Sinking XM?!

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Citroenmad
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Sinking XM?!

Post by Citroenmad »

The low mileage Xm we recently got has started to sink at the rear when parked for a few hours.

It was fine when we got it, it had been stood for 8 months and in normal heigh and had not sunk to low. The spheres were badly in need of replaceing though, the rear was solid.

The day after we collected it it sunk down at the back, thinking it would be spheres we replaced them first, as they needed doing anyway. No joy.

So the anti sink valve was the nest thing to try, a new genuine Citroen unit was fitted yesterday and its still sinking down.

The rear brakes also stopped working at the same time as it started to sink down (this was before it passed its MOT). We bled the brakes, lots of air was in the system, probably nitrogen out of the spheres? Not sure if this is related in anyway, as it seemed the spheres had pressurised the brake system.

Any help? What else could cause this?

Thanks, Chris.
Chris
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Ciaran
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Post by Ciaran »

Leaky brake doseur.
Citroenmad
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Post by Citroenmad »

I should have said, since bleeding the brakes they have worked fine and its passed its MOT since then too.

I did think the brake doseur, might be the next thing to try then. Thanks.
Chris
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Ciaran
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Post by Ciaran »

Basically, the valve leaks internally, resulting in a slow (and later, quicker) drain of pressure from the rear, back to the reservoir. This is irrespective of brake performance.
Have a look at the the volume of fluid coming through the return hoses to the LHM tank.

Ciarán
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Post by FrenchLeave »

The brake doseur, like the height corrector and the misnamed antisink sphere, is on the wrong side of the anti-sink valve to cause this problem. In fact that is the reason the anti-sink valve was fitted, to prevent losses through those "leaky" components causing suspension sink when parked.

So the leakage must be inside the system that is sealed off by the AS valve.

There have now been three incidents to my knowledge (one of them was my V6) of a leaking rear suspension cylinder. The proof, as Ciaran wrote, is to check the return hoses. Or you can pull off the return lines from the cylinder bellows for a direct leakage check, car on ramps please. If it is the cylinder it will of course leak continuously with the engine running.

One of the symptoms of my car was that, in stationary traffic, the rear would drop until the HC corrected it, it would then rise, the HC would close, the rear end would drop etc. etc.

Derek (DerekW on the other place)
1999 XM V6 Exclusive, Black
1994 XM 2.0 TurboCT estate, green of course: now gone to no3 son
2004 C3 1.6 auto exclusive with Sensodrive - the wife's but she doesn't like it
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hirsty
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Post by hirsty »

Does this also apply to Xantias? Despite recently replacing all my spheres, when I stop the car, the rear sinks 4-6" within seconds. When the engine is running, the accumulator ticks way too much. I thought it may be the doseur valve, but now I'm beginning to wonder.

Keith
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Post by Deanxm »

Sounds like you have a very substantial leak there, it would be worth checking the rear strut returns as per Derek's post.

Chris, Hasnt your new XM only got 30k odd on the clock? seems a bit early to have strut failure, wasnt there an Electrovalve seal that would fail and cause the car to drop, not too up on H2 so im ready to be corrected here

D
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Post by Citroenmad »

Thanks for the replies :)

The car stays level when the engine is running, it doesnt sink down then. It sinks down when its been parked for about 3-4 hours. Its quite quick to return to normal once it has been started.

Hi Dean, yup its only done 31000 miles, it was sitting level for a few days (and for the 8 months while it was stood before we had it) but then something happened and the rear brakes went off and it started to sink at the rear. We bled the brakes and they are back to normal now, but its sinking.

Would a failed strut not be gradual, or would it be a sudden thing? Id have thought struts would have been fine at this mileage and given the cars condition. I hope its not that.

When we did the spheres, we pressure tested the ones we took off, i think the antisink was still up to a good pressure, 30 if i remember rightly. So it obviously was not that.

However both rear soft spheres were totally flat and totally filled with fluid.

Ill pass your info onto my dad, who knows a lot more than me! We just wondered if there is an obvious cause. Will check the return hoses first.

This car is getting expensive :roll: Mind it doesnt half drive well! :D
Chris
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Post by Deanxm »

Sound like the leak isnt massive so when the engine is running it keeps itself pumped up, i am thinking the same though, you havnt covered enough miles to have worn cylinders so IF it is them leaking you should be able to put new seals in no probs. If its the EV in the hydractive block im not sure, ive never taken one apart so i dont know if its a cheap 'o' ring or a new valve..........

Good luck

D
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Post by FrenchLeave »

I recall that Noz wrote a screed about leaking rear cylinders. If I remember correctly he wrote that the problem is caused by the rear suspension geometry which means that the pushrod isn't always acting in line with the piston. This causes wear on one side of the aluminium cylinder and when the surface breaks up -and this happens quite suddenly - heavy leakage occurs.

Your leakage rate is certainly not in that league and I doubt it's enough to give much of a show at the return lines. I was expecting something like my V6 on 50,000 miles when if you parked it and came back five minutes later it had adopted the praying mantis position.

Derek
1999 XM V6 Exclusive, Black
1994 XM 2.0 TurboCT estate, green of course: now gone to no3 son
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FrenchLeave
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Post by FrenchLeave »

A belated reply to hirsty, yes the Xantia has the same rear setup so you should be checking the return lines for a regular fluid flow.

Derek
1999 XM V6 Exclusive, Black
1994 XM 2.0 TurboCT estate, green of course: now gone to no3 son
2004 C3 1.6 auto exclusive with Sensodrive - the wife's but she doesn't like it
1994 ZX 1.8i auto - the wife's new baby

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Post by Citroenmad »

It 'seems' to have fixed itself! :D

It had a good run yesterday on a CCC drive event, which seems to have done it some good. Its only done 450 miles since being back on the road, so maybe it just needed using.

Might have spoke too soon, but it was still in normal height this morning when i came to get it out of the garage.

Hopefully that willo be the end of that :lol:
Chris
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Post by steelcityuk »

The failed O ring on the Electrovalve would probably be the one that failed on my Xantia.

Image

Before the hydractive valves shut the car made a sound like a cistern filling.

Steve.
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