My XM sinks down overnight. Well, it sinks down only after a few hours. I've actually read an answer on this on the Yahoo group, and Norrie also sent a reply to my in some personal correspondance. He's going to post that reply on this site for everyone to use.

Sinking suspension - the culprit is either worn suspension struts or worn height correctors. Either will return leaked fluid to the tank. The height corrector is the most likely. You can tell which component is leaking worst by taking off the return tubes at the tank end one by one. The one with the most fluid flowing back to the tank is the circuit with the most leakage (only try this with the engine stopped otherwise you'll get soaked !)

From the position of the return pipe you can tell which component is to blame.

Flat spheres aren't the main cause but can add to the problem due to the lack of 'storage' in the system. The pressure left in the spheres can be measured using a home made setup if you're a bit handy. Otherwise you can have them measured at a Citroen agent or an independent.

Cheers

noz 8)

sorry, the brake valve is another possible culprit. The rear brake pressure is obtained from the rear suspension pressure. If the brake valve is leaking the fluid from the rear suspension will find its way back to the tank.

Having said that the priciple of finding the culprit is the same. Identify the return tube with the greatest flow back to the tank. Either trace the tube manually back to the leaky component or consult the manual which will tell you what component is connected to what return tube.

cheers

noz 8)