Rear Suspension Keeps Going Up And Down By Itself

[MadStu]

Hi all,

 

Yesterday I bought a 2001 C5 Petrol 3.0 v6 Exclusive SE. Its great! :D

 

I've noticed that when I park and lock it, the rear offside suspension keeps moving up and down by itself. I joked with my girlfriend that it's like Herbie, and it's wagging it's tail like an excited dog hehe, but is this something I should be worried about?

 

Thanks :)

 

Stu

 

[paul.h]

Welcome to the forum.

 

It is a sign of a problem, after the doors are closed the car should move to a level position in one go. In case it is a sticking height sensor, try taking the suspension up and down a few times to see if this helps. Also leave the steering in the straight ahead position (vaguely remember something about this) to see if it helps. Also the front and/or rear should move, not a corner on its own.

 

 

There is a pinned post on never going under the car without using axle stands, just in case you need to spray the height sensors with wd40. If the sensors are caught then the suspension can drop to a low height. The sensors are on the front and rear anti roll bars.

 

[MadStu]

Thanks Paul, it might actually be both the rear corners moving up and down, but being on the drivers side it's the only corner I noticed, lol.

 

Are the height sensors easy to recognise?

 

I've been leaving the car in the low position when I park it now which has stopped it from moving about by itself.

 

I'll see if I can find the height sensors and give them a spray, thanks again :-)

[paul.h]

Try a google search on C5 height sensor picture and from this you will be able to recognise them.

[Robhall77]

On an XM that I owned, this behaviour was traced to a faulty o ring of one of the rear struts. Because the high pressure o ring seal, the one closest to the suspension sphere on the suspension piston was not sealing, high pressure suspension fluid was passing straight to the leakage return tube and back to the reservoir. That means it's easy to diagnose, check the return flow to the reservoir by looking in the top of the reservoir. Any significant flow indicates a problem. The fluid leaks and the suspension drops, the height sensor caused high pressure feed to the rear spheres and the suspension goes up, leakage drops it etc. it was cycling up and down at about 3 cycles per minute.