Hi, we have an XM25TD Est. that is very slow on the rear end rising in the morning and will sometimes, when idling, just drop to the ground and then slowly rise. Also the hydraulic light will come on when steering and braking. When connested to a scanner it said fault with rear hydraulic sleuce?
Any help would be much appreciated.
Cheers
PS - Hydraulic pump and regulator have been checked.

Feeling around in the dark at the moment but I might suggest that you remove the inlet pipe to the LHM pump amd top up the pump at that point before replacing the pipe and starting the engine. I seem to remember you can get air in the system giving the effect you are experiencing. The rear brakes should also be bled to see if there is air in that area. Bleed a considerable amount out into a jar to be sure you have driven all the air out of the rear pipes. Save the fluid unless it's dirty.
It may also help to loosen and tighten the pressure relief valve bolt two or three times while the engine is ticking over.

Hi 2sm and techman,

Another thing to keep in mind about slow rising is that when Citroen changed to a 5+2 piston pump rather than the good old 7 piston pump they only allocated two pistons to the suspension. So now you have a pump 2/7 of the capacity of the old one. Now add another (hydractive) sphere to each axle and it puts the system volume up. Then consider all spheres are flat (or flatter than they should be) and now you have to pump a much greater volume of liquid into the hydraulic system to produce the same pressure to lift the bodyshell. Remember the pump only displaces a very small volume per stroke.

Slow to rise usually indicates flat spheres. (although a leaky pump feed pipe would give similar symptoms as techman suggests)

'Sudden' rises and/or falls indicates that the electrovalve is opening. However, its not opening frequently enough or at the right times. When the car is rising normally its because fluid is being pumped into the circuitry. The general pressure rises and the bodyshell rises to its normal height. If the electrovalve does not open during this time (and it should) then it doesn't see the general rise in pressure. When the electrovalve eventually opens it is then at a lower pressure than all the other spheres so fluid rushes from the wheel spheres into the centre ones. This has the effect of quickly reducing the pressure at the wheel spheres resulting in the sudden drop. For the sudden rise just reverse everything I've just said.

Sudden rises or falls indicates intermittent electrovalve operation.

Hope that helps.

Cheers

noz

I should of said this has been on going for a couple of years, and at least 10K miles since pump was checked.
Is there anything on the back end which could be sticking alowing excess fluid return causing it not to lift suspension and leaving the light on because its not building up the pressure?

Please ignore last post, what would cause the electrovalve fault? Is it the valve itself or in the ECU, etc? Where is the valve? Is there a way of checking the valve?
Cheers

Hi All

This is a 2.5 so it has anti-sink fitted so should not drop overnight anyway. What difference does this make?

Regards

XMexc

I`ve just had it running up in the air and if you jack the rear up and then let it down again the suspension drops and takes ages (5min on idle) to come up but in between while there is lots of clicking and hissing coming from hydraulics, lower pipe on anti-sink seems to click, and it looks to jump slightly on suspension.

Easiest thing to do is check the return pipes on the LHM tank (engine running), it sounds like you could have a biiiig leak somwhere, perhaps at the rear. My car was taking also ages to start raising from lowest, but since I've fixed everything it now goes to driving position in 10-13secs from an overnight low (non-antisink car). Bleeding brakes also a good idea. What u mean "regulator has been checked" ?

regards
George

Hi 2sm,

When you say

As far as I know lots of clicking is usually associated with a flat main accumulator sphere. I suppose the noise could be travelling down the pipework making it appear to be from the antisink.

The way it is moving up and down on the suspension suggests to me a problem with the rear height corrector.

Good Luck.

Hi, when I say up in the air I mean on a 4 post lift, with wheels on the ground.
Anti-sink - I thought this was an alu. unit, with about 5 3.5mm pipes going in to it, bolted to the o/s of rear axle - pipe coming out of bottom seems click/pulse.
Suspension jumping - the suspension seems to rise a few mm then drop -all very quick.
I have noticed that if you pump the brake say 4-5 times the hydraulic light will come on .

...sounds like u having a big leak somewhere for some reason, could even be the height corrector stuck open ,as demag suggests. Another member here has had the rear going up-and-down in a cyclical manner and he found 1 rear cylinder leaking badly. You would start the unraveling the thread of this problem if u looked at the LHM tank return pipes.

regards
George