suspension

[bennyboy]

general question on suspension,,on 95 m reg xm 2.0 turbo
when car is parked on drive i have noticed that the rear suspension sinks first (totally sunk after about 4--5 hours although the front can take 8 hours plus to lower,,
is this normal (i use the term "normal " loosely when talking about a citroen..)
i just thought that they would sink at the same rate or the front first with it being heavier
i am a citroen newbie trying hard to understand french cars
(my boss is french and i cannot understand his way of thinking) maybe i am just not european enough

[Peter.N.]

As you suggest, there is no such thing as normal with a hydropnumatic system. I have four XMs and they all behave differently, it depends largely on the condition of the various moving parts of the system. If they work OK, I leave them alone.

[CitroJim]

i am a citroen newbie trying hard to understand french cars

Benny, ther is no understanding French cars! Part of their charm

I assue an M plate XM would have anti-sink but that does not mean it cannot and will not sink. Generally the rear sinks first because there is less pressure knocking around the rear to begin with and secondly, more places for it to leak away, the brake dosuer for one. The front has more pressure and this tends to snap the anti-sink valves shut faster and more reliably.

As Peter says, if it all works well enough, than best to leave it be. Chasing issues like this can be a bit like chasing rainbows and all for a car that might eventually stay up a bit longer.

As a newbie (we were all there once) the very best bet is to get to know a local who knows hydraulic Citroens well and allow said person to look over the car and teach you all about them. I'll bet there is such a person somewhere local and maybe even a member of this forum.

The first thing to do on any hydraulic Citroen is to time the interval between ticks from the pressure regulator. They should occur no more frequently than every 30s at idle in a healthy system but only start to worry if they occur at less then 10s intervals. A short tick interval suggests a flat accumulator sphere or higher than normal internal leakage somewhere in the system.

[citronut]

Benny wrote
" (i use the term "normal " loosely when talking about a citroen..)"

they are normal its all the others that arnt

regards malcolm

[bennyboy]

thank you all for replying,,
the answers brought up another question
the pressure regulator ticks about every 30 seconds but as it is pressurising itself it squeels fairly loud,,sounds like a slipping belt but it is not,,the only way to stop it squealing is to turn the steering wheel,,even a quarter inch is enough to stop it ,always does it at idle,,hot or cold but very rarely when driving as you are usually moving steering wheel even slightly on the straight
does anyone have any clues as to why it would be doing this,,the sqeal is driving me crazy..
lhm level is spot on
it is green in colour but could it be thin therefore not vacuuming enough or is pump maybe needing replaced clutching at straws here
the pump belt is fine,have tried slackening and tightening it ..noise definately from the pump
does anyone have a remedy to this problem

[Sid_the_Squid]

Have you checked the crank pulley which drives the aux belt, if its one of those with a rubber bit in the middle it may be perished causing the crank pulley to slip against itself when under load.

[FrenchLeave]

With regard to your original question, it's easy to check if your car has antisink without getting underneath it. Lift the bonnet, if your hydraulic pump has only one pressure outlet then you don't have antisink. If it has two pressure lines then it's the newer 6+2 pump with only two pistons supplying the suspension and it will have antisink.

Without antisink there are lots of potential leakage points - the brake doseur and height control valve being obvious and major items.

With antisink all the major leakage points are taken out of the equation and you are limited to the suspension units themselves plus the hydractive valve. Leakage from the antisink valve is almost unheard of.

I would agree with previous advice that if the sinking is very slow then leave well alone, but if it becomes bothersome then my suspicion would be one of the suspension units. Once again, relatively easy to check; with the back up on ramps and the engine running, pull off the return line from each unit in turn. Any more than the occasional drop of fluid and you've found your problem.

Derek

[citronut]

these orible multi rib belts do need to be excesivly tight, you might think its tight/to tight, but just adjust it a little more,

there is a lot of torque required to turn the pump, as it it pumping 2600 psi,

i feel they just dont grip like the old V belts did,

regards malcolm

[bennyboy]

thank you citronut ,,,my pump has only 2 pipws attached to it...i take it supply and return..so that must mean mine is the older pump which has a v belt ot a ribbed one ,,,,does that seem about right,,,
need to get this sorted as the squeal is getting to me

[aerodynamica]

Hi there, yes, best to determine if your Xm has the anti sink arrangement as being an M reg. it could be either. The Xantia gained anti sink almost exclusively from M reg. onwards but I think the Xm still had the old sinking system for a slightly longer time.

Anyway if it is a 'sinking' type (that is, a PROPER Citroen) then the sinking is all normal and good. In fact an Xm that stays up for 4-8 hours is good news!

does anyone have any clues as to why it would be doing this,,the sqeal is driving me crazy..

-This however, I wonder. If it's a 'sinking' XM then it will be of the type that emits a surprisingly loud hiss noise on occasion that will stop when the steering wheel is moved. It is only the sinking ones that do this as they have a device called a Flow Divider Valve to operated the power assisted steering. This valve makes a loud hiss noise that might be mistaken for a 'slipping belt noise' ?

PAS BXs, and pre anti sink Xantias also have the FDV valve and make the hiss noise but it's not as loud as on the Xm..

Need to know the sink or non-sink of your car first!

[aerodynamica]

thank you citronut ,,,my pump has only 2 pipes attached to it...i take it supply and return..so that must mean mine is the older pump which has a v belt ot a ribbed one ,,,,does that seem about right,,,
need to get this sorted as the squeal is getting to me

- Right then, if it's an inlet-outlet pump then it's a 'sinker' and hence, has an FDV valve for the power steering. These cars make a loud hiss-screech noise that is, I'm sorry to say totally normal and healthy. If they don't do this in fact, the FDV or PAS pinion valve (or pump) is duff.

What's your thoughts on that?

[bennyboy]

sorry to hear the noise is normal i would not say it is a hiss it sounds an old fan belt squealing after you went through a deep puddle

[citronut]

i dont recall the XM ever having a V belt as i think it is to new, you tell the differance by the type of pully, if it has a flat surface with maybe 6 groves it is the orible multi groove belt, the V belt type has a V shaped pully surface

regards malcolm

[aerodynamica]

Having said that, the hiss noise as audible as it is, shouldn't be as high pitched as a squealing belt so perhaps there is a different problem on yours. AFAIK, when the hiss noise goes off, the HP pump is under load feeding both the PAS and the pressure regulator at the same time (still not 100% on the FDV valve's behavior tho) so perhaps the HP belt is slipping during this time. Also check the HP pump itself for duff bearings as these could be squealing like a bitch.

Bring the Xm to the CCC rally tomorrow (Sunday the 19th) at Wood green animal shelter and let us diagnose it for you!

[bennyboy]

not had a chance to take pump off yet to check bearing..but i can say it is definately a 2 pipe pump and a V belt..i am now wondering if someone has changed the pump or i just have the last of the v belt model

i have just logged in after working and did not know about the rally at the animal shelter or i would have come along