Club XM Forum > Whow

Michael P

August 06, 2006 07:27 pm

Hi

Just to say that I have changed my hydraulic pump yesterday for a new and reconditioned one from Pleiades. Yes, was a bit costly but there you go.
It eliminated all sorts of oddities with the car and it behaves normally now. I am surprised how little the pressure regulator works now.
I have of course also changed the LHM and the accumulator sphere. That was a mornings work. The silly design of the pump cradle (which couldn't be removed) meant that I had to remove the electronics box as well to get it out. Pain.

And now the standard symptom after hydraulic part renewal: It doesn't sink. Well it will take about a week or so until it will behave normally. I think I have posted this here before or on the BX list, so far nobody was able to give me any credible explanation for this behaviour.

Sorry for the inconveninece reading but I have hit the wrong key compbination and I don't know how to get back

Michael

jorgy9

August 06, 2006 09:51 pm

QUOTE (Michael P @ Aug 6 2006, 18:27 PM)

And now the standard symptom after hydraulic part renewal: It doesn't sink. Well it will take about a week or so until it will behave normally.

I'm after that issue, while trying to cure a hard front suspension (electronics are OK).

I have had symptoms that tell me that the air being trapped in the hydraulic pipes (during working or changing elements on the system) plays a role in the symptom you describe. My story is long, u can find the thread in this forum if u want.

It seems that air is being traped, specially in the rear brakes piping (I can't explain why specially at the rear, I speak by experience). If it's in, the car sinks rather slowly. After bleeding all 4 brakes on mine, the rear sinks fast, in about an hour or so. Front is still slower. To cut a long story short, I suspect there is something going on with the brake valve and the presence, or not, of air in the rear brakes. I believe XMs sink at the rear because they leak through a leaky brake valve (rear suspension is connected to that to adjust rear braking force).

I will test this sometime soon by blocking this connection with a simple screw (3.5mm), drive the car round the corner to pressurise it again up to normal (with effectively no rear brakes), then park as always. It should sink slowly, I expect.

rgrds
George

jorgy9

August 06, 2006 10:02 pm

Of course, I forgot, you should bleed the brakes after having had the hydraulic circuit opened for any reason. As I said air is being traped specially in the rear brakes circuitry. I can tell how much air there is in mine by the way it behaves on braking: if it lifts the tail too much, it's time for a bleeding. This behaviour is effectively the result of the rear brakes not braking. A bled XM normally brakes absolutely flat -only the front can be felt to compress a bit, normal, like on any car-.

George

Michael P

August 15, 2006 07:34 am

Absolutely correct, the tail goes up and down, jsut by sitting onthe brake as well. Iknow I need to do it but as the neighbours had a big party that was a little delayed. THe annoying thing is I did that several times before and the air came back. I don't know where from. I have new LHM now and I hope it will be mroe stable now. The worst offenders in this matter so far were BXs.

Thanks

Michael

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