My Citroen XM 3.0 PR-Vestige

[Dean]

The belt size is correct, actually it's probably too short as i had to crank it on and take the pump off to remove it, the other belt was ok but kept slipping, every time i tightened it, it would slip and get chewed away and so on until i ran out of adjustment.

I broke out my usual emergency drill setup but the pump is just too stiff to turn when under load and slips, i could not raise the car one bit.

Undone the 12mm pressure relief bolt and the pump would turn reasonably freely but again i could not turn it at speed as it just got too hard to turn and the belt would slip and start to smoke.

what could happen gradually to increase resistance to the point where it would suddenly just strip a tight belt off, the only way to find out would be to start with the regulator, strip it and make sure it is operating correctly, or possibly just check the output pressure of the regulator to see if there is a clue there.

D

[White Exec]

It must either be regulator fault (or unusual hydraulic blockage) as you say, or else the pump just won't operate at higher revs - perhaps internal damage or bearing wear, which won't allow high revs - quite possible if belt has been far too tight.

If you undo the pressure relief bolt by maximum allowed, the pump should only be sending fluid back to the reservoir, which should allow the pump to spin up normally. Presume pump is single output: try letting the pump deliver freely back to the reservoir with a bit of clear tubing, maybe, to eliminate the regulator altogether.

After it's sorted, is there a possibility of a twin-belt or grooved belt conversion, for what looks like a marginal arrangement. Remember Russ complaining about similar a while ago?

[Dean]

Yes Russ did tell me when I ate the first belt but this just seems too extream. I have noticed that when the regulator opens you could feel the load the pump places on the engine, now this was kind of true on the 2.0i but it seemed more pronounced on the V6 engine and i would expect the higher output engine to not show this parasitic loss as much as it has.

Today this belt was tight as i tightened it again last night, then within 40 miles it just shredded the belt. It's a shame the hydraulics are a right bugger to get to on the V6 lol

D

[Dieselman]

Are you acquiring the correct type of V belt. A belt not fitting the pulley will wear quickly.

[MTXM]

If the belt and adjustment are correct it has to be a restriction or other issue with the pump that is causing the wear surely! Just out of interest do you have the early or later design pump Dean and is there another available to try? Regards, Matthew T.

[White Exec]

That's why I'm suggesting running the pump with no hydraulic load - to check it will deliver good flow, and rev freely.
You need to start with an unloaded pump, and then work onwards.

Interesting you say it won't raise the car at all.
Any steering or brake assistance?
Is there ever a Low Pressure warning from the dash?
If no low pressure warning, possible that the pressure is too high - for which you'd get no warning/alert.

Pressure regulator allows excess pressure (unwanted pump output) to be redirected to the reservoir, by lifting the regulator valve/spring. Maybe jammed.

Not sure whether you have a high pressure gauge. Could be screwed into the system pressure warning switch location, on the security valve, maybe.

[Dean]

If the belt and adjustment are correct it has to be a restriction or other issue with the pump that is causing the wear surely! Just out of interest do you have the early or later design pump Dean and is there another available to try? Regards, Matthew T.

It is the later pump with the larger pulley Matthew, i have a good 2.0i pump that will work but it will run to slow due to the larger pulley and the suction hose fitting is clocked wrong and needs turning 90 degrees to fit the V6.

Will, i believe i have the right belt, it's the shorter one im running for the earlier style pump but previously i had the longer one which would be correct for the later style pump i have, both have been Killed pretty quick.

Chris, i did run it with no load, 12mm relief bolt fully open and it was free enough but still hard work to run at speed. I could not get the car to lift using the drill but then it is hard work usually anyway with this method, it would build pressure and then just start to slip the belt and smoke, the car didn't move, when i last ran it she came up fine before it ate the belt.

D

[White Exec]

Not sure how hard it is to run up (with a drill) an unloaded pump - never done it.
Could you try drill-spinning your spare pump to make a comparison?
They don't need to go very fast, do they - even at engine idle, they should pressurise and pump up the car.

If your preferred pump is stiff(er), then maybe that's an issue.

What is the pressure warning display doing?
Pressure warning switch is downstream of the regulator, and should be telling you something.

[Dieselman]

Theoretically the only excess load can come from the regulator being jammed in the presssure building phase, or jammed pump. I doubt the pump is jammed, otherwise the nose seal would be leaking.

If the pump is producing pressure the car lifts, if the regulator is returning fluid the pump has very little resistance. It sounds as though the pump is being hydraulically locked as a result of the regulator continuing to feed the hydraulic circuit, which as the car is at ride height doesn't need fluid, so the fluid blocks against the height corrector valves and the pressure stalls the pump.

[MTXM]

That does sound like a reasonable possible diagnosis of the problem Will and hopefully further investigations by Dean shall confirm! Regards, Matthew T.