Rear End Won't Rise

I changed the spheres in my Mk2 2.5TD the other day, and the front end is working as normal, but there is no fluid getting to the back suspension.

Any ideas where to look for a solution, please?

Without knowing your experience level, have you checked the white plastic clip that attaches the height selector rod to the rear height corrector? Maybe you knocked it off whilst doing your spheres.

They often pop off and are the main reason for the rear not rising.

Hi wirdy,

I've plenty experience with hydraulic Citroens over the past 20 years - 2x GS, 5x BX, 1x CX(currently SORN), and this is my 2nd XM. Its just I've never worked with hydractive before.

I have already cleaned out the height corrector, and double checked its connections. The front end works fine, but there does not seem to be any fluid reaching the back end, as brakes cannot bleed - no pressure.

I have just split two of the front-to-rear pipes at their joints (under rear door), but could not get much fluid out - a dribble for a few minutes - with lever in high and engine running.

It seems too much of a coincidence that something might go faulty as I'm doing a job, so I've probably induced it by not adhering well enough to the requirements..

Oh, the plastic connector on mine is black.

Gordon

Hi Gordon

That's a new one on me. I wonder if there is a seperate feed to the rear suspension from the distribution block and that has developed a fault? As you quite rightly say if you have no pressure in the rear suspension, you won't have any rear brakes either. Presumably you have checked the input to the height regulator for pressure, if there is none there it can only be a failure of the feed to the rear, but where? I have tried to find the layout for the breaking system, but unsuccessfully I am afraid. Let's hope someone else on here has had the same problem and can throw some light on it, otherwise it's 'trace the pipe' time.

Peter.N.

There will be no pressure in the rear braking and suspension system unless both the rear wheels are on the ground ( or both standing on blocks). There is a cutout valve which prevent fluid reaching the rear brakes unless the suspension at the rear is under pressure. (Explaining why the rear brake pads last so long unless you are in the habit of carrying a load in the boot).

Hi Gordon,

According to my system diagrams the supply to the rear suspension and rear brakes comes direct from the security valve. This requires a pressure of 80 bars to open the supply line, but as the hydraulic warning lamp is set to 80 - 110 bars the supply should be present when the lamp is out. Suggest you start your investigation at the security valve as it looks as if, for whatever reason, the valve isn't opening.

Derek

Derek - is the security valve the same thing as the priority valve? That's where I'd start looking.
No other reason why the rear hydraulics should be isolated.

Citroen seems to use different names for the same components. The security valve is also called priority valve or distribution valve.
Your problem couldn't be a stuck anti-sink (SC/MAC) valve, as you said you split the supply line to the rear. So it would seem it could only be the security valve, as the feed to the rear comes from here. BUT, I seem to remember that high pressure is fed simultaneously to front and rear from this valve . . .

I'm not aware of such a special valve, would u know how is it called? Where is it physically? You're not speaking of the security/priority valve, are u?

cheers
George

Exactly, on a pas car, the piston in there first opens the way to the (front) brakes and then it moves further to reveal the front and rear suspension feed pipes which are face-to-face. So in this case it could only be the rear suspension feed pipe that has blocked just after the security valve.

cheers
George

I'm not aware of such a special valve, would u know how is it called? Where is it physically? You're not speaking of the security/priority valve, are u?

cheers
George

Whenever I've had my cars on the ramps with all 4 wheels in the air I have had no difficullty gettting the fronts and rears to pump up & down or to bleed all 4 brake calipers.
If I have this cut-out valve on my cars it cerainly ain't working too well!

Hi all

When mine is up on axle stands and i start it up it up it will not pressurise the axle that is off the ground, but this is because the wheels are hanging down and so the Height corrector is trying to release pressure to get the car to sink because the wheels hanging make it think it is already pumped up..............if that makes sense , The system is not capable of lifting a wheel up, it uses the weight of the car to push the fluid out of the system as an when the HC (via the anti roll bar) dictates.

Absolutely, although have you tried changing wheels by exploiting the force of the antiroll bar? A classic show-off with hydraulic Cits.

Put car "higher" or "highest", place jack front or rear (doens't matter), put car to lowest, watch both wheels at the jack's side go up in the air as the other side goes down!

cheers
George