My Citroen XM 3.0 PR-Vestige

[Dean]

The car is not at ride height, it had sunk by the time i had investigated that evening but yes, i still think there is a massive chance the regulator has jammed (odd) or there is a blockage somewhere in that area.

D

[White Exec]

Assuming you can engine drive the pump at idle speeds:
Put the car on Lowest.
Start the engine and let it idle.
What is the Low Pressure Warning telling you? This is crucial to understanding what's going on.

[Dean]

.......................im confused!

I got the old belt out and looped it over the pulley, there is no tensioner bolt fitted so the pump cradle is just sat on its single pivot bolt, started the car and the light went straight out as usual and the car came up to normal ride height.
The regulator cuts in and the belt slips a bit, i can see the pump pulley jerking round, i presume as each piston comes to the top of its compression stroke but then the pump is just hanging there by one bolt so it kind of will, the belt isn't tensioned at all. regulator cuts out and the belt grips fine.

Turned the car off and there was no hissing, i kind of have no choice but to get another belt and try again, i will get a pair of belts though and keep a spare, just going to hoover all the rubber dust out of the engine bay now. i will have to see how it goes..................

D

[Dieselman]

Maybe it's becasue the belt was toot ight it wore the edges so started overheating and slipping, which then finished it off quickly.

[Dean]

hopefully, or it could be an intermittent issue, or it could be the extra pressure i run doesn't agree with the higher geared belt drive ratio of the V6 v the reduction gearing of the belt drive on the 2.0.

It could be the pump drive setup is just running on the ragged edge of what the design can cope with and a ribbed belt conversion or double V belt setup would be better?

D

[White Exec]

Sounds like it's now working 'on the edge' of belt tolerance.
Possible to check what pressure the system is running at, and reset it to something like standard?
At least you'd then know what pressure the regulator was kicking out, and whether it is stable, or a regulator fault.
Why did you originally increase it, and what to, Dean?

Getting there...

[Dean]

i would have to look back on the forum but i think i upped cut out by 10bar? i will need to check that was this car and not the Activa though.

I upped it because it was too low from spec and gave it that little extra and increased the acc sphere size and pressure to increase cycling times and give a greater store of pressurised fluid.

If Matthew says the belts on these are problematic it could be this setup just takes the strain on the pump too high.

D

[Dean]

I am running 150bar cut in, 180bar cut out.

D

[xmexclusive]

Looking through the Citroen manual gives the reasons for the early XM hydraulic pump changes.

On pumps up to RPN 5208 the main bronze bearing is a smaller size and prone to damage particularly if belts are over tight.
This wear can lead to air ingress between shaft and bearing causing intermittent hydraulic lock up of the system.
Symptoms can be low pressure light and loss of power steering at high engine speeds.
Larger bearings were used from this date.

The increases made in pump pulley diameter (diesel and petrol) were to prevent excessive pump spindle speed at very high engine revs.
It reduced the pump output a bit but mainly reduced the high load on the main bearing.

I think earlier pumps with small pulleys also may well indicate a weak main bearing in those pumps.
Seems that belt tension needs careful set up rather than wound as tight as possible.

John

[citroenxm]

Now i wondered why i had v6 pumps with two sizez of pullys

I fitted a larger size pully pump to my 24v once and it would not perform.. it was when i was stuck for a belt and tried to use the larger pully pump to take the slack up on a too bigger belt. . No good.. so reverted back to smaller pully and had to wait for a smaller belt.. after fitting it all again issues resolved..