify

organizational maintenance.

e. Excessive Exhaust Smoke After Engine Reaches Normal Operating

Temperature. Some smoking is normal on a cold engine. If smoking

continues, however, after the engine has reached normal operatingtemperature of 190-230F. (88-110C.), you should take the following

troubleshooting steps:

(1) Check the engine oil level for an excessively high level.

Notify organizational maintenance if the oil level is above the FULL mark

on the oil dipstick.

(2) Check for restricted air cleaner.

If an emergency situation exists, clean the air cleaner

element as specified in lesson 1.

If an emergency situation does not exist, notify

organizational maintenance of the problem.

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(3) If the foregoing efforts fail to correct the smoking engine

discrepancy, the problem is due to other causes and organizational

maintenance should be notified.

f. Engine Starts But Misfires, Runs Rough, or Lacks Power. If the

engine runs roughly after it starts, problems may exist in the fuel or airinduction systems. If this problem is encountered, perform the following


(1) Check for water in the fuel system by draining the fuel filter

assembly at the fuel filter draincock.

Raise and secure the vehicle hood.

Start the engine and let it run at idle.

Open the fuel filter draincock and drain approximately 1

pint (0.47 liter) of fuel into a 1 quart glass container.

Close the draincock and inspect the fuel sample for

evidence of water in the fuel. If you find water in the

fuel, take a second sample to determine if water is still

present. If you find water in the second sample, notify

organizational as the fuel system is likely contaminated

with water.

If the second sample is free of water, shut off the

vehicle engine and secure the fuel filter draincock.

Then, lower and secure the vehicle hood.

(2) Check for a restricted air cleaner.

If an emergency situation exists, clean the air cleaner

element as specified in Lesson 1.

If an emergency situation does not exist, notify

organizational maintenance of the air restriction/rough

running engine problem.

(3) If the foregoing efforts fail to correct the rough running

engine discrepancy, the problem is due to other causes and you shouldnotify organizational maintenance.

g. Engine Overheats According to Engine Coolant Temperature Gage.

If the engine coolant temperature gage indicates greater than normal

operating temperature (190-230 F.) while the vehicle is in operation,

stop the vehicle and let the engine idle to see if the temperature comes

down to normal. If higher than normal operating temperatures persist,

perform the following troubleshooting steps:

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(1) First, raise and secure the vehicle hood and, while the

engine is running, check to see if the cooling system fan is operating. If

the cooling fan is not running, perform emergency fan clutch override

procedure as follows:

Figure 2-12. Engine Temperature Control Valve.

NOTE: The cooling system fan in the M998 series vehicle

normally activates when the engine temperature

exceeds 220F. and deactivates when the engine

operating temperature drops below 190F. The fan

override procedure will permit continuous fan

operation under emergency circumstances.

Stop the engine and locate the temperature control valve

(Figure 2-12) on the engine cowl next to the windshield

washer reservoir.

Disconnect the time delay module connector from the

control valve connector

Start the engine and watch for continuous cooling fan

operation. If the fan is not operating continuously, stop

the engine and notify organizational maintenance.

If the fan is operating continuously, close and secure the

vehicle hood.

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Allow the engine to cool at idle until the operating

temperature is between 190-230F. (88-110C.).

Proceed to organizational maintenance with the vehicle.

Make certain organizational maintenance is notified of the

emergency service that was performed on the vehicle.

(2) Allow the engine to cool and check the coolant level in the

coolant surge tank. Add coolant as necessary.

(3) Check for debris blocking the radiator cooling fins. Remove

any debris found.

(4) Check for broken or missing fan belts. Notify

organizational maintenance if the belts are broken or missing.

(5) If the foregoing efforts fail to correct the overheatingdiscrepancy, the problem is due to other causes and you should notify

organizational maintenance.

h. Low Engine Oil Pressure According to Oil Pressure Gage. If the

engine oil pressure fails to register, does not register a minimum of 6 psi

(41 kPa) at idle, or does not maintain 40-50 psi at normal operating

speeds, stop the vehicle and check the engine oil level. If the level is

low, add engine oil. If the dipstick indicates the engine oil level is

normal, notify organizational maintenance of the low oil pressure problem.

PART B - MAINTAIN THE FUEL SYSTEM

1. Fuel Filter Inspection After Operation.

After operating the HMMWV, check the fuel system for contamination. To

perform this inspection, you

a. raise and secure the vehicle hood.

b. start the engine and open the fuel filter draincock (Figure

2-13). Drain approximately 1 pint of fuel into a clear glass container

until the fuel runs clear. Inspect the fuel in the container for evidence

of water and/or foreign matter. Rotate the container causing the fuel to

swirl and form a vortex or whirlpool. Any sediment in the fuel will bevisible at the point of the vortex. Water contained in the fuel will be

visible as bubbles in the swirling fuel. If the fuel sample contains

contaminated fuel, take another sample to see if the contaminated fuel was

confined to the fuel filter. If contaminated fuel continues to be evident

in the fuel, notify organizational maintenance of the problem.

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Figure 2-13. Fuel Filter Draincock.

c. close and secure the fuel filter draincock.

d. inspect the engine for fuel leaks or evidence or discoloration

which indicates a fuel leak. The existence of a Class III leak indicates

that the vehicle is not ready for operation. Report any discrepanciesnoted during the inspection to organizational maintenance.

e. close and secure the vehicle hood.

2. Fuel Tank Servicing.

Do not perform fuel tank servicing or other fuel system maintenance while

smoking or near fire, flame, or sparks. Fuel may ignite causing damage to

the vehicle and injury or death to personnel. You must always stop the

engine while servicing the fuel tank. To service the fuel tank, you first

a. turn the handle on the fuel cap counterclockwise and remove thecap from the filter opening.

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Figure 2-14. Fuel Tank Servicing.

(1) The fuel tank filler cap is connected to the tank opening by

a retaining chain to prevent loss of the cap as shown in Figure 2-14. Use

care when removing the cap to prevent damaging the chain.

(2) If the fuel cap handle is turned more than is necessary to

remove the cap, the fuel cap backing plate may become jammed on the staked

threads of the cap. If this occurs, correct the problem by holding the cap

backing plate and turning the cap handle clockwise until the backing plate

turns freely.

b. Then, force the fuel nozzle into the filler neck rubber cone so

that a seal is formed between the nozzle and opening. Proceed with fueling

until the tank is full.

c. When the fueling operation is complete, install the fuel cap and

turn clockwise until sealed.

PART C - MAINTAIN THE TRANSMISSION

1. Transmission Data.

The M998 series Wheeled Vehicle is equipped with a three-speed Turbo Hydra-

Matic 400 automatic transmission. The transmission service fluid is Dexron

II automatic transmission fluid. The transmission is controlled by the

transmission shift lever which has five positions and four operating ranges

for varying operating conditions.

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The transmission does not have a park position. For this reason it is

important to stress that the parking brake MUST BE APPLIED at any time the

vehicle is stopped and the shift lever is in the N (Neutral) position. The

five selectable positions of the automatic transmission and intended

operating conditions are as follows:

a. (N) Neutral - Vehicle stopped with the parking brakeapplied.

b. (R) Reverse - Vehicle backing up while clear of traffic,

using a ground guide.

c. (D) Drive - Normal driving and fording.

d. (2) Second - Hill climbing and "engine braking" to slow

the vehicle when descending steep hills.

e. (1) First - Maximum "engine braking" when descending very

steep hills, climbing steep hills, or driving through deep mud, sand, orsnow.

2. Transmission Fluid Level.

You check the transmission fluid level weekly or whenever the transmission

malfunctions.

a. Checking the Transmission Fluid Level. Take the following

steps when checking the transmission:

(1) Make sure the transmission is at normal operating temperature

before checking the fluid level. It is best to perform this check afteroperation when the engine and transmission are at their normal operating

temperature.

(2) Use caution when servicing the transmission to avoid getting

any dirt, dust, or grit into the transmission oil

dipstick tube. Internal transmission damage will occur if the transmission

fluid supply becomes contaminated.

(3) Start the vehicle engine and apply the service brakes. While

holding the service brakes, move the transmission shift lever through all

the operating ranges including reverse. Then, shift into the "N" positionand apply the parking brake. With the engine at idle, remove the

transmission dipstick and check for the proper transmission fluid level.

Fluid level should indicate in the crosshatched area of the dipstick

(Figure 2-15).

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Figure 2-15. Transmission Fluid Level Dipstick.

(4) If the transmission fluid level is at or below the "ADD" mark

on the dipstick, add Dexron II transmission fluid as required to bring the

fluid to the required level. Do not overfill the transmission. Damage to

the transmission will result.

b. Transmission Fluid Servicing. Take the following steps to supply

fluid to the transmission.

(1) After raising and securing the hood, you start the engine and

allow it to run at idle.

(2) While depressing the service brake, move the transmission

shift lever through all ranges and "R" before checking the transmission

fluid level in "N" with the parking brake applied.

(3) Then, pull out the transmission dipstick (Figure 216) and

check for the proper transmission fluid level. At normal operating

temperature, fluid level should be at the dipstick cross hatch marks.

(4) If the transmission fluid level is low, add fluid through the

filler tube. Then, reinsert and secure the dipstick and wipe away any

spilled fluid. Then, close and secure the hood.

CAUTION: Do not overfill transmission. Damage to the

transmission will result.

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Figure 2-16. Transmission Fluid Servicing.

3. Transmission Checks.

You check the transmission shift linkage for binding daily. To perform the

required checks, apply the service brake pedal and shift the transmission

through all operating ranges and reverse while checking for binding of the

shift lever.

4. Transmission Troubleshooting.

If there is no response when you shift the transmission shift lever into an

operating range, and the vehicle remains stationary, perform the following


a. Shift Lever. Check to see if the transfer case shift lever

is in the neutral position. If it is not in neutral, place the

transmission shift lever in neutral and select the transfer gear. If the

transmission shift lever and transfer case shift lever are in the proper

position notify organizational maintenance.

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b. Rough Shifting. If the transmission shifts roughly and the

engine surges during operation, notify organizational maintenance.

c. Fluid Thrown from Transmission Fill Tube. Perform the following

troubleshooting steps if transmission fluid leakage is evident in the area

around the dipstick and transmission fill tube:

(1) Check to see if the transmission dipstick is loose. Secure

the dipstick and wipe away any fluid that may be present.

(2) Check the transmission fluid level for overfilling. Notify

organizational maintenance if the fluid level is too high.

(3) Refer other causes of fluid being thrown from the

transmission fill tube to organizational maintenance.

d. Slippage In All Ranges. If slippage and engine surge is noted

during operation, check the transmission for low fluid level and servicethe transmission as appropriate. Refer all other causes of transmission

slippage to organizational maintenance.

PART D - MAINTAIN THE STEERING SYSTEM

1. Checking the Power Steering Reservoir.

Power steering system Preventive Maintenance Checks and Services are

required on a weekly basis. You perform the following checks, and repair,

fill, or adjust as necessary:

a. Inspect the drive belts for missing, cracking, fraying, andbreaks. Report any discrepancies noted to organizational maintenance.

b. Then, inspect the power steering pump assembly for leaks and

mounting hardware. The vehicle is not ready for operation if you notice

Class III.

c. Now, check the power steering reservoir fluid level for he

proper fluid level.

2. Power Steering Fluid Servicing.

Perform the following steps to service the power steering fluid reservoir:

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Figure 2-17. Power Steering Fluid Servicing.

a. Raise and secure the vehicle hood.

CAUTION: Do not permit dirt, dust, or grit to enter the power

steering reservoir. Damage to the power steering systemwill result.

b. Pull out the reservoir cap/dipstick (Figure 2-17) and check the

power steering reservoir fluid level.

(1) If the engine is warm, fluid level should be between the

dipstick HOT and COLD marks.

(2) If the engine is cold, the reservoir fluid level should be

between dipstick ADD and COLD marks.

c. If the fluid level is low, add fluid to the power steering

reservoir. Use caution not to overfill the power steering reservoir.

Damage to the system will result.

d. Now, install the cap/dipstick and wipe away any spilled fluid.

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Refer other causes of excessive or uneven tire pressure to

organizational maintenance for correction.

b. Troubleshooting Problems in Steering. Perform the following

troubleshooting steps if you encounter these conditions:

(1) Vehicle Wanders to One Side on Level Payment.

Check the tire air pressure. Inflate or deflate the tires

to correct the pressure.

Refer other causes of vehicle wandering to organizational

maintenance for correction.

(2) Hard Steering.

Check the tire air pressure. Inflate or deflate the tires

to the correct pressure.

Check the power steering reservoir for low fluid level.

Service the reservoir to the proper level.

Check for broken or missing power steering belts.

Notify organizational maintenance if belts are broken or

missing.

Refer other causes of hard steering to organizationalmaintenance for correction.

4. Shock Absorbers.

Shock absorbers located at each wheel help to steady the vehicle in

operation. If unusual handling, dip, or sway is noted during operation,

check the shock absorbers for leakage or damage. Do not operate the

vehicle if you notice Class III leakage. Conduct a visual inspection of

the shock absorbers for leakage or broken/missing parts monthly.

5. Wheel Assembly Replacement.

When it becomes necessary to remove a wheel from the vehicle, use the

following procedures:

a. Wheel Assembly Removal. Before beginning to remove the wheel

from the vehicle (Figure 2-19), apply the parking brake and block the

opposite wheel. Remove a wheel only on level terrain.

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(1) Place the vehicle jack assembly under the suspension control

arm of the wheel being removed. Ensure the jack is firmly set squarely

under the point of contact with the control arm. Do not raise the wheel

completely off the ground.

Figure 2-19. Wheel Assembly Replacement.

(2) Loosen the eight lug nuts holding the wheel on the wheel

hub..Loosen only the inner group of nuts (Figure 2-19). The nuts on the

outer circumference of the wheel hold the split rim of the wheel assembly

together. Removal of these nuts while the tire is inflated could result in

injury or death.

(3) Raise the vehicle high enough to permit removal of the wheel.

(4) Remove the eight lug nuts securing the wheel assembly to the

geared hu b. Remove the wheel assembly from the vehicle.

b. Wheel Assembly Installation.

(1) Install the wheel assembly on the geared hub taking care not to

damage the threads on the lugs. Secure the wheel in place with eight lug

nuts. Ensure that the wheel attains full engagement with the geared hub.

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(2) Slowly lower the vehicle to the ground and remove the jack.

(3) Tighten the lug nuts in the order indicated in Figure 2-20.

Figure 2-20. Wheel Lug Tightening Sequence.

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LESSON 2

Practice Exercise

The following items will test your knowledge of the material covered inthis lesson. There is only one correct answer for each item. When you

have completed the exercise, check your answers with the answer key that

follows. If you answer any item incorrectly, study again that part of the

lesson which contains the portion involved.

Situation: You are an M998 Wheeled Vehicle operator assigned to a field

unit. Your unit has just completed an operation. During that operation,

you noticed several faults with your vehicle that require immediate

attention along with regularly scheduled maintenance in preparation for the

next operation.

1. The engine in your vehicle will not crank when you attempt to start theengine. When you check the voltmeter it reads

yellow. Immediately you

A. tap the cover on the voltmeter to physically check the battery

level reading.

B. recycle the start switch to RUN, then START to retry starting the

engine.

C. check the battery fluid level, then check the cables for looseness,

damage or corrosion.

D. get help to push start the vehicle and charge the battery.

2. Just as you are starting to check the fuel filter on your vehicle, oneof your fellow soldiers lights up a cigarette. Immediately you

A. inform him not to blow smoke in your direction.

B. inform him that he can smoke but to move when lighting a match.

C. inform him that he must sit in the vehicle while smoking.

D. inform him that he must put out his cigarette.

3. Your vehicle has run out of fuel. After you complete refueling, you

A. purge the fuel system of any air.

B. clean the fuel filter.

C. schedule organizational level fuel filter maintenance.D. crank the engine to cycle fuel into the engine.

4. Before performing checks of the transmission fluid level, you

A. turn off the engine and let it cool down.

B. run the engine at idle with the transmission in "N".

C. run the engine at idle with the transmission in "D".

D. turn off the engine and perform the check while it is still hot.

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5. You have just serviced your transmission but when you start the

vehicle, transmission fluid is being thrown from the engine. You

immediately shut down the engine and check for a/an

A. low transmission fluid level.

B. transfer case shift lever in "N".C. overfilled transmission fluid level.

D. low engine oil level.

Figure 2-21.

6. Refer to Figure 2-21. Identify the proper level of the power steering

reservoir in a warm to hot engine.

A. 1.

B. 2.C. 3.

D. 4.

7. During the operation, you notice that your front wheels wobble. To

ensure that the vehicle will handle better in the future, you

A. check the front tires for excessive wear.

B. check the front tires for low pressure.

C. check the front end for worn shock absorbers.

D. check the front wheels for loose lug nuts.

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LESSON 2

PRACTICE EXERCISE

ANSWER KEY AND FEEDBACK

Item Correct Answer and Feedback

1. C. check the battery fluid level, then check the cables

for looseness, damage, or corrosion.

Any time the voltmeter reads yellow or red, you check

those items and refer the vehicle to maintenance if any of

the listed conditions exist. (Page 37, para 4.a (2)).

2. D. inform him that he must put out his cigarette.

Safety precautions do not allow smoking or open flame near

gasoline. (Page 42, para 2).

3. A. purge the fuel system of any air.

Air in the fuel system can prevent the engine from running

properly. Any time the vehicle runs out of fuel, it can

get air in the fuel system, which must be purged. (Page

39, para 4.c (1)).

4. B. run the engine at idle with the transmission in "N".

With the engine running and the parking brake applied, put

the transmission in "N". Then, pull out the dipstick and

check to see that the fluid level is at the markings on

the dipstick. (Page 46, para 2.a (3)).

5. C. overfilled transmission fluid level.

Since you have just serviced the transmission, it is

likely that you have overfilled it. Check the

transmission fluid level to be sure of the cause, and

refer to organizational maintenance for correction. (Page

49, para 4.c (2)).

6. A. 1.

The proper level is between the HOT and COLD marks on the

dipstick. (Page 50, para 2.b (1)).

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7. D. check the front wheels for loose lug nuts.

Tighten any loose lug nuts and refer to organizational

maintenance to torque them to specifications. (Page 51,

para 3.a (1)).

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THIS PAGE IS INTENTIONALLY LEFT BLANK

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LESSON 3

START THE M998 WHEELED VEHICLE USING AUXILIARY POWER,

OPERATE AND MAINTAIN THE NBC SYSTEM,

AND CONDUCT TOWING OPERATIONS


OVERVIEW

LESSON DESCRIPTION

In this lesson you will learn how to start the M998 Wheeled Vehicle using

auxiliary power, operate and maintain the NBC system, and conduct towing

operations using the M998 Wheeled Vehicle.


ACTION: Wheeled Vehicle with auxiliary power, operating and

maintaining the NBC system, and conducting towing operationsusing the M998 Wheeled Vehicle.


STANDARD: Starting the M998 Wheeled Vehicle, operating the NBC system,

and conducting towing operations.

REFERENCE: The material contained in this lesson was derived from the

following publication:

TM 9-2320-280-10

INTRODUCTION

In addition to normal operation of the M998 Wheeled Vehicle, you must be

ready to operate in adverse conditions that may require you to start the

M998 using auxiliary power, operate and maintain the NBC system, or conduct

various types of towing operations. Upon completion of this lesson you will

be able to identify procedures used when starting the M998 Wheeled Vehicle

using auxiliary power, operating and maintaining the NBC system, and

conducting various types of towing operations.

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PART A - START AN M998 WHEELED VEHICLE USING AUXILIARY POWER

Slave Starting Operation.

At times you may need assistance in starting your HMMWV. Use the following

procedures to slave start your vehicle.

a. Position the slaving vehicle close enough to permit you

to hookup the slave cable.

b. Ensure that the slaving vehicle's engine is stopped.

c. Then, remove the cover from the slave receptacle on both

vehicles.

WARNING: Make sure that the battery cables on the disabled

vehicle are properly connected before connecting

the slave cable. Damage to batteries, cables, or

serious injury to personnel may result if batterycables are improperly connected. Make sure

electrical switches in both vehicles are turned

off.

d. Next, you connect the slave cable to the slave receptacle of both

vehicles.

e. Now, start the engine of the slaving vehicle.

f. Start the disabled vehicle. You learned the proper starting

procedures in lesson 1. After the engine starts, disconnect the slave

cable from both vehicles.

g. Then, install the slave receptacle covers on both vehicles.

h. The final step is to clean and stow the slave cable.

PART B - OPERATE AND MAINTAIN THE NBC SYSTEM

ON AN M996, M997 SERIES VEHICLE

1. NBC System Configuration.

a. General Information. For operation in a Nuclear, Biological,

Chemical environment, M996 and M997 ambulances are equipped with a

collective NBC protection system known as a GasParticulate Filter Unit

(GPFU). This protection system filters NBC contaminants from the air and

feeds filtered, temperature controlled air to the facepiece of the M25

series protective mask or the M13 patient protective mask. This increases

NBC protection, eases breathing effort, and reduces stress and heat fatigue

during extended periods of NBC operation.

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The GPFU system is mounted in M996 and M997 series vehicles and includes

the following components:

M1A1-19 precleaner (blower)/particulate filter unit.

MA18 gas filters (two per vehicle).

NBC control panel and wiring harness.

Five or seven individual NBC heaters.

PVC or flex tubing to connect filter

precleaner/particulate filters and heaters.

b. Warnings and Safety Precautions. You should be aware of the

following warnings and safety procedures.

(1) It is important you understand that NBC systems on the M996 and

M997 series vehicles do not decontaminate or neutralize contaminants in

breathing air. The system only collects and contains the contaminants. It

is also important that you do not have a false sense of security by

believing that you and your passengers are completely protected from the

harmful effects of NBC agents while using the system.

(2) NBC filters do not protect you or your passengers from carbon

monoxide poisoning.

(3) NBC contaminated filters must be handled using adequate safety

precautions and they must be disposed of by trained NBC personnel only.

(4) After NBC exposure of the vehicle, all air filters must be

handled with extreme caution. Unprotected personnel may experience injury

or death if residual toxic agents or radioactive material are present.

Servicing personnel must wear protective overgarments, mask, hood, and

chemical protective gloves and boots. Contaminated air filters will be

placed into double lined plastic bags and moved immediately to a temporary

segregation area away from the work site. Final disposal of NBC

contaminated air filters are in accordance w

US Army Mechanic Course - Maintenance of Wheeled Vehicle M998 (HMMWV) IN0511

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