Citroen C5 MK2 2005 rear hydraulic suspension dropping

[birca]

Hi, I need your help.

C5 MK2 2005 dropping the rear suspension to the floor in cca 8 hours. I have no leakage of the LDS oil, i depressurize system with Delphi diagnostic tester. LDS oil is between A and B level.
I look for the rear stiffness regulator (like in the picture, part 2), but I couldn't find it on my car.
Please for your help or any advice.

[wheeler]

Probably an (internally) leaking rear cylinder. It will be leaking back into the return. You can pull the return pipes off & leave containers underneath to see if any fluid leaks out after a few hours.
Of course make sure the car is supported before getting underneath.

[cit-rotti]

According to the picture, your Citroen does not have an H3+, i.e. no additional sport button, but only the normal height switch.
That's why it doesn't have a hardness regulator, but only a distributor for the left and right spring cylinders and only thinner 3.5mm high-pressure lines. But mostly it has 40mm pistons, for which all spare parts are still available.
The only way to find out exactly is to check the chassis number.

It is easy to judge whether the rear spring cylinder is defective - the vehicle does not maintain its height and drops relatively quickly. Normally the C5 does not sink for weeks. The faster it sinks when stationary, the more likely it is that there is an internal leak. However, 8 hours can still be tolerated.

There are 2 sealing elements installed in the cylinder. The inner element consists of 2 parts: a rubber ring and a sliding ring - if this is defective, the LDS flows back into the tank via the return line on the sleeve - there is normally hardly any LDS in the sleeve, which is basically more of a dust cover. As the rear spring circuit is connected to each other, all the hydraulic fluid flows out via the return line of the defective spring cylinder.

However, the sleeve also has a second emergency overflow, which flows into the axle tube. Then not only is the 1st sealing element defective, but the 2nd sealing element is also damaged (O-ring) and both the rubber sleeve is filled with LDS and sooner or later the axle tube and the hydraulic oil is then of course missing - it does not flow back.

If the piston of the spring cylinder is not also damaged, a workshop can repair this very well - these parts are still available from Citroen for the cylinders with 40mm pistons. The spring cylinder has to be removed anyway - a fun job if everything is rotten.

Although the right-hand spring cylinder (5272 69) is no longer available, the left-hand spring cylinder "5272 70" is. Right and left spring cylinders are basically identical - only the retaining plate has to be turned and the clamp positioned differently.

The original parts can be purchased from any lemon dealer.
For a 40mm piston, these would be the following seals:
5272.28 O-ring
5272.30 Sliding ring
5272.32 Rubber seal under the sliding ring
The O-ring (NBR or Viton) and the rubber ring under the Teflon ring (sliding ring) do not cause any problems - only the harder sliding ring is not easy to insert without damage - and it must remain intact.
It may also be necessary to replace the sleeve, the 2 M8 screws (Torx 40) and the sprint - but they won't cost the earth.
And the sealing elements of the LDS connection must not be lost during removal.

Normally, it is possible to check which spring cylinder is leaking via the returns - sometimes it is both. To do this, the vehicle is brought to its highest position and must be standing on all 4 wheels - either on a pit or on a 4-post platform - access ramps are also available and never work under the vehicle without such a safety device - do not even look. Then remove the return lines (not the overflows that go into the axle tube) from the sleeve and seal them, otherwise the returning LDS fluid will empty out of the reservoir.
Instead of the return lines, insert short plastic tubes into the sleeve and allow each to flow into a collecting vessel.

Where there is little or no LDS, everything is fine - the LDS flows out via the defective cylinder until the rear end has sunk. Of course, you don't have to wait that long - the problem becomes apparent immediately and the short plastic tubes can be removed and the returns plugged back in.

Even in the lowest position, there is still a fair amount of residual pressure in the system. The hydraulic system must therefore be depressurised before dismantling the spring ball and removing the cylinder - ideally with the LEXIA or via the bleeders. If possible, the spring ball should be released with a small jolt while it is still fully pressurised so that it can be unscrewed more easily when depressurised.

Greetings Wolfgang

[birca]

Thanx Wheeler and especially Cit-rotti !

Today I looked under the car and found both cylinders in bad condition, especially right one.

This is return line, marked with red? This weekend will test in my friends garage.

Does anybody have access to look in catalogs (VIN number), if I have cylinders with part numbers 5272.70 and 5272.69?

[cit-rotti]

Does anybody have access to look in catalogs (VIN number), if I have cylinders with part numbers
5272.70 and 5272.69?

The data/spare part numbers via the VIN from the current Citroen Service Hotline are available for every "donor" in this super forum.

Greetings Wolfgang