Is this normal? (Xantia suspension)

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allmond
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Is this normal? (Xantia suspension)

Postby allmond » Sat Aug 24, 2002 7:57 pm

I have a late 1998 Xantia 2 litre petrol Exclusive with Hydractive 2.
If I switch off the engine, get out of the car, and shut the door I can hear a faint buzzing sound. After about 30 seconds, there is a click and the buzzing stops. I assume this is the Hydractive switching from soft mode to hard mode.
If I bounce on the car, particularly the rear, while the buzz sounds, there is lots of travel on the suspension. As soon as the buzzing stops, everything is rock hard, as if the suspension spheres are shot.
I suspect a sphere somewhere on the car has gone, as I suddenly had to put about half a litre of LHM in the tank one day. Since then, no further losses. I have no other symptoms than the one described above.
Do all Hydractive 2 Xantia's do the same? (Lots of Xantia owners out in their drives bouncing on their cars. What a picture!!)
Am I looking for a problem that doesn't exist? If so, where did my LHM go?
Is there a way to find out if a sphere is shot or not, other than replacing them one at a time? Should a good one, and therefore not full of oil, have a certain weight? (I appreciate they can be low on pressure and therefore not fill with oil, but will fill if the diaphragm goes.) How can I tell? Any ideas?
Thanks in anticipation. <img src=icon_smile_question.gif border=0 align=middle>
Jamie
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JohnW
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Postby JohnW » Sun Aug 25, 2002 10:13 am

Now that is a GOOD idea.
I'd not thought of it, but as the nitrogen slowly diffuses away, the oil volume should increase as you say. For each sphere size, there should be a relationship between gas pressure and weight.
We need curves on a graph sheet or some clever polynomial.
I'll be really interested to see if anyone comes up with this - generally not hard to weigh things quite accurately with modern scales that use a sensor not a spring.
Cheers
JohnW
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allmond
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Postby allmond » Sun Aug 25, 2002 1:51 pm

Thinking it through further, though, as soon as everything returns to atmospheric pressure, which it would have to do to remove the sphere to weigh it, the oil would be expelled so long as the gas in the sphere is above one bar.
If that's correct, weighing would only work for totally flat spheres.
Anyone have any other ideas?
Jamie
Edited by - allmond on 25 Aug 2002 09:23:05
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Dave Burns
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Postby Dave Burns » Sun Aug 25, 2002 6:52 pm

Hmmm, yes there is a way of testing sphere's if you have a knowledge of metalworking and access to machinery.
What you would need is a rear suspension cylinder from a Xantia or BX and an oil pressure gauge capable of a few bars higher pressure than the sphere's you want to test, so about 75 bars would cover most Cit's.
The pressure gauge would be screwed into the cylinder at the point normally occupied by the high pressure feed pipe.
The cylinder would be rigged such that a hand wheel and screw could be used to drive its piston.
The cylinder would need sufficient oil in it any any air excluded and the sphere screwed on as normal.
How it would work.
As the screw is turned driving the piston forward, the pressure within the cylinder would rise rapidly as indicated by the gauge.
When the oil pressure in the cylinder has risen equal to the gas pressure in the sphere, it therefore follows that oil will then be forced in to the sphere as the pressure continues to rise.
But because of the compressable volume within the sphere, the gauge will display a much slower rate of increase in pressure even though the piston is still being driven at the same speed.
This transition point should be easily visible via the gauge and the pressure pointed to at that exact moment will be the gas pressure within the sphere.
I may knock one up at work sometime and test the theory, at times like this I wish I hadn't flogged my lathe and tackle.
Can anyone see a flaw in the Idea before I go and find it half way through making it.
Dave
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spanners
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Postby spanners » Tue Sep 10, 2002 4:36 am

THE NOISE YOU HEAR IS QUITE NORMAL IF THE CAR HAS ANTI SINK IT IS DESIGNED TO STOP THE CAR DROPPING WHEN LEFT SO WHEN YOU RETURN IT IS EASIER TO GET IN IT WILL ONLY GO SOFT AGAIN WHEN YOU START ENGINE THIS ALLOWS PUMP PRESSURE TO FLOW. THERE IS A SPHERE TESTER THAT ANDYSPARES SELL BUT IT IS EXPENSIVE. DUFF SPHERES WILL ALWAYS FEEL HEAVIER AND USUALLY A DUFF SPHERE WHEN TAKEN OFF WILL SPURT OUT FLUID AT GREAT PRESSURE.
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