2008 c5 x7 2.7 rear suspension drops

[Kenmac15]

Went out to my car on Sunday morning only to find the rear wheels buried in the rear arches, not an issue I thought started the car up & rear lifted no problem at all. All was good after that until last night & today, when the cars parked for more than 30 minutes it just drops so checked the oil level & all is good, checked the units & both bone dry so their not leaking. Any ideas please

[Harry5555]

Hi Ken,
had the same problem on my X7 some years ago. Actually there are three hydraulic pressure "balls ?" (Sorry, did not find the right word) in the rear of the car (five in total) - one for each tire and a ball placed in the middle of the car for comfort. Here also an electric operated valve is positioned.
If this valve does not close correctly due to age etc. the pressure in the rear drops to zero, so that after some time the tires have contact with the chassis.
With my car this happened now and then while driving and parking but kept getting worse over some weeks.
Therefore I gave it to the Citroen garage and the put in a new one for some 600 €. I was told that
a) these things never break down
and
b) was very hard to get out due to rust

Hope this helped.
Hartmut

[Jay-Bruce]

Harry has nailed it, it seems to be a weakness of the rear "firmness regulator". The "active" part of hydractive mostly pertains to it's ability to switch from softer comfort mode to firmer sportier mode as required. The way it achieves this by having 4 spheres on the rear axle, 3 on the front axle, one sphere is mounted directly to each suspension cylinder, the others are mounted in auxiliary valve blocks called firmness regulators, one sphere on the front firmness regulator, two on the rear one. The stiffer spheres are located on the suspension cylinders the softer ones on the regulators. The firmness regulator is also the valveblock through which fluid to or from the cylinders passes when the car changes height.

Normally, all the spheres are connected to the suspension cylinders, enabling fluid from the cylinders to squeeze the gas in the soft spheres more easily to give your vehicle the fabled citroen magic carpet ride. When the computer changes from comfort to sports mode, it sends a signal to the firmness regulators which energises a solenoid, which moves a pintle, which releases a pressure supply to operates a valve shuttle which shuts off the line from the soft spheres to the cylinders, and opens a path from the cylinders back to tank to discharge the fluid from the soft spheres. What seems to go wrong with them is the firmness regulator starts passing internally, allowing fluid to dump from the suspension cylinders back to the tank, and the dumping the fluid from the cylinders is what is lowering the back suspension.

Do you do your own mechanical work, or do you put it to a garage? There is a repair procedure to overhaul the rear firmness regulator that a C6 owner, CruiserPhil / PhilC as he was known in BX circles came up with that I can send you a link to, but this isn't a guaranteed fix. http://c6owners.org/plugins/forum/forum ... hp?2638.30

The next best option is fitting a low mileage regulator, and the ultimate solution is new regulator which is, as harry says, about five hundred quid. There is the added complication that the pipework on the back of these cars is known to corrode, so often presents a challenge to remove it, and some of it is a bit brittle, and doesn't like getting disturbed, making it likely to break when you start putting spanners on it. Coming off the regulator there are two pipes that run to large flexi hoses that go to the rear cylinders, they can be a chew to remove from the regulator on the vehicle, but can be more easily removed from the cylinders, enabling you to take the regulator and hoses off the vehicle as an assembly, and remove the hoses with the regulator secured in a vice. There is also a plastic pipe that has a brake nut type tube nut on it that goes to the return line, this is easy and safe to remove. The fun begins with the other brake-pipe-like tube nut on the regulator, which goes to a short hard pipe, which joins a short hose, which reverts to hard pipe before entering an aluminium union to the long high pressure pipe that runs to the BHI (pump/ECU/Tank combo in the engine bay), this fore to aft pipe, and the hose assembly it connects to both tend to corrode from the aluminium union.

You can do the CruiserPhil repair on the vehicle, but it's a pain, you're better doing it on a workbench, however that would mean disturbing that gnarly pipework, which is expensive, that fore to aft pipe is ~£350 new from the dealer, and needs fueltank and front subframe dropping to fit it. The little flexi is ~£180 iirc - I know this because I priced them up a while back. I'm going to be doing this job on my X7 soon, however, I'm NOT paying those prices for what is essentially a glorified brake pipe, so I have developed a system of special tube and custom made fittings that should enable a mechanic to make citroen LDS pipes for ~£10 in parts per end with a normal brake pipe flaring tool. I've got a small batch of these parts made and a stock of the tubing in hand, but haven't had the time to fit them on our car to verify the fit, and test them in use, but aim to do that soon. If doing the CruiserPhil repair doesn't work for you, I suggest you run the car, but keep an eye on it, push the raise height button to go to midpoint, lower back to normal height and wait on my fittings becoming available.

[citroenguy]

As far as i've been told you can unscrew the regulator solenoid and clean the pintle/piston. There is usually rust on it.
Can be done in situ, preferably on a lift.

[Jay-Bruce]

I'd already covered that:

Do you do your own mechanical work, or do you put it to a garage? There is a repair procedure to overhaul the rear firmness regulator that a C6 owner, CruiserPhil / PhilC as he was known in BX circles came up with that I can send you a link to, but this isn't a guaranteed fix. http://c6owners.org/plugins/forum/forum ... hp?2638.30

The link is to a C6 owners club forum thread showing how to strip the valve and clean it.