One for the hydraulics experts!!

[ghaddon1701]

Hi all,
Two questions. One is regarding the HP, the other regarding the brakes. I apologise in advance for my long questions. Writing isn't my strong point.

Question one.

When I purchased my BX about 18 months ago the HP pump was noisy. Like a chattery buzzing noise constantly. That changed in sound as the revs went up. As the revs got really high the sound was finally drowned out by the engine. It seemed to work ok so I left it. The power steering started to go heavy from time to time. So I decided to change the LHM and clean the filters. Came to prime the pump, it wouldn't! Had to hold the revs at about 3000 for 10 minutes and then the suspension gradually pumped up. Then after quite a while the steering lightened. Changing the fluid helped the steering for a while but didn't make the pump any quieter. So I purchased a reconditioned HP. Primed perfectly, no noise, well not at first. Now it is as noisy as the pump I replaced. It was replaced just before Christmas. Seems to be a bit quieter when its been driven for a long time. Sometimes you can barely hear it. Any ideas anyone?

Question two.

How are the brakes on a BX supposed to feel? For instance. Are they supposed to be as sharp as CX brakes? Breath on the pedal and you stop? Or a Xantia even. When I move my Fathers Xantia off the drive to get my car out the brakes are tremendously sharp at slow speeds. On my BX they just aren't really sharp at all. I have recently replaced front pads and discs. Rear pads, discs and calipers. Changing the rear brakes did make quite a big difference. You can feel the back brakes working. The back end squats. It didn't before. But still the brakes aren't very sharp. All four wheels will lock but you have to push the pedal quite hard for that to happen.

Hope I have made sense.

Regards Graham

[citronut]

the pump noise sound like either there is not enough citro blood bin the tank or the pump is sucking air from maybe a crack/slit in the main rubber sucktion feed pipe to the pump, usualy near/next to/as it leaves the tank


the brake sound fine unless you feel a pattering under your foot,


i would say the CX and XANT have air in there brake circuit's,

as the first presure of any hydraulic citroen brake pedel should be gentle/normal braking,

and the second presure locking everything up (emergency stop),

also if every suspension and braking is working correctly the rear should sit down on braking,


regards malcolm

[ghaddon1701]

Hi,
Regarding the pump noise:

Plenty of LHM in the tank. No splits in the pipe. It just seems strange it is noisy but it appears to work perfectly fine.

And the brakes:

The Xantia brakes are working fine. It is a late Xantia with the spring between the pedal and the Doseur rather than a metal rod. They are only very sharp at parking speeds during normal driving they behave similarly to my BX. Also I know there is supposed to be between 0.1 and 1.0mm of play between the pedal and the metal rod that goes to the Doseur. But is there supposed to be play between the rod and where it touches the Doseur?

Regards Graham

[MULLEY]

Is the pump belt very tight? if its slack it might cause the noise? or perhaps its just old & had deterorated and is causing vibration even though its on tight. If its not that, then i guess the pump is worn out & thats where the din is coming from

[ghaddon1701]

When I replaced the pump I changed the belt aswell. Had to re-tighten after a few hundred miles because it started to slip. No such issues now though. I will have to see what Pleiades thoughts are. Thanks for your comments.

[B-Hive]

I too have a noisy pump that I'm resisting swapping out for the very reason that you mention. Being that the cause may well be something else.

So I am going to swap out the accumulator sphere as, if they are flat, there is no damper between the pump and the regulator and can create a clatter.

Odd thing is though the accumulator sphere seems to pass most of the other tests.

It seems that noisy pumps is a feature of the BX as apparently the pumps have being built down to a price. Mine too works quite well and pumps very efficiently but the din is quite insane.

[Linegeist]

I disagree. Sorry. When properly assembled and working correctly, the Citroen HP pump is almost silent in operation. The suspension system isn't a bad design for something that's quite ancient technology in automotive terms.

A word of caution here - getting a reconditioned pump is no guarantee of getting a silent one. I went through 3 with Pleiades - the first one would randomly drop out of circuit leading to serious all-bran moments on bends and roundabouts, the second one was noisier than the one it was destined to replace, and sounded as if it was trying to climb out of it's mountings to snot the LHM tank. The third one was the quietest of the three, but still occasionally emits a woodpecker sound at medium revs. I cut my losses and left it in situ.

When I stripped the 'spare' pump (the noisy one that had been reconditioned) I discovered that the valve discs that control the LHM flow in the pumping element had been 'reconditioned' - possibly by use of a grinding compound on some kind of flat surface. Three of them had deep scoring in their faces that was, presumably, setting up the knocking noises I could hear when the pump was running under system pressure.

I gather these valve discs are no longer available new so I can see why the pump's reconditioner tried to recycle the old parts. Just that, in my case, it was unsuccessful.

Twice!

Goodness knows what was wrong with the one that dumped its pressure when driving. I dread to think............. So, from past experience, my advice is, if you can't strip the pump yourself or get a known good second hand one, test the reconditioned replacement carefully before you entrust your life with it.

[B-Hive]

I disagree. Sorry. When properly assembled and working correctly, the Citroën HP pump is almost silent in operation.

I'm sure brand new or perfectly rebuilt they are almost silent, I guess my point was the BX pump's lesser build quality lends itself to earlier noisy operation and difficulty in re-building properly.

It really isnt a prevalent issue with D's G's or C's.

[citronut]

it has been known for one or more of the pistons in the pump to become stuck,

this too can cause the pump clatters,


regards malcolm