A hydraulic puzzle.

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tomsheppard
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Joined: 19 Dec 2002, 14:46
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A hydraulic puzzle.

Post by tomsheppard »

Car: BX.
Tail droops overnight if parked at normal height but
Nose droops if parked in highest position.
I guess that rules the doseur valve out as the cause of the problem.
Is this a rear strut leak or a height corrector problem? Any ideas welcome!
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AndersDK
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Post by AndersDK »

Tom ! Image Image
this is the usual mind bender on the standard hydropneumatic suspension [8D]
Let's take it step by step - makes it easier to argue against me [:I] :
1) The highest suspension setting is forced by the manual setting, which also forces the HC's constantly open.
2) As the HC's are constantly open from pressure supply to suspension cylinders, they also effectively connects all 4 wheel's suspension cylinders together by way of the suspension pressure lines.
3) The front of car is much heavier than the rear, meaning you have a higher counter-pressure in suspension spheres at front to keep up the front.
4) WHEN the car is parked in high setting, AND the accumulator sphere reserve pressure drops BELOW 100bar, the safety valve closes off the suspension from the main & brakes system. This leaves the 4 suspension cylinders & wheel spheres inter-connected - as the HC's are still forced open.
5) As the pressure drops further (by the rear brakes circuit leakage), then the front spheres acts as accumulator spheres for the rear suspension, effectively compensating and keeping up the rear, but the front slowly drops as the pressure here drains [;)]
6) If you wait long enough - the rear will also start sink [8)]
If not - you better have a look on the rear suspension arm bearings [8]
It still is the brake doseur teasing you [}:)]
So you better go overhauling the brake valve
tomsheppard
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Post by tomsheppard »

OK, I follow the logic and I think you are right. It is a Turbodiesel- oh Dear! The n/a car I could do the doseur in a couple of hours but I think the turbo one is going to be a little trickier!
I have not heard of anybody successfully overhauling a doseur (200,000Km) so I guess that I'll be spending a lot of money soon!
jeremy
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Post by jeremy »

If it takes alnight to sink there isn't really much wrong is there? BX of course have no anti-sink mechanism and also have large pumps so I don't see that there is any need to do anything at all, especially as the suggestion is that many of the new doseur valves don't seal brilliantly.
jeremy
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