Xantia groaning

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bruno
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Xantia groaning

Post by bruno »

Hello, it's me again...

When turned off after a longish ride (+- 30min drive), the front of the car lowers emitting a groaning noise, as if letting pressure go. When the security valve closes, the noise stops and the car stands still. No sink overnight (it's an anti-sink model, hydropneumatic).

I've just replaced the brake doseur, but the noise remained. I don't see any noticeable flux from the return pipes. Where should I be looking at? Front height corrector? Or I needn't to be worried at all?
Xantia SX mk. 1 2.0 16v petrol hidropneumatique
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Post by RichardW »

They all do that to a greater or lesser extent. The cause is fluid coming back from the height corrector past a partially closed anti sink valve causing a pipe to vibrate aginst the bulk head somewhere. There was an official Citroen 'fix' (they were doing it when still under warranty!) which involved wedging a piece of rubber behind the pipe - never worked too well! I think it should be minimised by making sure the accumulator is in good condition, and the LHM is relatively new - the fact that it occurs more when the LHM is hot suggests it is somewhat viscosity related, and new LHM is generally thicker than old.

Otherwise, it's just one of those Xantia things :lol:
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Mandrake
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Post by Mandrake »

Agreed.

On my car at least, I'm pretty sure that the trigger for the noise is that there is insufficient main system pressure left at the time that you get out of the car and the height corrector attempts to lower the car, with the flow of oil causing the anti-sink valve to oscillate, and the pressure oscillations cause one of the pipes to vibrate against the bulkhead.

It can sometimes groan for 10-20 seconds. Anything that causes the main system pressure to drop quickly after the engine is turned off will make the groaning noise MUCH more likely.

This could be a flat accumulator sphere, or an internal pressure leak in the system somewhere - such as a leaky hydractive electrovalve. (The latter is the culprit in my car, but it's too expensive to replace it)

Basically if you have a short time between pressure regulator ticks when the engine is running the car will have a tendency to groan when you get out, if the regulator cycle time is good and long (1 minute plus) it probably wont. :) (unless you sit in the car for some time between turning the engine off and getting out)

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
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falling-out-with-my-car
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Post by falling-out-with-my-car »

My old Diesel BX used to do this a lot until someone suggested pouring a little lhm down the inside of the offending suspension leg through one of the plastic caps mounted on either side of the top of the strut.
even the mot station gathered that was what I had done to lubricate the leg, over time that leg actually seized.

it may be something completely different in your case my xantia groans sometimes, but only in very damp mperiods of weather say a week or so.

regards Nigel.
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bruno
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Post by bruno »

Ok guys, thanks for the answers.

It seems I have to find the cause of pressure dropping. I'm sure the suspension struts are okay since I don't have flux from the return pipes. The clicking is rather frequent (5 secs or so), and I assumed it wasn't because of the accumulator, because it was new. As other symptoms were there (dropping of the back when brake pedal pressed, pulsating brake pedal, etc.), I thought the doseur were at fault.

Changing the accumulator is the next step then. At any rate it is good to know the groaning isn't another problem.
Xantia SX mk. 1 2.0 16v petrol hidropneumatique
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