C5 x7 2009 136hdi Hydro woes

[Jim66a]

Hi, has anyone had experience or advice on this problem?
When driving along, the rear of the car will either suddenly jump up or drop down from normal. It corrects itself straight away. Sometimes the rear drops overnight. I start the car and the rear will start to rise, stop for a few seconds, then suddenly jump up and continue to normal position.
I have a Lexia and Delphi so can see the position of both front and rear sensors moving. The rear positioner counts upwards, stops until the car 'jumps' then continues to count quickly without a gap until it catches up. I assumed that this was just the position damping in the software. So I don't think the positioner at fault. I have changed the rear position dog bone as was worn but this made no difference.
No faults are recorded.
Any help gratefully received.

[Jim66a]

Its 2009 not 2008!!

[GiveMeABreak]

Could be several things Jim.

Either a faulty rear height corrector (these do go faulty internally as the tracks wear) where the data can be sending a faulty reading, or it could be the rear hydraulic block. The electrovalve can start sticking where it allows fluid to return to the reservoir causing the drop and then correction.

[myglaren]

It has been observed that the height correctors can become faulty - burned or dirty tracks. Some have had water ingress.
Sometimes they can be removed and cleaned but usually a replacement is called for. Not expensive, around £35 from the dealer IIRC.

[Hell Razor5543]

It could be worth checking the LDS level. I had an issue with my current C5 in that the suspension was 'off' in behaviour, and I found the LDS fluid was below the 'min' level. Topping it up resolved the issue (it was possible that, on occasion, air bubbles got drawn into the system and then made it into the suspension struts, causing poor ride quality).

[GiveMeABreak]

It has been observed that the height correctors can become faulty - burned or dirty tracks. Some have had water ingress.
Sometimes they can be removed and cleaned but usually a replacement is called for. Not expensive, around £35 from the dealer IIRC.

Only halfway there Steve, £74 for the rear £67 for the front inc. VAT.

[GiveMeABreak]

It could be worth checking the LDS level. I had an issue with my current C5 in that the suspension was 'off' in behaviour, and I found the LDS fluid was below the 'min' level. Topping it up resolved the issue (it was possible that, on occasion, air bubbles got drawn into the system and then made it into the suspension struts, causing poor ride quality).

It won't be low fluid James. The warnings and messages would come on way before it got to that level. Besides low fluid would not cause it to drop and rise. I've seen this happen before - usually the block if not the height corrector.

[Jim66a]

I am thinking its probably the block as I can see the height corrector working correctly and the harshness of the movement when it jumps is more like a sticky valve opening rather than the slow movement that the corrector would provide.
I'll bet they are expensive!

[myglaren]

They increased in price rapidly - or are the X7 ones different to the Mk1 & Mk2?

[GiveMeABreak]

Yes they are different Steve. The X7 uses a similar but different BHI, piping, struts, and supply and return system / block.

[GiveMeABreak]

I am thinking its probably the block as I can see the height corrector working correctly and the harshness of the movement when it jumps is more like a sticky valve opening rather than the slow movement that the corrector would provide.
I'll bet they are expensive!

Jim, have a squiz here on Citroen C6 Owners site. It is the same system - but shows the rear hydraulic block issues that I was talking about:

http://c6owners.org/plugins/forum/forum ... hp?2638.30

[Jim66a]

Thank you Marc, After reading through that C6 thread, I'm going to give the rigidity regulator spool a clean up.
I need to get some LDS fluid as don't have any so as much as I want to go strip it down, I Darent do it until I can top up.
Many thanks to everyone who has contributed.

[Hell Razor5543]

You can get LDS fluid from GSF, normally at a much better price than from a dealership.

[Jim66a]

Update: This morning I took off the firmness control solenoid and found the actuator pin to be sticking as though the tube it slides in was no longer round.
The solenoid cap looks deformed so maybe internal corrosion is slowly crushing the tube?
This would explain the sudden changes in height and the dropping overnight as the solenoid pin controls the spool pilot needle.
I have attached a video and pictures showing the sticking pin and cap deformation.
Off for a trial drive now...
Not sure how to add the Mp4

[Jim66a]

I have just done 10-12 miles of jolt free magic carpet of old ride... Its not far, But I was getting a jolt within a mile of home previously.
I ground the pin so that it moved freely up and down inside the solenoid coil on any position of rotation and then polished it. Obviously this is a temporary fix and I shall be on the lookout for a good used valve assembly or solenoid.
Thanks for all your help and hopefully I have found the solution.
Have a great, safe Christmas.