XM hydraulics help!

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nino
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XM hydraulics help!

Post by nino »

Hi, i see this forum is very helpful so i'd like get some of that too :)
Here it goes:
I own a XM V6 auto i got recently.
A few weeks back i was changing a flat tire which went ok, but afterwards when i started the car i got the stop light and "warning - brake pressure loss" message. No rising, no clicking, no brakes. It didn't go away until i traveled a couple of meters and gently hit the pavement (which rocked the car a little). That seems to have goten the pump working again.
But now the problem is as follows:
- Fast rising, fast sinking.
- Excessive clicking (around 5 sec when idling).
- As i accelerate from stopping towards the second gear the clicking becomes faster and faster the faster i go, until it finaly slows down a i gather some speed.
- Also as expected using the power steering and the brakes with no velocity makes the clicking go incredibly fast at times (up to 1/2 a sec)
Thanks in advance
jeremy
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Post by jeremy »

Not sure it answers all your symptoms but the rapid clicking points to the accumulator having failed. I expect this is on the end of the regulator and is a simple sphere without a damper.
2 tests - get the car to normal height and sit in the boot. Car should drop and after 30 secs or so return to its original height powered by the accumulator. If it doesn't the accumulator has failed. The other is to raise it to full height and see if it slows as the suspension spheres will function like 4 accumulators while the height correctors are open.
My guess is that some of the other problems are actually due to the height correctors and linkages being stiff and a good grease may well solve the problem.
jeremy
nino
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Post by nino »

The accumulator sphere?
Being located upfront?
FrenchLeave
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Post by FrenchLeave »

Yes, up front and low down (underneath). Jeremy's "sitting in the boot" test should of course be done after you've turned the engine off.
What year is your V6? This is important because there are major differences in the suspension between early and late models - like Hydractive 1 or 2, anti sink valves etc..
bxbodger
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Post by bxbodger »

A further test for a dead accumulator sphere is to put your foot repeatedly on the brake- if you hear a click with every application then thats another sign its gone flat.
FrenchLeave
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Post by FrenchLeave »

Have you checked the fluid level is OK?
Niek
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Post by Niek »

If your acc sphere is that gone you should also get a pulsating/vibration from the brake pedal when applying the brakes. (it did this on our Bx, acc replacement solved this.
Fast rising is good :)
Fast sinking could be acc sphere related
nino
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Post by nino »

It's a 1991.
What is the best way to confim the acc sphere is gone?
jeremy
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Post by jeremy »

To see if the accumulator has failed try the tests suggested above!
jeremy
nino
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Post by nino »

Ok, did the tests.
At maximum height i get a neglectable slowdown in clicking (still clicks alot)
With the engine off, if i sit on the rear end it rises back again instantly a soon as i let it go.
FrenchLeave
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Post by FrenchLeave »

Nino, I think you misunderstood Jeremy's instructions. It's supposed to raise up with you still sitting in the boot. The idea is that your extra weight causes the rear end to sink, the height corrector senses that the back of the car is too low and opens the supply side to the suspension to raise it back to the correct height. With the engine stopped, this supply should be provided by the accumulator. If the car doesn't rise to its correct level under that circumstance is proof that the accumulator is duff. (Sorry Jeremy for pinching your post).
nino
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Post by nino »

Yes, no rising in the back while under weight
bxbodger
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Post by bxbodger »

Try the brake application test I mentioned above for further confirmation! Do it with the engine running.
jeremy
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Post by jeremy »

I would have expected the cycling frequency to have slowed when the car was raised to full height.
Clearly the accumulator is not holding anything. Generally this means that the sphere is flat but as the frequency didn't slow when the car was raised it suggests an internal leakage somewhere, probably from the regulator non-return valve. This is found on the face under the sphere on the regulator and is simply a ball bearing retained by a metal plate and a bolt. The bearing can be re-seated by striking it smartly with a brass punch and re-assembing. Steel must NOT be used as it will put a flat on the ball. My own BX went fron cycling every 8 seconds or so to so long that I can't be bothered to measure it and I did it about 3 years ago.
Before doing that job its worth having a look in the reservoir to seee if its likely that air is getting into the system (milky looking in places?) (The system doesn't have seals and relies on surface tension. Air doesn't have surface tension and so the valves and things can act like an air sieve if you get what I mean.)
jeremy
nino
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Post by nino »

I'll haul ass to the garage asap.
Just out of curiosity, how does the system function (in the degraded way it does) then there is no pressure in te acc sphere?
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