XM hydraulics help!

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nino
Posts: 13
Joined: 11 Jul 2005, 16:29

XM hydraulics help!

Post by nino » 11 Jul 2005, 16:53

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
Posts: 3959
Joined: 20 Oct 2002, 16:00

Post by jeremy » 11 Jul 2005, 17:26

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
Posts: 13
Joined: 11 Jul 2005, 16:29

Post by nino » 11 Jul 2005, 19:52

The accumulator sphere?
Being located upfront?

FrenchLeave
Posts: 359
Joined: 18 Jan 2005, 22:47

Post by FrenchLeave » 11 Jul 2005, 21:16

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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Joined: 23 May 2003, 03:34
x 1

Post by bxbodger » 11 Jul 2005, 21:30

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
Posts: 359
Joined: 18 Jan 2005, 22:47

Post by FrenchLeave » 11 Jul 2005, 22:19

Have you checked the fluid level is OK?

Niek
Posts: 135
Joined: 18 Sep 2002, 18:09

Post by Niek » 11 Jul 2005, 23:33

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
Posts: 13
Joined: 11 Jul 2005, 16:29

Post by nino » 12 Jul 2005, 01:08

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

jeremy
Posts: 3959
Joined: 20 Oct 2002, 16:00

Post by jeremy » 12 Jul 2005, 01:14

To see if the accumulator has failed try the tests suggested above!
jeremy

nino
Posts: 13
Joined: 11 Jul 2005, 16:29

Post by nino » 12 Jul 2005, 23:35

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
Posts: 359
Joined: 18 Jan 2005, 22:47

Post by FrenchLeave » 13 Jul 2005, 00:10

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
Posts: 13
Joined: 11 Jul 2005, 16:29

Post by nino » 13 Jul 2005, 03:44

Yes, no rising in the back while under weight

bxbodger
Posts: 1455
Joined: 23 May 2003, 03:34
x 1

Post by bxbodger » 13 Jul 2005, 05:12

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

jeremy
Posts: 3959
Joined: 20 Oct 2002, 16:00

Post by jeremy » 13 Jul 2005, 05:16

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
Posts: 13
Joined: 11 Jul 2005, 16:29

Post by nino » 14 Jul 2005, 01:07

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?