When towing our caravan up to scotland a few weeks back the rear end of the car dropped slowly and then raised itself slowly with no drop in hydraulic pressure, this happened every 50 miles or so on a 150 mile journey but has never happened when not towing, any ideas? I also changed the lhm recently, could it have anything to do with the nose weight of the caravan as i did have a lot of weight at the front of the caravan and a lot of weight in the boot.

Sounds like a sticking rear height corrector to me, a few squirts of WD40 should sort it out.

Peter.N.

I do not see the spec of your car (if it is an XM.)
If it is a saloon XM, you must keep the towbar and GVW weights within the limits laid down by Citroen. I would expect the same to apply to a Xantia saloon. The XM estate has larger rear hydraulic cylinders so can accept quite a lot more weight depite the Citroen limits.
Better perhaps to transfer some of your car rear-end weight to the centre point of the caravan but be sure you are not overloading the caravan thereby. You are in a cleft stick!

I think Peter's right.

Derek