xm mk2 rear hight

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nino1
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xm mk2 rear hight

Post by nino1 »

Hi, i have a question regarding my '98 xm sedan.

I seem to be having a problem in the rear.
While overall hydraulics seem to be fine the rear seems to be sometimes positioned too high combined with an occasional hard ride.
It seems to ride to high than drops in one swift motion and then rises back to the previous hight within some 5 sec or so.
This seems to happen more often after i start up.
After the initial drop i feel the soft ride kicking in and it tends to stay that way for a while.

Ideas?

Tnx.
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AndersDK
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Post by AndersDK »

Clear indication of a sticking HC mechanism. Even the HC itself sticking.
When its too high it is stiffer. So its not just a feeling, its a fact.

Its overhaul time :wink:
Anders (DK) - '90 BX16Image
nino1
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Post by nino1 »

Thought as much.
Is it possible the HC is ok, but the linkages are sticking?
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AndersDK
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Post by AndersDK »

The linkages are pretty simple on an XM.
You have a long steel rod curved in one end where connected to the ARB. This is the flexible part of the linkage.
In the other end its got a simple rod-in-a-hole pivot where the rotating movement is transferred to the HC by a short plastic arm.
Check that this plastic arm is still located on its ballhooks.
The plastic link may have worn too wide in its ballcups to keep fit, then you need a new plastic link arm.

96 174 036 CORRECTION LINK
5273 12 SEAL WASHER
These parts are very cheap.

I was not aware in my first answer, that the series 2 XM has this plastic link arm. This link arm is known to be the problem in most cases, and its about right it satrts playing up on your '98 XM. The washer is a felt washer that should be wetted in grease to keep the ball link lubed and protected against the grease drying out. The ballcup on the new plastic link arm should have a tiny dap of grease - any kind.
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Post by RichardW »

I'm not so sure this is a HC problem. This is an XM with hydractive don't forget, which rather complicates things! What is happening is that the rear hydractive unit is sticking, and there is a pressure imbalance between the wheel spheres and the centre sphere. When the HA valve opens the pressure from the wheel spheres is dumped into the low pressure HA sphere causing the rear to drop. The HC then takes over and corrects the height. My hydractive Xantia does exactly this, and has done since I have had it (2 .5 years 60k miles) - it also has the sunken rear end when stopped that seems so common on HA cars. Never figured out why, but I suspect that the diode is pretty dead in the rear HA valve. Possible it has been less bad though since I got the rear HC lubed up. So... how to proceed? Well, first clean and lube the HC, then fit the supplementary diodes into the HA wires (see recent posts on here about this), and see how it goes. I guess new rear spheres might help too - I think mine is running on the original 10 year / 115k mile old ones.... :oops:
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nino1
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Post by nino1 »

Tnx.


From what i see HC sticking is a common vanilla failure, but mine was replaced aprox 1 year ago, and the movement seems to be unobstructed.
Also movement from top to bottom is smooth.
The rear does exactly what you Richard said.
I'm guessing this would mean the HA in general is malfunctioning in a sense the rear (maybe even the front?) electrovalve is not operating (sticking?).
Richard, from what you say i deduce it's not directly implied the center sphere (rear or both) is flat?
Also are HA computer or general connections a possible issue?
I also hear there is a midcar HA electronics connector when going to the rear.
nino1
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Post by nino1 »

Not to forget, slopes seem to trigger this behavior more often.
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AndersDK
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Post by AndersDK »

The HA system can only do 2 things : connect - or disconnect - the extra axle sphere valve. Its quite easy to check.
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nino1
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Post by nino1 »

I've read about stationary techniques.
Any way to test it while driving?
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AndersDK
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Post by AndersDK »

If it works stationary, it still works during drive :idea:

If you feel it doesnt work during drive only, then its not the valves at fault, but a sensor or the ECU at fault.
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Post by nino1 »

Ok tnx.

The test is to do a bouncing test just after turning the engine off, and them one more after the bzzzzzt sound :) (doors closed i believe)?
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