C5 Suspension Shenanigans

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Mdqagd
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C5 Suspension Shenanigans

Post by Mdqagd »

Just bought 2002 C5 2.2 HDI Estate, 75000 miles, from the auction. Dipping my toe into Citroen ownership for the first time. Excited but afraid. I know Im going to have to do some work on my floating on fluid bargain.

Rear suspension sometimes sinks when parked up, sometimes doesn't. After sinking it corrects itself on unlocking. The pump pumps for 15 seconds, then a the sound of rushing fluid, then it jumps up with a bang, then rises majestically to ride height.

When driving along and enjoying the smooth ride, the back end will intermittently rise quickly every ten minutes or so, and then gradually falls back.

LDS fluid level a bit low. No obvious leaks around the struts.

Give me somewhere to start chaps, I really want to like my new French friend.
cachaciero
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Post by cachaciero »

Rear height corrector, these are electrical potentiometers and the track / wiper gets worn and noisy with age, a not uncommon problem and not difficult or expensive to replace.
You don't say what trim level, the Exclusive has a couple of extra bits on the suspension although it is unlikely these would cause the problem you describe.

cachaciero
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Mdqagd
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Post by Mdqagd »

Thanks for the speedy reply, Ill get it changed. Its an SX.
wheeler
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Post by wheeler »

I'd say rear sinking overnight is more likley to be (internally) leaking rear strut(s).
The body height sensors do cause problems but not usually sinking like this + they normally flag up the 'SERIOUS SUSPENSION FAULT' warning on the dash display when they go faulty. If you want to rule them out anyway you could swap the front one with the back one as they are both the same & see if the fault changes to the front ?
cachaciero
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Post by cachaciero »

wheeler wrote:I'd say rear sinking overnight is more likley to be (internally) leaking rear strut(s).
The body height sensors do cause problems but not usually sinking like this + they normally flag up the 'SERIOUS SUSPENSION FAULT' warning on the dash display when they go faulty. If you want to rule them out anyway you could swap the front one with the back one as they are both the same & see if the fault changes to the front ?
Well I wouldn't go against wheelers knowledge and experience ,a quick swap of the sensors is a quick way of elimination if a Lexia is not available. However it is my impression that I have seen more reports of confirmed failed sensors than strut leakage.

Looking on the really black side it could be a leaking valve in the BHI.

That's set me on a whole new train of thought :-) If it is leakage around the strut then the only place the oil can go is back through the gaiter drain which is not really capable of large oil flows.
So if overnight there is leakage around the strut piston i.e from the high pressure sphere side to the low pressure side the gaiter on the leaking strut would fill with oil and given that the two struts are common effectively two struts worth. Then once the BHI runs to re-pressurise the strut and raise the car the oil in the gaiter would itself become pressurised and my gut feel is that to such an extent that it would blow th return pipe of or split something but any which way dump some oil on the floor.

Right or wrong it would be worth feeling the gaiters after an overnight rest before opening the car (or leave battery disconnected) to see if one or the other is full of oil if so it would prove the strut leakage theory.

cachaciero
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wheeler
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Post by wheeler »

cachaciero wrote: However it is my impression that I have seen more reports of confirmed failed sensors than strut leakage.

Looking on the really black side it could be a leaking valve in the BHI.
The body height sensors do fail quite commonly but id say 90% of the time they bring up the suspension fault message on the display & i cant think if i've seen any causing an overnight sinking fault. Yes the BHI could also cause this fault if you are really unlucky but i've yet to see a BHI fail in this way.
Ideally you need a 4 post ramp or a pit to check the struts but the way to do it is leave the supension set at normal height & pull off the leak off pipe (not the breather that goes into the rear beam) & leave overnight, you should'nt really get any LDS leaking out, the one thats trickling out fluid will be the faulty one. The amount that leaks out will not be alot. Done plenty of them for this fault.
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Post by cachaciero »

wheeler wrote: Ideally you need a 4 post ramp or a pit to check the struts ........
and much else besides, I wish had these at my disposal:-)

Looking back at the OP I think that the thing that made be go for the correctors was the fact that the sinkage isn't consistent i.e doesn't do it every night and the fact that the back sporadically rises up and then settles while driving. Can't say I've ever heard the sound of rushing fluid or rising of the stops with a "bang". I mean the flow rate from the pump is not high enough to be audible, 15 seconds sound about right to get it moving of the bump stop.
Hopefully Mdgagd will tell us what it was when he fixes it :-)

cachaciero
2006 Toyota Prius T Spirit
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1996 XM 2.1 TD Auto VSX
1995 XM 2.1 TD Auto SX died @ 140K
1987 CX 2.5 Gti Turbo II dead
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1981 CX 2.4 Pallas Auto
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Mdqagd
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Post by Mdqagd »

Well my citro-phile friends, I cant say how grateful I am for your interest.

I switched the correctors with no change.

Interestingly I removed the return pipes as you suggested and a small amount of fluid squirted out under pressure, then a lot of air hissed out under pressure. This happens on both sides, but only on the one you take off first, so I assume the return pipes join on their way back, and that the pipe is blocked.

Leaving the pipes off overnight discharges some fluid on both sides, I will repeat with containers to see how much. I perhaps need to renew the seals on both sides.

When under in my pit (or was it the four poster lift) I found evidence of a fluid leak in the region of the offside front subframe. On closer inspection there are three pipes which rise up into a sleeve and re appear from the sleeve under the bonnet. The pipes are dry at the top under the bonnet, but damp at the bottom end of the sleeve. Could this leak be coming from the return pipe blockage?

I wish I could describe the fluid sound and bang better... With the back end sunk the pump comes on but the back end doesn't rise at all. The rushing of fluid (or could there be some air?) noise comes and the back end still doesn't rise until you get the bang when whatever is stopping the car rising is overcome.

Thanks again for your interest - enjoying the diagnostic challenge!!
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Post by cachaciero »

I wonder if the "bang" is not related to the problem per se but is just a result of the change in forces / loads as the strut takes control, thinking shot arm bearings here.

I would expect a small amount of fluid to get past the seals and into the gaiter as part of normal lubrification.
I am puzzled about air rushing out. Air in the system could cause problems have you tried bleeding the system, might be worth doing a few cycles of max low max hi and seeing if there is any improvment but note max low is not max mechanical low so you cannot guarantee to get all air out of the system doing this .

cachaciero
2006 Toyota Prius T Spirit
2001 2.2 C5 Exclusive SE
1996 XM 2.1 TD Auto VSX
1995 XM 2.1 TD Auto SX died @ 140K
1987 CX 2.5 Gti Turbo II dead
1984 Ford Scorpio
1981 CX 2.4 Pallas Auto
Renault 21
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viorelovidiu
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Post by viorelovidiu »

well, I have exactly the same problem since I bought my car C5 II 2.0i SX last year on front side. At first I`ve replaced entire BHI unit (new unit) and the sinking was still present, after that I`ve replaced front sensor (got better a bit but still was sinking, no going up/down very fast while cornering), and at last I`ve replaced both front telescopes from another car and the sinking phenomena has been reduced a bit.

When parked with or without battery disconnected the car will sink after 5-7 hours :shock: and the most interesting part: I unlock it and after raising up to the ride height and locking it again, the car will stay at the same height even for a week! :shock: (I`ve checked this twice!)

When the car sinks, it sinks equally on both side but not so low like before... and pump works about 5-7 seconds to get the correct ride height. I think I get used with this...

I checked with bottles the amount of fluid from the return pipes overnight and I`ve got around 10-15mililiters per wheel.

I`m confused about gaiters, can someone point those parts in a picture? I dont know how to check them if there is a leakage.

Thanks!
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Mdqagd
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Post by Mdqagd »

buna prietena mea

As you describe, the car can sink in just a couple of hours, but if I open the door and bring her back to height she wont sink again.
viorelovidiu
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Post by viorelovidiu »

Mdqagd wrote:buna prietena mea

As you describe, the car can sink in just a couple of hours, but if I open the door and bring her back to height she wont sink again.
do you mean "buna prietenul meu" I`m a boy not a girl :P


Hopefully you`ll find a solution and share it with us :)
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Mdqagd
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Post by Mdqagd »

I think I am getting closer.

When I unlock the car, pump comes on, builds up pressure, after 30 secs the rear jumps with a "bang", car then finds correct height. You can then raise and lower the car smoothly without any jumps or bangs. Drive very gently around the block and it still rises and falls smoothly. Drive aggressively around the block, then try to raise the car and you get the same build up of pressure and the rear jumps with a bang.

It therefore seems (to me) that when the regulator switches from soft to hard mode the valve is getting stuck. The pump is then having to push really hard to overcome this to get back into soft mode. This must be happening as I am driving along, which would explain why the car is jumping randomly. Does this sound plausible?

Its jolly cold in Scotland.
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Post by mooseshaver »

Could it be rear brakes binding? My previous C5 would sometimes not raise at the rear in the morning, and there would be a small thud and the thing would shoot up.
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Post by Julz »

mooseshaver wrote:Could it be rear brakes binding? My previous C5 would sometimes not raise at the rear in the morning, and there would be a small thud and the thing would shoot up.
mine did that at the rear the other day having been parked up for a few days in all that wet weather we had, hoped it was just the rear brakes siezing
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