zeljko nastasic

Situacija je ista kao kod svih drugih hidraulickih Citroena osim C5 - istrosen ventil kocnice. Isto tako je vjerojatno prazna kugla od anti-sink sistema, za koju vecina servisa nema pojam da uopce postoji (jer je na nedostupnom mjestu).

Anti-sink ventil funkcionira na temelju razlike tlaka izmedju ovjesa i akumulatora, i to tako da izolira zadnji ovjes od ostatka sustava (ukljucivo korektor visine) kada tlak akumulatora padne ispod tlaka u ovjesu. Problem nastupa kada gubitak tlaka u ovjesu predstavlja najveci gubitak u sistemu, obicno cest slucaj kod zadnjeg ovjesa, zbog 'curenja' tlaka u povrat kroz ventil kocenja. U tom slucaju odmah u startu korektor se postavlja tako da tlak iz akumulatora nadoknadjuje gubitak tlaka u zadnjem ovjesu, i ako je gubitak dovoljno velik, tlak u ovjesu pada jednako kao i tlak u akumulatoru. Razlika tlakova potrebna za aktiviranje anti-sink ventila ne postoji i isti se nece aktivirati, dakle, zadnji kraj ce jos jedno vrijeme stajati dok se ne potrosi ono sto je u akumulatoru, a zatim ce pasti, jer ce se sav tlak 'potrositi' kroz ventil kocnice. Bas da bi se sprijecila ta situacija je ugradjena dodatna anti-sink kugla samo za zadnji ovjes, koja 'pokriva' gubitke kroz ventil kocnice kako bi se osigurao normalan rad anti-sink ventila.

Greska na nasem autu nastupa kada je ili gubitak kroz ventil kocnice prevelik, ili je dodatna anti-sink kugla prazna i ne moze pokriti gubitak kroz ventil kocnice (dakle sedma kugla kod DIRASS upravljanja ili osma kod DIRAVI). Nalazi se izmedju zadnjeg mosta i karoserije ako se dobro sjecam, blize desnom kotacu, i manje je velicine (slicno kao kugle za GS ili ekstra akumulator kocnice na XM DIRASS). Naravno, moze biti u pitanju mjesavina oba uzroka.

Napomena: anti-sink kugla se ne moze skinuti ako za to nije ucinjena ispravna procedura ispustanja tlaka iz ovjesa, dakle ovjes mora biti u 'tvrdom' rezimu i u najnizem polozaju prilikom ispustanja tlaka iz akumulatora (zatvoriti sva vrata i pustiti auto da radi oko 2-3 minute, zatim spustiti ovjes i pricekati oko 5 minuta da 'legne na zemlju' do kraja, zatim ispustiti tlak iz akumulatora, i tek onda ugasiti motor). Ako se ova procedura ne postuje, u anti-sink kugli zaostaje tlak. Ovo nije veliki problem kod auta kod kojih postoji vece curenje u ventilu kocnice, jer ce se ta kugla isprazniti kroz njega (no moze trajati i do par sati!), no kod novijih vozila, zaostali tlak moze biti opasan.

Moguce the da se situacija donekle popravi upotrebom Hydraurinceage-a, dakle ispiranjem sustava, jer ce se ocistiti zmazanoca u anti-sink ventilu, pa ce razlika tlaka za aktiviranje biti smanjena. No ako je zaista ventil kocnice istrosen, kad se isti zamijeni novim LHM-om, situacija ce biti gora jer ce se curenje kroz njega pojacati, jer vise nema nakupljene necistoce koja je 'na putu'. Kod ove greske prednji ovjes nikada ne pada jer se za njega aktivira ispravno anti-sink: u prednjem ovjesu je gubitak tlaka najmanji i tlak u njemu pada sporije od tlaka akumulatora.

Kod zamjene ventila kocnice treba znati da je jednak na CX serija II, BX, XM

i Xantia, razlikuje se samo polozaj cepa za odzracivanje.

Nadam se da ce vam ovo pomoci.

Pozdrav,

Z(eljko)

XM Suspension and Hydraulics

Various suspension systems

The differences between the various Hydractive systems are subtle in principle but great in execution.

Hydractive I

In addition to the standard suspension setup with struts and spheres, this first hydractive system uses two additionalspheres and a single electric valve which sends LHM at a pressure of 150 bars to the middle sphere support, moving aplunger that opens or closes. The suspension computer operates the valve using DC current; if you open the windows onthe side of the valve and press on the throttle or brake, you can clearly hear a rather loud click, almost as loud as thepressure regulator.

The default mode of the electronics (where it reverts to in case of a sensor or computer self-diagnostic failure) is hard.The default mechanical mode is, however, soft-if you pull off the connectors from the computer thus preventingactivation of the electric valve, the system remains in soft mode. During normal driving, the computer keeps thesuspension in soft mode most of the time but-based on the input provided by many sensors, (steering wheel, acceleratorpedal, body movement, road speed and brake) including the Sport/Comfort switch on the dashboard-the suspension ECUdecides when to deactivate the additional spheres for roadholding and safety.

Any malfunction will revert the car to the hard, not too comfortable but safe suspension mode. This also means thatwhenever you turn off the car, the suspension goes back into hard mode to prevent excessive sink or leap as passengers getin or out (this is also triggered by opening any door or the tailgate even with the engine running). After about a minute youcan hear the valve click again opening so that no pressure remains in the middle spheres once the suspension startsdepressurising.

With the additional spheres switched into the system, the car rides in soft mode on all three spheres per axle. When theyare cut off by the computer, it's not only the additional spheres which are decoupled from the system but the cornerspheres are totally isolated, without any LHM flowing from one side to the other, giving a hard, firm ride.

Switching to Sport overrides the computer and leaves the system in hard mode constantly, which is practically unusuablefor normal driving. Actually, the hard mode being so hard is due to a rather serious design flaw. All of the roll damping ofthe body is provided only by the damper assembly in the strut spheres. As a consequence, the strut spheres have very smallopenings. Using spheres with a larger opening would give a softer ride in hard mode but at the expense of a lot more roll ofthe body.

Three different computers were used during the years to serve the Hydractive I system. H1 appeared with the first XM. Ifyou open the computer box on the right side of the engine compartment, you'll find external anti-jolt diodes (black plasticcylinders of about 2" long) fitted. From ORGA 4859 on, a new H2 computer was used with internal diodes, with "H2"stamped on top. At ORGA 5539 the computer was changed to H3 and what's more important, the troublesome earthingblocks were replaced by simple, reliable ring connectors secured with a nut to the front wing.

Hydractive II

The second system introduced at ORGA 5929 uses completely different middle sphere supports that have the electrovalveintegrated in them (often referred to as "Xantia type" because that's where they were first introduced). These stiffnessregulator blocks also use different spheres, without the damping block, and also smaller. The damping blocks areintegrated into the regulator, they also have a one-way damping characteristic like the ones on the spheres. Logically, theopening and closing of the valves operates similarly to the Hydractive I but there are two valves now, operatedsimultaneously.

One big difference that results in the sport setting on Hydractive II actually being usable is the addition of a crossflowstopper in the regulator module. This is actually a little steel ball that rolls around in the cavity between the left and rightdamping assembly. When the car leans to the side, there is significant flow from the left to the right, that moves the ball sothat it actually stops the flow of LHM into the strut on the inner side of the curve, thus limiting roll. This happens in soft

mode. In hard mode, not only is the middle sphere closed, the ball is also imobilised in the middle of the cavity preventingall LHM flow through the module. Since this body roll limit now works irrespective of the spheres, it gave the designersmore freedom in choosing the spheres themselves. This might also be the reason for introducing 450 ccm spheres (theyare not used on non-Hydractive and Hydractive I cars).

The meaning of Sport and Normal (the new name for Comfort) modes have changed in Hydractive II. Switching to Sportdoes not mean sticking to hard mode any more. Hard and soft modes are normally used in both settings of the dashboardswitch, however, in Sport mode the system becomes more sensisitve and will sooner and more often switch to the hardsuspension.

The suspension is also fitted with an anti-sink valve that locks the system when the car is not running, using yet anothersphere. Its only purpose is to keep the car from sinking when not used, it does not influence the functioning of thesuspension system in any way. It must have been a marketing requirement to conceal yet another peculiarity of thehydropneumatic suspension system from the average driver.

The ECU used in Hydractive II is called H4.

Xantia Activa

This system never made it to the XM, so we only mention it for the sake of completeness. The aim of the Activa is toeliminate body roll completely. To this end, it uses yet another valve and an additional sphere, controlling two hydrauliccylinders located diagonally, one at the left front, the other at the right rear wheel.

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Fast sinking

New XMs have an anti-sink valve and reinforcement sphere. It takes a long time for them to sink visibly (certainly morethan a week when they are new). Older XMs with hydraulics in a good state will easily survive the night with minimumsink, that is without any load. The following assumes that the hydraulic system has been thoroughly cleaned using somesort of Hydraflush before further diagnostics:

If the back end sinks first (as it usually does), the prime suspect is the brake valve. The height corrector and rear struts areusually at the end of the checklist for this problem.

Usually once the brake valve is changed, things become better, but it's not uncommon then for the whole vehicle to sinkslowly, while the rear end sank in a matter of minutes before. The next element to check are the front struts. They arechecked for leakage by removing the rubber return hoses (and plugging up the metal conduit where they connect to theother returns or it will leak profusely), and depressurising the accumulator sphere but with a difference: leave the car atnormal drive height (without that you would need to wait too long for the car to sink even a little bit). The front should notsink appreciably within an hour (less than half an inch or so). Struts should be changed only if they sink very quickly(within minutes) or there is LHM obviously leaking from the exposed return (it should go extremely slowly, normally).Unfortunately, struts are quite expensive, and to my knowledge, unlike on the BX, they cannot be rebuilt.

If the car still sinks fast after this, and especially if it also produces a whistling sound at idle which stops when the steeringwheel is turned, the next element to look at is the flow distribution valve (usually close to the main accumulator, has fivehydraulic conduits running into it), and then the HP pump.

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Anti-sink system

The only purpose of the anti-sink system is to keep the car from lowering when not used, it does not interfere with thenormal functioning while in use. It attempts to minimize leaks inside the system by having only one element that can leak,the anti-sink valve itself.

There are two such valves, one for the front and one for the back. An additional anti-sink sphere (400 ccm, 50 bar, nodamping element) is located on the rear suspension beam on the left, next to the central sphere. This sphere only works onthe back, its main function being to maintain pressure for the rear brake to operate and to keep a reserve for the rear end incase weight is added to it with the engine off (such as loading the trunk). The reason for this setup is that the anti-sinkvalve has to decouple the rear brake feed because the brake valve is the most leaky element.

The anti-sink valves operate on the pressure differences in the system, without any electrical control. Under normalcircumstances, the two-piston section of the pump (all models fitted with anti-sink have a 6+2 piston pump, with no flowdistributor valve) supplies the pressure regulator and the main accumulator. The output from these two feed the whole

system with high pressure, going through the security valve which keeps the brake circuit constantly under pressure, forobvious reasons of security. If there is enough pressure in the system (which normally is), the security valve feeds the restof the suspension via the anti-sink valves and the height correctors.

When the car runs, the anti-sink valves are constantly open, and the suspension works exactly as in XMs not equippedwith this system. Even when the engine is switched off, the valves remain open as long as the feed from the accumulatorremains at a higher pressure than that of the suspension. They stay so even for some time afterwards. But as soon as theleakage in the struts, height regulators and the brake valve exhaust the pressure in the main accumulator (actually, as soonas the pressure drops below the suspension pressure, way before the security valve would close), the closing anti-sinkvalves isolate the suspension struts from the rest of the system. It is usually the front anti-sink valve that closes first as thefront of an unladen car is much heavier due to the engine and gearbox.

Besides, the rear anti-sink valve is connected slightly differently. As the rear brakes are fed from the rear suspensionpressure (making the rear brake force proportional to rear load, an age-old feature of hydraulic Citroëns, forming aninherent brake force distributor that conventional car manufacturers are reinventing these days), the rear anti-sink valvefeeds not only the brake circuit but the additional anti-sink sphere as well. Once the rear anti-sink valve closes, it cuts offthe brake valve and will rely on the additional sphere only.

The reason for all this is to counteract the internal leakage of the various suspension element which makes the LHM - andthe pressure - escape back to the reservoir. This leakage is not a failure generally, quite on the contrary, the system isdesigned this way. Components that are in constant motion, height correctors for instance, use this LM leaking past theirseals to lubricate themselves. Brake valves, on the other side, start to leak once they are worn. Consequently, the anti-sinkvalves isolate all the struts from the rest of the system to prevent any possible leakage to reduce the pressure in the struts,allowing the car to sink.

Compared to a non-anti-sink car, the leakage is quite drastically reduced indeed. With the suspension in prime condition astandard XM takes about 20-30 hours to sink completely, with the anti-sink system this would take about 10 days. Theanti-sink system itself, including the valves, is practically everlasting. The valves operate very seldom and as they do notneed any significant lubrication, they are manufactured with closer tolerances to prevent any leakage in them.

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Finding the current suspension mode

Failures in the Hydractive system (generally problems with sensors or their wiring) can force the suspension to be stuck inhard mode. To diagnose the fault, it would be convenient to know which mode the car is currently in. As H II systems use a1 kHz chopper to form the current operating the valves, this leads to an interesting way to learn the current status of thesuspension: this chopped current actually disturbs the radio reception. Tune your radio to a spot somewhere near 700 kHzwhere there is no incoming broadcast. When the solenoid valves are energized (that is, the suspension is in soft mode), youwill hear a characteristic buzzing sound from the radio. As you drive around, you can observe what triggers the hard modeerroneously.

On H I systems, you can connect a wire to the solenoid valve (it is located below the car, approximately beneath the frontseat). If you connect a simple multimeter to this wire, you'll be able to watch the 5-6 V driving the valve in soft mode.

Actually, in addition to diagnosing the suspension, this buzzing sound can also be used to decide which Hydractive systemyour car is fitted with. Alternatively, you can look for the ECU itself or the H II-only stiffness regulators.

ECU pinout

Pin 15N-1 Ignition switch feed (Fuse 19) 15N-2 not used 15N-3 Body movement sensor 15N-4 Body movement sensor 15N-5 Boot light switch 15N-6 Distance (speed) sensor 15N-7 Door opened switches 15N-8 Diagnostic socket

15N-9 Electrovalve 15N-10 Sport mode light on dashboard 15N-11 Unswitched feed, fuse 34 15N-12 not used 15N-13 Distance (speed) sensor 15N-14 Suspension switch 15N-15 Suspension switch 15B-1 not used 15B-2 Electrovalve 15B-3 Body movement sensor 15B-4 Body movement sensor 15B-5 not used 15B-6 Steering wheel sensor 15B-7 Brake pressure switch 15B-8 Ground 15B-9 Accelerator pedal potentiometer 15B-10 Accelerator pedal potentiometer 15B-11 Accelerator pedal potentiometer 15B-12 Steering wheel sensor 15B-13 Steering wheel sensor 15B-14 not used 15B-15 Steering wheel sensor

Bob HALL

Changing the LHM

Changing the LHM and rinsing the system is a part of normal service and care for all hydraulic Citroëns. Don't neglect thisif you want reliable and trouble-free operation from you car. Dirt in the system eventually wears out some of thecomponents if it's not dealt with in time. Although the system is extremely robust in itself, this does not mean that youshould tempt fate. If the flushing does not cure an eventual problem, then something has worn out and is not sealingproperly, so a lot of the flow of LHM goes from the high pressure parts straight back into the returns, which leaves less forits intended purpose.

Replacing the LHM (either with fresh LHM or Hydraurinçage, the hydraulic flushing fluid) is slightly more complicatedthan on previous Citroëns, due to the various spheres and valves.

First, you have to depressurize the system. Put the suspension in the lowest position, on steering assisted LHD cars turnthe steering wheel fully to the left (I suspect to the right on RHD, and I know RHD models are all fitted with DIRASS),this leaves the minimum amount of old LHM in the steering assist cylinder. After about two minutes with the enginerunning (do not open doors or tailgate or move the steering wheel during this time), loosen (do not remove!) the 12 mmbolt on the pressure regulator to empty the accumulator sphere, then turn off the engine.

It is of vital importance to observe the procedure to depressurize the system carefully. You can get the H I system stuck inhard mode if you, by error, remove the main accumulator pressure while the middle sphere is closed. When you firstpressurize the car again and the system switches to hard for any reason (what can be triggered by simply opening a door),the car will move forcefully, potentially rupturing a sphere membrane. Whether it will jump or drop depends on the actualresidual pressure of the middle sphere compared to the pressure in the struts. In either way, when the computer opens thissphere in the course of its self-diagnostics, the resulting jump or drop can be brutal enough to knock out supports or causeother serious damage. This is very dangerous.

Empty the LHM reservoir. The easiest way is to remove the refill cap, and to syphon out the fluid using a long tube. Then,remove the reservoir; this is done by removing one bolt, pulling out a safety pin, and taking off the uptake-return assemblyholder (the big clip that holds the plastic with all the tubes coming to it). Have a completely air-tight nylon bag and somerags handy. Pull the whole container towards the front carefully, then tilt its front end upwards (it will be easier if you

remove the uptake-return assembly first). As soon as you can, put the bag under and around the reservoir because therewill be some LHM spilled.

Clean the reservoir thoroughly. Start with diesel fuel, then some gasoline, and finally detergent and water to get all thegrime out. It is not very easy because the reservoir has a built-in labyrinth to prevent the LHM splashing around inside.The bottom of the container has special indentations designed to trap the crud (easily seen through the opening), be sureto clean them out thoroughly-using a hard bristle brush is a good idea.

By this time the uptake-return assembly will be drained into the bag, so you may dispose of it, but still keep the ragsunderneath. At this point you need to remove the uptake and return filters. The return is clearly visible, it's milkyyelow-white plastic, about 4" deep and with a slightly oval cross-section. It is held by a small hook on one side, where ittouches the rest of the assembly. The uptake filter is a long cone made of the same kind of plastic, hiding in the plasticextension of the uptake tube (the thickest one on the assembly) that goes into the LHM container. You can take it out byslightly twisting and pulling it out of its tube.

Clean the filters using clean gasoline. Dry out the container and the filters thoroughly with compressed air, thenreassemble everything back to the reservoir, and the reservoir back into the car. Pour new fluid into the reservoir until thegauge rises to the top position, do not overfill!

You may need to prime the pump by removing the uptake hose and pouring some LHM into the pump, or even sucking onthe hose to get the LHM flowing-use some kind of a vacuum pump, LHM tastes awful...

On cars with conventional steering, start the engine, then try to move the steering wheel. When you feel it is working asit should, the pump has started pumping. A few short races of the engine can cure the stubborn cases. If it does notco-operate, you will need to prime the pump again. Turn the steering wheel each way fully until the steering works withoutglitches, it usually takes one or two full turns from lock to lock. On cars with DIRAVI steering, I suspect that-unlikeCX/SM-it does not need to be catered for speciffically, because it is very low in the system so it's unlikely that air pocketswould form. It should be enough not to move the wheel while the system is depressurised and without fluid (like in themiddle of a fluid change), and then do a full turn left-right-left-right with the steering wheel once the pressure is back up.

Tighten the bolt on the pressure regulator. As you are doing this, you will hear the LHM filling the accumulator sphere,followed by the usual click of the regulator as it disengages. If you don't, you might have to do another short race of theengine, there might be an air pocket in the regulator or the pump. In any case, if the regulator clicked, the STOP lampshould have gone out.

Rise the suspension slowly. It is entirely possible that it will light the STOP lamp a few times as you do that as the airpockets clear out. Check the LHM level and replenish as needed, do not let it go below minimum. Keep rising thesuspension until you get to the top position, then lower the suspension to the bottom position, and repeat the procedure.This time you should get no STOPs. When you have reached the top position again, you can lower the suspension to itsnormal operating position, or if you want, you can cycle it once again just to be sure.

At this point you should bleed the brake valve and the ABS block. These are the additional bleed points, but I have foundthey rarely need bleeding unless the system has been emptied of LHM by these particular parts being dissasembled. Youcan help matters by doing a small ABS test on a safe part of the road before bleeding out the brakes (careful, they mightnot react the way you are used to!). Bleeding the brakes will then take care of the remaining air bubbles. The brake valve isbelow the LHM container, its bleed screw is on the bottom side, it usually has a small green plastic washer on it-it isdefinitely difficult to get at. The ABS block is located on the left front wing, beneath the battery and behind the radiator.Not all types have a bleed screw.

You can bleed the front brakes without removing the wheels (but it will be simpler if you do remove them), at the rear youhave remove the wheels to get to the bleed screw. Use a hexagonal socket that fits on the bleeding screw (don't try it withsimple spanners. they would most certainly destroy the bleeder screw or even snap it off), a little can, a piece of transparentplastic tube about a foot long with 4 mm inner diameter. Also prepare something to put on the brake pad to keep it presseddown lightly, a piece of brick or similar. You might also need a small hammer, preferably brass, or a steel hammer and apiece of brass.

Put the car on level surface and suspension in the uppermost position, and the parking brake on just slightly, enough tokeep the car from moving. Keep the engine running. Turn the steering wheel fully to one side to expose the bleed screw onthe other side. There is a small rubber cap over the bleed screw. Loosen the screw with the socket until it just starts

flowing. If the screw is stuck, don't force it, tap it gently with the small hammer. Attach the tube onto the top of the bleedscrew, and put the other end into the can. Put the brick or whatever other weight you have onto the brake pad. Using astandard wrench of the same size, loosen the bleed screw and watch the fluid coming out through the hose. Keep it goinguntil clear fluid with no discoloration and bubbles comes through. Then repeat the whole procedure for the wheel on theother side.

At the rear end, remove both wheels. Remembering to keep the car on park brake. Once you have taken off the wheels,return the suspension to the uppermost position. For the front wheels this only simplifies access, but for the rear one it isessential-the car uses the rear suspension pressure for braking on the rear wheels. The only way to have pressure in therear suspension without the wheels supporting the weight of the car is to have the suspension in the top position. Theprocedure is similar to the front wheels: while the engine is running, loosen the bleed screw (the back ones are particularlyprone to getting stuck, be careful), attach the hose, put weight on brake pad, bleed until clar fluid flows out of the bleeder.For the back brakes it usually takes a little longer than for the front ones.

Air bubbles in the rear brake lines are often responsible for strange braking effects on uneven surfaces, like sudden shortfailure of back brake to work after you hit a bump while braking (resulting in the rear jumping up). Also, the rearsuspension comfort can be compromised by air in the lines because it makes the volume of the fluid in them compress-ofcourse, it's the air compressing really.

The procedure is exactly the same for Hydraurinçage. The only differences are: it stays in the system for a shorter time,and it has a different color which helps a lot when bleeding. With the rinsing fluid in the system, it is advisable to clean thefilters about each 500 km, so you get rid of all the crud the fluid dissolves. You need to remove the LHM container in orderto get to the filters, the labyrinth in it will help with tilting it without spilling out the fluid, but be prepared for a mess (usenylon bag and lots of rags). However, it is well worth the effort-by the second or third 500 km period the filters should bealmost clean, indicating that the system has indeed been rinsed out.

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Power steering

The XM came equipped with one of two possible power steering systems. The conventional one is practically equivalent to

the BX one, with sizes of cylinders adjusted for proper assistance force. This is called DIRASS from the French DirectionAsistée. The other is the self-centering, speed sensitive, fully amplified system to be found on the SM and the CX as well,called DIRAVI (Direction Appel Rasservi) or, sometimes, Varipower. This system is completely different from theconventional one, even the supporting hydraulic components are different. Its peculiarity is that it automatically centersthe steering even if the car is standing still, and is less servo assisted at higher speeds and tighter curves.

Diravi was only fitted to 3.0 liter models and it never came in RHD.

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Noise from the front

There are several possible causes. The connecting rod ball joints might be worn (there are two of them for each rod, theyconnect the strut to the anti-roll bar). There are two types of rods, adjustable and fixed length; the replacement rods willusually be fixed. If you find an adjustable one on your car, replace both of them.

The steering rod ball joints might be worn.

Check the wishbone rubber mounts. These are nasty because you start to think of them only when they begin to creak,but this is way too late. Long before that they will cause bad wheel geometry and rapid tire wear, not to mmention a strangelimited understeering tendency and in later stages (when they do start rattling), rather uncomfortable drive.

The bottom ball joint, although it is quite rare, can be worn, too.

Check the strut cup, the top part that attaches the strut and sphere holder to the body. This is made out of twohemispherical stamped parts joined by vulcanised rubber. The first one to go is usually the one on the passenger side-that'swhere the outer edge of the road is, together with the majority of potholes. Some very early XMs were known to punch thestrut through the hood when this failed, but the construction was changed early on to prevent that. It becomes very noisyon holes and it's easy to diagnose because you can easily move the whole wheel up and down a fraction of an inch andobserve the sphere and support doing the same. These will fail in record time if the strut spheres are bad.

It might be the strut itself. In advanced wear (or rust) stages the pushrod has enough wear to rattle inside the remnants of

its bearing. Also easily checked by holding onto the strut and trying to shake it vigorously-a clicking sound can be heard. Ifthe car also has the tendency to suddenly drop its front end to the ground for no apparent reason (even if it does climb backup), and the height corrector is OK, replace the strut. Keep in mind that when a strut fails, the LHM will become socontaminated with metal debris that you will be lucky if you only get away with flushing and an LHM change; in most cases,however, you will need to remove and refurbish the accumulator-regulator assembly, the flow distribution valve, and oftenthe brake valve and the security valve as well.

The wear on these parts is excessive if the corresponding sphere becomes flat. Failure of the bottom ball joints or thesteering rod joints is dangerous for obvious reasons and are always checked at MOT (or the equivalent in your country),besides, the manufacturers take great care to insure that they don't fail. On the other hand, wishbone silent-blocs, strutsupports and connecting rod ball joints are horses of a different color. If the first two are shot, the steering becomes mushyand the car tends to steer itself on bumpy or sloping roads. In addition, this places undue strain on the steering rods andrack, as this becomes the only true rigid element keeping the suspension in its right place. Shot wishbone supports makethe situation worse for strut supports and the other way around. Having this checked early on will save you the added(much larger) expense of strut changes and servicing the steering rack.

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Front struts

The strut can suffer due to various reasons: hard suspension due to flat spheres, failing strut or wishbone mounts, old ordirty LHM, or simply due to normal wear. Any problem, as usual, aggravates the normal wear several times.

Unlike the BX struts, XM ones are not (easily) renewable. They usually have to be replaced, and a flush of the hydraulicsystem has to be done at the very least. A defective strut is usually diagnosed by it leaking into the return excessively, aswell as having free-play when agitated (a click can be heard). Defective struts must be replaced as soon as possible becausethe debris resulting from the wear-out wreaks havoc with the rest of the hydraulics.

Since a certain amount of water and debris, as well as air bubbles in the LHM are normal due to use and wear of the system,a simple operation goes a long way in preventing problems: traveling the suspension fully up, fully down, fully up, and back

to normal height again regulairly, say, once in a week or two. Also, the LHM filters should be cleaned regulairly at least, ifyou are short of cash or for any other reson prevented from doing a flush and LHM change at the prescribed intervals.

The strut mounts can also cause problems on very early Series 1 XMs. If cracks develop in the vulcanised rubber partconnecting the inner and outer parts of the strut, they can separate completely. As a result, the strut will be driven throughthe hood, puncturing or indenting it rather nastily. This setup was modified very early; later variants, although the rubbercan fail, will not let the strut pop out of the hood; however, the steering will become very imprecise and noisy. If you drivethe car in this comdition for a longer period, this will damage the struts themselves, as well as the steering rack, rod andvalve.

The danger is somewhat more imminent on the passenger side as that is closer to the edge of the road where most of thepotholes are.

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Trailing arm bearings

All Citroëns and Peugeots with trailing arm suspension suffer from these problems, although it appears more often onCitroëns, probably due to deflated rear spheres increasing wear on the bearing immensely. The basic problem is that thebearings are not greased adequately. Some people modify the trailing arm by adding a grease nipple (many CX owners dothis). However, the first and foremost precaution is having a properly operating rear suspension.

The XM's arms are much more susceptible to extreme wear problems (such as bearing outer rings being completely wornthrough) because they are made out of aluminum, in contrast to the cast iron arms of the BX. There is a bearingreplacement kit but you won't need it generally: the bolt hardly ever gets worn completely, and the bearings and seals areindustry standard and readily available from the original manufacturer (bearings are usually made by Timken). The armswill start creaking and getting stuck well before the needles actually get crushed. If you can hear strange noises from therear end as it rises or lowers, or the rear end remains hard in a bounce test even with brand new spheres, check thebearings. Extreme cases are very easy to spot because the top end of the rear wheels slopes inwards (just put the suspensionin high, go back some twenty meters behind the car and observe the wheels).

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Steering rack

Steering rack failures are generally caused by problems in the front suspension.

If you can hear clicking noises from the left side of the rack (LHD), the bottom pinion bearing will fail. You can test forthis by agitating the steering rod when the steering wheel is turned fully to the right. The bearing is quite hard to change (ifpossible at all) without removing the rack, and also very hard to get as a spare part. It is a rather small needle bearing. Thetpp bearing of the pinion could also be at fault but this is rather rare, unless the steering assist valve leaks. Then the leakingLHM could wash out the grease from the bearing. It is possible to renew this bearing, as well as the sealing rings and thevalve itself without pulling out the whole rack, but it is difficult because it's not easy to get at (LHM reservoir and frontmiddle sphere have to be removed, also be prepared to do yoga in order to get a wrench where it's needed).

If the rattle comes from the other side, then it's the synther bearing. It can actually be replaced without removing thewhole rack, but you do have to pull out the steering valve assembly at least half way to free the steering rod in the rack andpull it out.

Removing the steering rod is a rather complicated task. Note that the following description applies to LHD cars equippedwith DIRASS (conventional power steering) only. As far as I know, removing the DIRAVI steering assembly is notpossible without removing the engine, too.

First, depressurise the hydraulic system. Turn the steering wheel fully to the left. Remove the LHM reservoir. If you havea hydractive model, remove the front middle sphere. Then uncouple the link rods and the hydraulic conduits of thesteering valve.

Undo the large hex nut holding the tensioner, remove the spring, and if you can, the piston-like part that presses into thesteering rod. Remove the steering shaft by unscrewing the rubber joint, then pushing the shaft towards the steering wheel.Loosen the but and bolt holding the steering assist cylinder on the rack but do not remove the cylinder yet. After youhave losened the whole rack, you may remove the bolts completely.

Pull out the heat shield. Dismantle the hydraulic assistance cylinder. Be careful, there will be a fair amount of LHM still

inside, do not extend the piston rod until you have rags or a can on the end of the cylicder where the conduits go, thendrain all the fluid by pulling and pushing the rod all the way in and out.

Unscrew and remove the steering valve carefully, you may need either to turn the pinion or to move the rod to accomplishthis. Now the whole steering rack can be pulled out to the right. Remember not to remove the leak return hose from thefront height corrector.

The rack can be now dissasembled by unscrewing the ball joint from the side closer to the steering valve. After that theshaft can be pulled out through the synther bearing on the other side. It has to be dissasembled to this stage if you want togain access to the bottom bearing. Assembly is in the reverse order taking care to do some work to block the opening inthe rack where the steering valve assembly will go, as well as the hydraulic conduits, so that dirt cannot get into the rackand the valve. Plenty of grease will also be needed. Be sure to replace all torn or worn boots. Plan on the better part of a dayto do all the work...

All steering rack parts except the valve seals and rings appear on the parts microfiches, thus, can be ordered.

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Steering valve

The steering valve can be renewed but it is a rather difficult job. First of all, be careful with second hand units: the only realway to check them would be to open them, but once you do, you have to change the seals anyway, because the old ones willnever seal again. These rings are made of a black, teflon-like plastic. There is a Citroën kit for renewing a steering valve,containing three new rings, two sealing rings (simmering), a replacement rubber seal for the HP supply hydraulic conduitand a new plastic cap for the top of the steering valve (just under where the steering attaches). It may however be a goodidea to go to a scrap yard and get a valve, rebuild it and have it ready to be put in instead of the old one. It will save sometime.

The whole operation takes almost half a day because it's so difficult to get at the parts. You want to avoid this job unless it'sabsolutely necessary. There is a relatively simple way to test that it's actually the steering valve that causes most of theleakage: use an old brake valve bleed screw (usually found on brake valves for CX and BX) to close the main high pressure

supply from the pressure accumulator and regulator assembly-this is the smallest diameter hydraulic pipe on the unit.Take this out (including the rubber seal) and screw in the bleed screw istead; it should be an exact fit. This will make theLHM only go through the steering part of the system, the main accumulator will just reach operating pressure and click asusual, and should remain charged since you have put all of its LHM-consumers off-line. Note that the STOP lamp will notgo out because the pressure switch is also off-line.

If both the pump and the flow regulator are OK, and you still get a whistling sound, the steering valve is worn.Incidentally, this is also a good way to test the main pressure regulator for leakage-with this bleed screw in place, thepressure in the main accumulator should remain there for a very long time (possibly even days).

After the test, you must depressurise the regulator before removing the bleed screw, remember, that's where the LHMwould normally come out to be used by the suspension and brakes!

Removing the valve is real pain in the neck. You will have to remove the driver's side wheel, the LHM reservoir and themiddle sphere, just to be able to get at it.

You need to uncouple the steering wheel (unscrew the rubber damper from the valve assembly, you will probably have toleave half of the rubber damper plate assembly on the valve itself because of limited space) and push it upwards. Thesteering shaft itself is actually made of two coaxial shafts that allow for shaft compression in a crash. This effect will giveyou just enough space to be able to remove the valve later.

Before you loosen the two hex wrench bolts that hold the valve on the steering rack, you will need another huge hexwrench (22 mm I think) and unscrew the tensioner in the steering rack. Careful, there is a spring in there. To get to it youhave to remove the middle sphere. Once this is done you can unscrew the hydraulics off the valve, then loosen the two hexscrews that hold it onto the rack, and then pull the valve assembly upwards and out. You will need to turn it slightly to get itout.

When you have the valve out of there, the first thing you'll need to do is pop out the two sealing rings. Removing the circlipmakes it possible to push out the rotor of the valve together with the main bearing. Once you have done that, the rings aredead, you must replace them. You will also notice that the main HP supply goes into the stator part of the valve through an

adapter nut. This is because the valve is Bendix and the hydraulics up to that point are Citroën: the pipes have completelydifferent endings. Unscrew the adapter nut carefully, you will find a simple one-way valve mechanism under it that needsto be cleaned. There is also a one-way valve of similar nature in the return pipe. Before replacing the rings themselves,clean the old grease out of the main bearing carefully and verify that the bearing runs smoothly.

When you have done all this, you will need to change the main valve rings. Do not remove all the old ones, there are onlythree rings while there is room for four. If you look inside the stator part, you will clearly see where the old ringswere-there will be three very smooth bands on the inner wall. You will also notice that the bottom ring that is missingserves no apparent purpose-in fact, this is the outer seal that prevents leakage of the LHM towards the main bearing. Thepoint is, you will see that instead of replacing the bottom ring, you can add the new ring to the free groove. If you look atthe rotor and stator you'll find that they both serve the same function. This way the new ring will not go over the smoothedout part of the stator, and will also have the old ring as backup. The other two rings need to be replaced, so cut them out.

The way you change the rings is very tricky. I actually used a piece of an old fizzy tablet can (calcium tablets as I recall)because it fitted the diameter exactly, and was made of very thin aluminum alloy so it didn't add much to the diameter. It'sa 18 cm long tube of about 2.5 cm in diameter. Using a conical tool I first stretched the rings (very) slowly, then pluggedthe thinner end into the aluminum tube and transferred the rings from the conus to the tube, all three of them. Then youput the rotor part into the tube, and slowly, one by one, slide the rings off until they pop into place. Be very careful to get itin one go! When you have done this, leave the rings for about 2-3 hours, they will shrink back, although not completely.

The whole assembly is put back together in the opposite way. You have to be very careful as the rings on the rotor go backinto the stator part one by one, not to knick them. A 45 degree conical angle is provided on the edge they will be goingover, which makes things a bit easier. Before you start, use a bit of fresh LHM to lubricate the rings and the inside of thestator. It may still need a few taps with a plastic or rubber hammer to get them in. You will notice that the rotor will nowturn with a lot more resistance. The resistance should be uniform. Go on with the sealing rings, and a liberal amount ofgrease for the main bearing. Then the whole thing goes back into the steering rack (apply a liberal amount of grease to

cogwheel. Then tighten the valve mechanism back into the rack, connect the hydraulics, tighten the tensioner andreconnect the steering wheel. Finally, if you have loosened it, secure the rack.

The hydraulic conduits from the steering valve to the steering assistance hydraulic cylinder seal using large conical seats.Unlike Citroën hydraulics in general, these need to be very tight to seal as intended, and you have to be very careful not todrive any dirt into the seats. The way I did it was to tape over the seats on the steering valve, then took off the tape whenthe valve was already in place.

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