C5 rear suspension fault

[fastjet]

Hi, I need some advice please on a rear suspension fault that has suddenly happened on my MK 1 C5 as I am struggling to diagnose the fault. I will try to keep what has happened so far as brief as possible to avoid a lot of reading.
The rear suspension raised itself to the 24 mph height.
Pressing the ride height adjuster in the car does not make any difference.
When I got back home, I connected lexia and ran the diagnostics which showed no faults.
Using Lexia I activated the rear suspension, raise and fall, no change in ride height. But you could hear the pump and switching taking place.
I then used Lexia to depressurize the system and the suspension lowered to its bottom stops.
Using Lexia I activated raise, again you could hear the pump, sounds of some switching sound at the back of the car, but the suspension did not raise.

So, it would appear that there are no faults, but the rear suspension will not raise. The front works fine and responds to Lexia commands. I have checked the plastic connection rod and that appears to be ok.

Any ideas on what might be going on?
Many thanks.

[MGmike]

You don't say if the suspension in 3 or 3+ but I suspect the rear centre valve may be stuck.

[fastjet]

Hi MGmike. Thanks for the suggestion. What do you mean by 3 or 3+?

[Hell Razor5543]

The suspension on the C5 has two 'versions'. H3 is the standard version, while H3+ has the option of switching between standard and sports mode. The simplest way to see which version you have is to look at the height switches. If there are two (up and down) you have H3, but if there is a third (sports) button you have H3+.

[fastjet]

Hi Hell Razor5543. Thanks, it is a 3.

[GiveMeABreak]

He only has standard suspension - not hydractive 3+, so won't have a rear centre sphere, so I would be suspecting the rear height corrector as being faulty, or the BHI - possibly one of the eletrovalves is stuck.

[fastjet]

Hi GiveMeAbreak, thanks for your reply.

What is BHI short for and where will find the eletrovaves?
Thanks

[wheeler]

Built in Hydroelectric Interface.
The electrovalves are an integral part of the BHI.
The front & rear body height sensors are the same part, you could swap them front to rear & see if the fault moves.

[fastjet]

Hi wheeler, thanks for your reply.

I am now getting a better understanding of how the suspension works.
I'll try swapping parts if nothing is obviously broken.
Thanks

[fastjet]

Does anyone know what the normal ride height values should read in Lexia?
Thanks

[GiveMeABreak]

You will have reference height values and the actual values shown. These are not representative of actual heights though - they are calculated values, so don't go and change anything there at this point.

Height Checking Procedure:

viewtopic.php?p=656405#p656405

[wheeler]

I'll try swapping parts if nothing is obviously broken.
Thanks

A bit of advice, take pictures of the positioning of the height sensors before you remove them as they can be positioned the wrong way around

[Hell Razor5543]

Also make CERTAIN that the car is properly supported before doing anything that affects the suspension. If a Citroen 'decides' to drop it can drop very quickly, and if you are underneath when it happens (and she is not supported) she WILL kill you!

[fastjet]

Hi Marc, thanks for the height measuring information.
Should H1C = H1M as it says compare them?

Well I have had an interesting day on the C5. I feel that I have joined the forum properly now having earnt my C5 stripes today.
I managed to the car of the ground enough with a jack for the suspension to hold the weight of the cars. I then raised the car to the 24 mph setting. The front lifted but the back didn't. So I lifted the back with a jack and the suspension held the weight. I was then able to reverse the car onto a pair of ramps. Based on people's advice I popped the link rod of the height level sensor to see if it was seized, sensor arm was moving freely. I remembered reading a post on the forum were some one else had had ride height issue. So I removed the sensor found the post and followed it for guidance. Inside the sensor was clean and the board is just push fitted as the original posters board was. So I soldered the pins onto the board, refitted and dropped the car off the ramps. The back of the car then responded to height selection although the rear height wa obviously to high. Back onto the ramps, then I marked the clamps position with paint for reference and adjusted until front and back looked about the same. A quick road test brought some unexpected results. There is now much less of a thump when going over potholes and the car turns into corners better. I guess that the suspension must have been failing for a while. Having looked at how the height sensor is made I wonder if it starts to send false and correct readings which cause fluctuations in the suspension. If the weather permits I will do a ride height check tomorrow.
Thanks you for the advice.

[fastjet]

Thanks for the warning, I took great care. Put the car on ramps and I put axle stands under it. When the suspension depressurizes they real do sit on the floor and it definitely crush you to death! I put paint on the clamp to mark it, but I suspect it has been played with in the past and it might not have been put back on correctly. So I am now searching the internet for a photograph showing what it should look like when fitted correctly.