Pitching Along... ~~~~~, Always somethign new Pt. II

[Michael P]

Hi
Just recently bought my first XM (had CX and BXs). Just wonder if anyone here has come across this problem - pitching movement of vehicle during acceleration and deceleration. I had a similar problem with my CX, the suspension in the rear was way too soft even with new spheres. I was never able to find out why. I have actually hit the rubber end stop in a dip once. In the BX we found from experience that the pitching movement (esp. nose down when braking) normally originates from and air lock in the rear brake system. Bleeding them normally cured that.
But just in the CX or a bit worse the car goes nose up on acceleration and then (never had that on the BX or CX) the regulator recharges the accumulator three to four times until the car is level. Then everything is fine. No otherwise worrying symptoms. Lovely ride otherwise. This behaviour is against the design aim of the suspension. I need to think about this one a bit more, maybe I find some enlightenment. Will try to bleed the brakes if time allows.

Michael

[Peter.N.]

If the suspension is that soft, I would suspect that someone has fitted the wrong spheres, or the centre one on one of the suspension cylinders. I have fitted comfort spheres to mine and the ride still isnt as soft as the CX but certainly an improvement.

Peter.N.

[Michael P]

Well, I don't know about that as I just got the car. The ride is perfectly pleasant but as I said it is going nose up nose down. With regards to the spheres I believe the car was always maintained by a Citroen garage. One would ass-u-me that they fit the right ones. My experience with C- garages however tells me that they don't know the difference between a CX and an Apollo moon rocket. That's why I drive them, they are cheap because they haven't a clue.

[Peter.N.]

Just a thought, I suppose that the height control valves are not sticking? It might be worth spraying the linkage with WD40 over a few days, especially if the car has been standing for a while.

Most of the people that write on here know more about XMs than Citroen do!

Peter.N.

[Michael P]

No Peter, I think the HC are fine, the car goes up and down smoothly on request. Sometimes there is some jerking as the car does some pitching (rare) but I suppose that is when the HCs get into action. Also there is a condition when the Hydractive system does some input when it shouldn't. I need to look into that again. All that up and down business appears to be OK.
BTW aren't there any (ex) Citroen engineers here on the web that can give us some valuable, much required info? I don't know about you Peter but I was thinking of a hydraulic FAQ where all the (common) problems and remedies are listed. Somebody would need to put it together though. Wonder if it exists.

Michael

[Peter.N.]

I am afraid its a new one on me, I have run hydropnumatic Citroens for about 20 years and 500k+ miles, but I have never come across that problem.

Peter.

[Michael P]

Thanks all for your input here but just to give you a little feedback here to close down the topic. As I had expected and mentioned before I had a suspicion that there is air trapped in the dead end pipes to the rear brakes. I checked that yesterday and indeed, while bleeding the brakes several bubbles made it into the bleed vessel. On the right more than to the left. LHM in those dead ends always looks a bit sorry. Anyway, long story short, bleed nipples tightened and the problem is now vitually eliminated. Amazing what a problem a few bubbles of air can generate.