C5 2006 2.0 HDI Exclusive - rear hydraulic piston issues

[estateFan]

Hi,
My C5 Estate exclusive failed it's mot three weeks ago. Rear passenger hydraulic piston area was soaked in fluid. I followed the information in a post by spiff , Dec 2017, and replaced the seals.
The problem is that the rear of the car now cycles up and down by about 15mm continuously every second or two. The lexia is not showing any related errors and after clearing the existing errors
it still has the issue. With the battery disconnected the car sits still, no gradual sinking.
I'm stuck without transport so will have to scrap the car if I can't sort it soon. Has anyone come across this or have any advice. You have all been so helpful in the past.
Regards,
Tom.

[xantia_v6]

Overshoot and oscillation of the suspension height is theoretically caused by one of:

- Internal hydraulic leakage
- Faulty height sensor
- Loose or broken link between the height sensor and the suspension itself
- Excessive mechanical stiffness in the suspension (seized bearing or hydraulic ram)

Does the suspension stay up if the car is left sitting with the pump fuse disconnected?

[estateFan]

Hi,
thanks for your reply
1. no hydraulic leaks that I can find.
2. Height sensor was working before replacing the seals so I assume it's still ok.
3. link joints were a little corroded so I sprayed them with wd40 when I was doing the seals. They are not stiff now but to rule out play as causing the problem
I also tied the roll bar ball joint to the height sensor ball joint with a strong elastic band so the distance would stay constant in the event of any play. Didn't help.
4. Trailing arm bearings are working perfectly, both rams are fine, no corrosion or stiffness.

suspension stays up with battery disconnected. ( I have removed the fuse specified as the pump fuse in the past but pump still runs so I always disconnect the battery ).

Next step might be to lock the height sensor arm in it's current position ( no idea how yet ) , then disconnect the roll bar clamp. If there is no suspension feedback to the sensor the car should not change height ?

Regards,
Tom.

[MGmike]

I was about to say pull the pump maxi fuse and get it MOT'd to give you more time to find the issue.
Then I was going to say, pull the overflow tube out of the rear cross member to see if the oil is escaping there but if it's not sinking it probably won't be!

It's most likely connected to the work you've done but I'm struggling to think what it could be!
best of luck with it...

[estateFan]

Solved
----------------
You were spot on, it was related to the work I did.

When I re-attached the link bar clamp to the roll bar, at the other end of the link bar the height sensor arm was was pointing up and towards the back of the car. It should have been pointing down and towards the front.

I found a photograph from the last time I worked on the suspension that showed the correct position.

This totally confused the car because the rotation of the arm was now opposite of what it should have been. The car tried to raise itself but the sensor said the car was dropping.

Once the height sensor arm was in the correct position I could see a 5mm hole in the arm that lines up with a 5mm hole in the sensor body, if that helps anyone in the future.

The two hydraulic seals that sit in the single groove inside the cylinder are the devils work to get out. The first hard neoprene seal, the one that's visible, hides a softer seal behind it. I took a sharp fishing hook, filed off the barbs, wrapped very thin wire around the shank, gripped it with a pliers and then used a large hose clip to force the handles of the pliers together. Otherwise the hook twisted. I could push the pointed end of the hook down between the edge of the seal and the edge of the groove and turn it slightly to get under the seal. I did that for each seal. Nothing else worked. This was all done lying under the car.

Also, the wire gaiter clamp is very difficult to get back on. Last time I made a tool by filing a 90 degree 250mm long nose pliers so that one of the pointy ends was shorter and thinner. The 90 degrees means both blades stay parallel and don't slip off the wires when you're closing them together. I guess there must be a factory tool.

Many thanks for all your suggestions.

Tom.

[Gibbo2286]

I did the gaiter on mine last week, couldn't get the clip back on so at the moment it has an ordinary hose clip, a new clip from Citroen is now no longer supplied, I'll have to find a screw type wire clip when the mood improves.

[estateFan]

I couldn't get the clip back on either until I made a tool to do it. If someone can tell me how to upload an image or how to email one, I will show you what I did.

[myglaren]

There is a guide to uploading images to the forum here!

[estateFan]

Image copyright Tom (estateFan). Taken 23 Oct 2021.

gaiter clip tool. Nearest point filed to sit into "u" shaped wire on clip.
Farthest point is longer to sit over the wire you are trying to pull the "u" wire onto.

Tom.

[MGmike]

Tom, can I borrow it for a couple of weeks please?

[Gibbo2286]

I didn't need the pliers just the weather to change, I started ok then with oil running up my sleeve and lying on my back out front it peed down with heavy rain.