Halderman ch023 lecture

© 2011 Pearson Education, Inc.All Rights Reserved

Automotive Technology, Fourth EditionJames Halderman

LUBRICATION SYSTEM OPERATION AND

DIAGNOSIS

23

23 LUBRICATION SYSTEM OPERATION AND DIAGNOSIS



ObjectivesObjectives

• The student should be able to:– Prepare for ASE Engine Repair (A1)

certification test content area “D” (Lubrication and Cooling Systems Diagnosis and Repair).

– Explain hydrodynamic lubrication.




ObjectivesObjectives

• The student should be able to:– Describe how the oil pump and engine

lubrication work. – Discuss how oil flows to the valve train

components. – Explain how to inspect an oil pump for

wear.




INTRODUCTIONINTRODUCTION




IntroductionIntroduction

• Purpose of Lubrication System– Lubricating all moving parts to prevent

wear– Helping cool the engine





• Purpose of Lubrication System– Helping seal piston rings– Cleaning and holding dirt in suspension





• Purpose of Lubrication System– Neutralizing acids formed as the result of

combustion– Reducing friction– Preventing rust and corrosion




LUBRICATION LUBRICATION PRINCIPLESPRINCIPLES




Lubrication PrinciplesLubrication Principles

• Purpose and Function– Lubrication creates oil film to separate

surfaces and support load




Figure 23-1 Oil molecules cling to metal surfaces but easily slide against each other.





• Purpose and Function– Oil does not compress but may leak out

between shaft and bearing– Under some conditions, oil keeps surfaces

from seizing but some contact occurs• Condition called boundary lubrication





• Purpose and Function– Viscosity and oil clearances help prevent

boundary lubrication and wear– Boundary lubrication usually occurs under

heavy load and at low speed





• Purpose and Function– Lubrication occurs as wedge-shaped oil film

builds between object and surface




Figure 23-2 Wedge-shaped oil film developed below a moving block.





• Hydrodynamic Lubrication– Wedging action of lubricant called

hydrodynamic lubrication– Depends on force applied to rate of speed

between objects and thickness of oil





• Hydrodynamic Lubrication– Thickness of oil is called viscosity– Viscosity is the ability of oil to resist flow– Prefix hydro- refers to liquids





• Hydrodynamic Lubrication– Dynamic refers to moving materials– Hydrodynamic lubrication occurs when

wedge-shaped film of oil develops between two surfaces that are moving




Figure 23-3 Wedge-shaped oil film curved around a bearing journal.





• Hydrodynamic Lubrication– Engine oil pressure system feeds oil into

the lighted loaded part of bearing oil clearance





• Hydrodynamic Lubrication– Hydrodynamic lubrication takes over as

shaft rotates in bearing to produce hydrodynamic oil film





• Hydrodynamic Lubrication– Pressure between bearings and crankshaft

can exceed 1,000 PSI (6,900 kPa) due to wedging action




ENGINE LUBRICATIONENGINE LUBRICATIONSYSTEMSSYSTEMS




Engine Lubrication SystemsEngine Lubrication Systems

• Purpose and Function– Primary purpose of lubrication system is to

maintain continuous oil supply to bearings





• Purpose and Function– Oil pressure must be high enough to get oil

to bearings with force needed for proper cooling





• Normal Oil Pressure– Normal engine oil pressure is from 10 to 60

PSI (200 to 400 kPa), or 10 PSI per 1000 engine RPM





• Normal Oil Pressure– Higher oil pressure occurs when engine is

cold due to higher viscosity of cold oil– Lower oil pressure occurs when at normal

operating temperature





• Normal Oil Pressure– Lower oil pressure at idle and higher

pressure at higher engine speeds because oil pumps are “positive displacement” pumps





• Normal Oil Pressure– Oil pressure measurements show oil pump

pressure, not pressure due to hydrodynamic forces




Figure 23-4 The dash oil pressure gauge may be a good indicator of engine oil pressure. If there is any concern about the oil pressure, always use a mechanical gauge to be sure.





• Oil Temperature– Excessive high or low temperatures are

harmful to engine– Too cold and oil becomes too thick to flow

and lubricate engine parts





• Oil Temperature– Too hot and oil becomes too thin to provide

sufficient film strength– Estimated oil temperature

• Estimated oil temperature = Outside air temperature + 120°F





• Oil Temperature– Oil temperature should not exceed 300°F

(150°C)




OIL PUMPSOIL PUMPS




Oil PumpsOil Pumps

• Purpose and Function– Provide 3 to 6 gallons of oil per minute– Maintain pressure to force oil through

lubrication system




Oil PumpsOil Pumps

• Parts and Operation– In most engines with distributor, distributor

drive gear meshes with gear on camshaft




Figure 23-5 An oil pump driven by the camshaft.




Oil PumpsOil Pumps

• Parts and Operation– Oil pump is driven from end of distributor

shaft – Distributor-driven oil pump turns pump at

one-half engine speed




Oil PumpsOil Pumps

• Parts and Operation– On crankshaft-drive oil pump systems, oil

pump turns at same speed as crankshaft




Oil PumpsOil Pumps

• Types of Oil Pumps– All oil pumps are positive displacement

pumps– Each rotation delivers same volume of oil– Delivers oil at higher pressure as speed of

pump increases




Oil PumpsOil Pumps

• Types of Oil Pumps– Two types of oil pumps: gear or rotor– External gear type

• Usually driven by shaft from distributor




Oil PumpsOil Pumps

• Types of Oil Pumps– External gear type

• Rotates at half crankshaft speed• Consists of two spur gears—one gear is

driven while one is idle




Oil PumpsOil Pumps


• As gear teeth come out of mesh, they are filled by oil from pump inlet




Oil PumpsOil Pumps


• When pump pumps, soil goes outside of each gear between gear teeth and housing




Oil PumpsOil Pumps


• As teeth mesh, oil is forced into oil passage creating pressure




Figure 23-6 In an external gear-type oil pump, the oil flows through the pump around the outside of each gear. This is an example of a positive displacement pump, wherein everything entering the pump must leave the pump.




Oil PumpsOil Pumps

• Types of Oil Pumps– Internal/external gear type

• Driven by crankshaft and operates at engine speed

• Two gears and crescent stationary element used




Figure 23-7 A typical internal/external oil pump mounted in the front cover of the engine that is driven by the crankshaft.




Oil PumpsOil Pumps

• Types of Oil Pumps– Rotor type

• Driven by crankshaft• Uses lobe-shape gear meshing with inside of

lobed rotor




Oil PumpsOil Pumps


• Center lobed section is driven; outer section idles

• As lobes separate, oil is drawn in




Oil PumpsOil Pumps


• As pump rotates, oil is carried between lobes

• As lobes mesh, they force oil out from between them under pressure




Oil PumpsOil Pumps


• Pump maintains pressure of at least 10 PSI (70 kPa) when engine is hot and idling




Figure 23-8 The operation of a rotor-type oil pump.




Oil PumpsOil Pumps

• Types of Oil Pumps– Gerotor type

• Uses inner and outer rotor• Term derived from “generated rotor”




Oil PumpsOil Pumps

• Types of Oil Pumps– Gerotor type

• Inner rotor has one fewer teeth than outer rotor

• Both rotors rotate




Figure 23-9 Gerotor-type oil pump driven by the crankshaft.




Oil PumpsOil Pumps

• Oil Pressure Regulation– Maximum pressure is limited with pressure

relief valve– Relief valve sometimes called pressure

regulating valve– Relief valve limits maximum pressure by

bleeding oil to inlet side of pump




Figure 23-10 Oil pressure relief valves are spring loaded. The stronger the spring tension, the higher the oil pressure.




Oil PumpsOil Pumps

• Oil Pressure Regulation– Relief valve spring tension determines

maximum oil pressure– Without relief valve, oil pressure increases

as engine speed increases




Oil PumpsOil Pumps

• Oil Pressure Regulation– Oil pump large enough to provide pressure

a low engine speeds– Oil pump small enough so it won’t cavitate

at high speed




Oil PumpsOil Pumps

• Oil Pressure Regulation– Cavitation occurs when pump pulls oil

faster than it can flow from pan to pickup– When pump cannot get enough oil, it pulls

air




Oil PumpsOil Pumps

• Oil Pressure Regulation– NOTE: Sheet metal covers over pickup

screen prevent cavitation. Oil under cover helps prevent pump from drawing air.

– Oil from pump flows through oil filter and then to moving parts




Figure 23-11 A typical engine design that uses both pressure and splash lubrication. Oil travels under pressure through the galleries (passages) to reach the top of the engine. Other parts are lubricated as the oil flows back down into the oil pan or is splashed onto parts.




Oil PumpsOil Pumps

• Factors Affecting Oil Pressure– Leaks

• Leaks are clearances at end points of lubrication system




Oil PumpsOil Pumps


• These clearances are necessary for proper engine operation




Oil PumpsOil Pumps


• As parts wear, leaks become greater and oil pressure drops




Oil PumpsOil Pumps

• Factors Affecting Oil Pressure– Oil pump capacity

• Oil pump must supply extra oil for leaks




Oil PumpsOil Pumps


• Capacity of oil pump determined by size, rotating speed, condition




Oil PumpsOil Pumps


• If leaks are greater than pump capacity, oil pressure is low




Oil PumpsOil Pumps


• Higher engine speed increases capacity of pump to force oil out of leaks




Oil PumpsOil Pumps


• NOTE: Clogged oil pump pickup screen can cause lower oil pressure.




Oil PumpsOil Pumps

• Factors Affecting Oil Pressure– Viscosity of engine oil

• Viscosity affects pump capacity and leakage




Oil PumpsOil Pumps


• Oil with low viscosity slips past edges of pump and flows freely from leaks




Oil PumpsOil Pumps


• Hot oil has low viscosity so hot engine has lower oil pressure




Oil PumpsOil Pumps


• Cold oil is more viscous resulting in higher pressures




Oil PumpsOil Pumps


• Higher viscosity oil raises oil pressure to regulating setting of relief valve at a lower engine speed

?




Oil PumpsOil Pumps

• Oil Pump Checks– Cover is removed to check condition of oil

pump– Visual inspection

• Inspect gears and housing for scoring




Oil PumpsOil Pumps

• Oil Pump Checks– Visual inspection

• Replace pump if heavy scoring apparent




Figure 23-12 (a) A visual inspection indicated that this pump cover was worn.




Figure 23-12 (b) An embedded particle of something was found on one of the gears, making this pump worthless except for scrap metal.




Oil PumpsOil Pumps

• Oil Pump Checks– Measurements

• If light scoring, measure pump clearances• Feeler gauge often used for measurements




Oil PumpsOil Pumps


• Gauging plastic used to measure space between side of gears and cover




Oil PumpsOil Pumps


• Replace if excessive clearance or scoring is found




Oil PumpsOil Pumps

• Oil Pump Checks– NOTE: Oil pump is “garbage pit” of engine.

Debris is often forced through the gears and housing.




Figure 23-13 (a) The oil pump is the only part in an engine that gets unfiltered engine oil. The oil is drawn up from the bottom of the oil pan and is pressurized before flowing to the oil filter.




Figure 23-13 (b) If debris gets into an oil pump, the drive or distributor shaft can twist and/or break. When this occurs, the engine will lose all oil pressure.




Oil PumpsOil Pumps

• Oil Pump Checks– Refer to manufacturer’s specifications

when checking pump for wear– Typical pump clearances

• End plate clearance: 0.0015 in. (0.04 mm)




Oil PumpsOil Pumps

• Oil Pump Checks– Typical pump clearances

• Side (rotor) clearance: 0.012 in. (0.30 mm)




Oil PumpsOil Pumps


• Rotor tip clearance: 0.010 in. (0.25 mm)




Oil PumpsOil Pumps


• Gear end play clearance: 0.004 in. (0.10 mm)




Oil PumpsOil Pumps

• Oil Pump Checks– Check all parts– Check relief valve for scoring




Oil PumpsOil Pumps

• Oil Pump Checks– Check condition of relief valve spring– When installing oil pump, coat sealing

surfaces with engine assembly lubricant




OIL PASSAGESOIL PASSAGES




Oil PassagesOil Passages

• Purpose and Function– Oil from pump first flows through oil filter– Oil then flows through drilled hole to drilled

main oil gallery• Inline engines use one oil gallery





• Purpose and Function– Oil then flows through drilled hole to drilled

main oil gallery• V-type engines may use two or three

galleries





• Purpose and Function– Passages drilled through block bulkheads

allow oil to go from main oil gallery to main and cam bearings




Figure 23-14 An intermediate shaft drives the oil pump on this overhead camshaft engine. Note the main gallery and other drilled passages in the block and cylinder head.





• Purpose and Function– In some engines, oil goes to cam bearings

first, then to main bearings– Oil holes in bearings must match drilled

passages





• Purpose and Function– Over time, bearings wear– Excess clearance allows excess leakage

around sides of bearings





• Purpose and Function– Little or no oil may be left for bearings

downstream in lubricating system– Bearing failure may result





• Valve Train Lubrication – Oil gallery may intersect or have drilled

passages to valve lifter bores– With hydraulic lifters, oil pressure in gallery

keeps them lubricated





• Valve Train Lubrication – On some engines, oil from lifters goes up

center of hollow pushrod to lubricate pushrod ends, rocker arm pivot, and valve stem tip





• Valve Train Lubrication – In other engines, drilled oil passage from

gallery or cam bearings leads to head gasket hole and drilled hole to carry oil to rocker arm shaft

– Some engines used enlarged bolt hold to rocker arm shaft





• Valve Train Lubrication– Holes in bottom of rocker arm shaft allow

lubrication of rocker arm pivot– Rocker arm assemblies need only surface

coating of oil• Restrictions or metered openings restrict oil

flow





• Valve Train Lubrication– Oil from rocker assemblies returns to oil

pan through drain holes– Oil drain holes often drain oil on camshaft

or cam drive gears




Figure 23-15 Oil is sent to the rocker arms on this Chevrolet V-8 engine through the hollow pushrods. The oil returns to the oil pan through the oil drainback holes in the cylinder head.





• Valve Train Lubrication– Some engines direct positive oil flow to

cam drive gears or chain• Nozzle





• Valve Train Lubrication– Some engines direct positive oil flow to

cam drive gears or chain• Chamfer on bearing parting surface




OIL PANSOIL PANS




Oil Pans Oil Pans

• Purpose and Function– Oil pan, or sump, is where engine oil is

used for lubricating engine– Pan baffles and oil pan shapes keep oil inlet

under oil at all times




Oil Pans Oil Pans

• Purpose and Function– Crankshaft rotation can churn oil causing

air bubbles in oil and foaming– Baffle or windage tray is sometimes used to

eliminate oil churning

?




Figure 23-16 A typical oil pan with a built-in windage tray used to keep oil from being churned up by the rotating crankshaft.




DRY SUMP SYSTEMDRY SUMP SYSTEM




Dry Sump SystemDry Sump System

• Construction and Operation– Sump describes location where oil is stored– Most engines hold oil in oil pan; pump

draws oil from bottom





• Construction and Operation– This system is called a wet sump oil system– Dry sump system uses shallow pan

• Oil is pumped into remote reservoir





• Construction and Operation– Dry sump system uses shallow pan

• Oil is cooled and trapped air escapes





• Construction and Operation– Dry sump system uses shallow pan

• Dry sump uses externally mounted oil reservoir





• Advantages– Advantages of dry sump system

• Shallow pan allows engine to be mounted lower, improving cornering






• Oil capacity can be expanded because reservoir is not limited






• Vehicle can corner or brake for long periods






• Engine can develop more power because oil is kept away from crankshaft





• Disadvantages– Disadvantages of dry sump system

• Expensive because it needs extra components and plumbing





• Disadvantages– Disadvantages of dry sump system

• Complex because it creates more possibilities for oil leaks and changes routine maintenance




Figure 23-17 A dry sump system as used in a Chevrolet Corvette.




OIL COOLERSOIL COOLERS




Oil CoolersOil Coolers

• Larger capacity oil pan helps control oil temperature

• Remote mounted oil coolers– Warm oil in cold weather– Cool oil when engine is hot




Oil CoolersOil Coolers

• Oil Temperature– Above 212°F (100°C)– Below 280°F to 300°F (138°C to 148°C)

?




Figure 23-18 Oil is cooled by the flow of coolant through the oil filter adapter.

Halderman ch023 lecture

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