Interesting pressure regulator issue

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RobC
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Interesting pressure regulator issue

Post by RobC »

I have an interesting 'feature' of my pressure regulator / HP pump. TLDR it behaves differently on startup compared with after a run.

First off I'll say that there is plenty of LHM in the tank, and the HP pump belt is new and nice n tight.

So, on startup the car rises and low pressure light goes out. So far so good. But the pump continues to run constantly, as the PR clearly doesn't feel like it's sufficiently up to pressure to cut off the pump. If you blip revs to 1500 it sorts it, but then after a while sitting at idle when there'd usually be a pssht-click, it just reverts to the endless psssht of a PR not cutting in and a pump continually under load.

HOWEVER - once you've been for a spin, everything is fine - when back at idle the PR clicks in and out as normal.

So clearly there is something wrong somewhere that is then cured by the pump turning faster than idle speed for consistent & sustained amount of time. Air in the system from startup that's then cleared? A bout of citaerobics has no effect.

Perhaps the PR just needs the ball valve reseating. And maybe the pump has seen better days. But surely a weak pump would be weak whether or not you'd been for a run.

Any ever had similar?
1991 Citroen BX 16v
rutter123
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Re: Interesting pressure regulator issue

Post by rutter123 »

Knackered hp pump I reckon.
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Jaba
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Re: Interesting pressure regulator issue

Post by Jaba »

+1
But it might be worth giving that bearing valve behind the accumulator a tap. I have never had the need to do it myself but Jeremy, late of this parish, was always recommending it.
Have you done the pressure retention test - you know sitting on the bumper or raising the height lever and waiting for the suspension to lift having just switched the engine off. If this works then the PR is retaining its pressure.
How is the steering feel when starting from cold as this can be a sign of a weak pump too. Is the pickup filter clean.
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RobC
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Re: Interesting pressure regulator issue

Post by RobC »

Thanks for the replies. The car still rises at the back with engine off. I’m not convinced it’s the pump that’s the sole cause of this particular issue, because The power steering is great with no stiffness even at low revs, and the car doesn’t take too long to rise. And the issue goes away once you’ve been for a drive, whereas surely a weak pump would show weakness whenever, even after the cars been taken for a spin. However once the cars been out for a spin the issue goes away.

I’ll give the filters a good clean anyway, and double check for tightness of pipe clips etc.

Clearly it’s got to be one of either pump, PR, or LHM system and pipework. Not a fan of stabs in the dark though, hence being curious in case it was a ‘known’ problem with a ‘known’ cure
1991 Citroen BX 16v
den10111
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Re: Interesting pressure regulator issue

Post by den10111 »

Hello!
I am new to different Citroen tricks, but it seems like I have almost the same feature in my 19GT (with PAS).
HP pump works with rattle sound constantly (as I understand that means it works under load). When I rev engine a bit and rise the suspension there's a hissing starts to sound from a PR. No clicks, just continuous pssss.
But at idle this sound disappears.
Then after a minute or two this hissing gradually increases, starting with some gaps. And then I hear continuous hissing which stops when I turn steering wheel a bit.
All this time HP pump works constantly.
So... What could it be?
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Re: Interesting pressure regulator issue

Post by rutter123 »

A noisy or as you say rattly hp pump would usually denote that it's knackered and struggling to maintain pressure.
If everything is working as it should your pressure release valve should give a good audible click every 30-45 seconds.
A flat accumulator sphere can cause issues as well.
90 BX Tzd turbo 294k SORN undergoing major surgery
90 BX Tzd turbo estate 46k awaiting surgery
65 Peugeot Boxer Van the new workhorse
52 Toyota Rav4 180k Bulletproof Jap reliability