Citroen XM Forum

I will see these days to change the LHM oil in the entire system, to clean the height correctors, it sometimes occurs that the front brakes first then the rear brakes.
Maybe it's the valves, I don't know what they are for, probably for the height, sometimes you hear a screeching, strange noises, when I turn off the car until it reaches a certain height, maybe those valves also have some influence on the distribution of braking pressure.

That is an anti-sink valve, which blocks the flow of hydraulic fluid from the suspension when the pump ceases to generate pressure.

I wouldn't have thought they would cause a pressure imbalance in operation as the height correctors will keep the car at the correct height, irrespective.

Are you sure the car only behaves like this sometimes. It's possible you are noticing the rear lift after lifting off the accelerator just before braking.
I've also remembered you car isn't fitted with Hydractive, so it will have greater body movement under acceleration, braking and cornering, than a Hydractive equipped car does.
A non-Hydractive Xm isn't as balanced as a Bx, so you just may be detecting the difference, given your long term car was a Bx.

Run Hydraflush and see if there is any change. The anti-sink valve shouldn't be squealing, which indicates passage of fluid, so it may be sticking, or have dirt in it.

My Xantia (VSX) would groan like a camel if I remained sitting in the car for a minute or two after switching off the engine. Someone did tell me the likely cause, but it had no effect on the performance of the hydraulics. We just accepted as normal "quirky" Citroen behaviour.

The anit sink sphere also arrived, at the same time the complete LHM oil was replaced, the pan and oil filters were washed.
..pressure good.

...catastrophe filters as dirty as they are.

Replacing the anti-sync sphere is only possible if the last two screws are removed from the beam and the rear part of the chassis is lifted with a crane, so that a sufficient distance is made so that the sphere can be pulled out with its support.
...mandatory use of water tongs.
...rear bolt.

...required gap of the trap from the chassis to pull out the sphere.
...new oil for the anti sink sphere as well

...at the end, a new sphere was placed.
I did not take a picture, a pictorial representation for explanation, raising the sash.

while this is a good time to use it to replace the heating radiator, the good thing is that it is very easy to change, at the same time I also replaced the brushes on the fan, while it was all disassembled I also checked what the situation was with the air conditioner, I was not very surprised what did i see :

...everything was dismantled and cleaned, there was a lot of dust and various rubbish.

...pictures of the air conditioner cooler, it was immediately clear to me that I had to clean it as well, and it can only be reached if everything is disassembled and taken outside, if it had a new cooler to buy I would have bought it too, it's just like this cleaned, washed with various lubricating fluids .

...this is the front side, the inlet side where the fan blows it.
...this is the exit side, the side towards the interior of the cabin.

I sensed the problem with the air conditioner on the first day when I topped it up, I noticed that the compressor works for 2-3 minutes and then turns off, after some time it turns on again and everything works like that.
When I saw the condition of the refrigerator, everything was clear to me, since there is no good air flow, the refrigerator freezes, so the temperature sensor disconnects the compressor so that there is no overload in the system, when the ice melts, it turns on the compressor again and so on in a circle
.

...and so I started tearing the car apart