Hard Rear Suspension, Help

[jackyboy]

Now I know that this is a subject that has been covered a million times before but I really need some help here to rectify this problem on my 2.5td RP6750

To bring you up tp speed with all the info, I have just put the car through it's MOT, no problems at all. I drove the car up to Aviemore (80miles) to play golf and the car was fine. Maybe a little bit firm on the back but a non-citroen person would never notice. On the way back the rear suspension just firmed right up and I bounced all of the way home.
Next day I thought I would bleed the rear suspension (through the rear brakes) and gave it a good pump through. I then drove the car to Perth and back (60 miles) and it ran like a dream, really close to being the majic carpet ride.
Solved it I thought, went out yesterday and the rear suspension bounced all the way there and back.
Now, I want to fit one of E-Croftings mods but feel I need to sought out this problem first. One thing which may mean something is, when I return the suspension from high to normal, the car starts to go down gently then the rear end drops a few inches with a bit of a clump, then it goes down slowly again.
The car has done 68k from new, I bought it with 30k on the clock and have never changed any hydraulic parts, nor had the need to really. I had the car off the road for about 9 months, prior to that it was fine but since putting it back on the road I have this problem and when it firms up it is hardly driveable. Strange thing is, the front suspension is absolutely perfect.
Any good ideas? (apart from replacing everything. The bit I don't understand is how it can be fine one day and not the next. I would assume that if it was the spheres the problem would be consistant and not intermittent.

[demag]

Sticking rear height corrector or dodgy rear electro valve? With the ignition on can you hear a high pitched whistle down by the back wheel?

[jackyboy]

Hi Dave
When I switch the ignition on there is a definative click from the back wheel but not a whistling sound

Jim

[demag]

It's not very loud you have to get your head down there. A whistle normally indicates the rear electro valve working. You should also hear it at the front as well especially as you say the front is ok.

Mine was ok at the front and I could hear the whistle but nothing at the back and that was firm. I did a repair on the ecu and both work now.

Your not starting the engine are you? You only want the ignition on.

[Ciaran]

Definately worth getting one of the E-crofting kits anyway, it will rule out any problem with the rear electrovalve working intermittently / not at all due to the usual diode failute.

The sizzling sound made by the valves is quite distinctive. On a quiet night I can hear them if I unlock the car, without even listening for them specifically. I notice in my S2 when I turn the ignition to stage 2 before starting the engine, I get two distintive clunks from under the car when the valves energise. Are you only getting one of these?

Ciarán