Variation on an old topic SPHERES

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mike davies
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Variation on an old topic SPHERES

Postby mike davies » Mon Dec 24, 2001 12:24 am

Hi, what is my problem?.Symtoms:-engine running set in low mode,open acc. bleed valve one turn, whooshing noise evident. leave engine running for another few mins. then stop. Attempt to remove rear spheres and they undo ok. However there is PRESSURE evident and loss on LHM fluid. The only way to remove the spheres is to loosen the feed union pipe to each rear cylinder and wait for the pressure to cease and then remove spheres.What could be causing the pressure retention? <img src=icon_smile_shock.gif border=0 align=middle>The car is a 2.0 SX HDI estate with 6 spheres in total
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alan s
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Postby alan s » Mon Dec 24, 2001 3:22 am

Mike,
If the spheres are "blown" internally (ie) membrane ruptured, which is not all that uncommon, the LHM gets into the sphere and apparently into the cavity normally occupied by the nitrogen. The membrane is around 3mm thick so a small tear in it can act almost like a valve. When you release the sphere from the cylinder, the pressurised LHM in the upper cavity has a pressure above atmospheric, hence it is as though the system still has pressure in it as the LHM which has got into this upper section, pushed in by the hydraulic pump, then forces it's way back out through the ruptured part of the membrane and hence out of the damper hole. They then do a great impersonation of a water pistol as they can spray up to 20 feet, sometimes more when they are taken off and depending on how long they have been flat can hold a heck of a lot of LHM (overall capacity of spheres is either 400 or 500cc) which usually finds it's way all over the car if this is not expected.
It's a fairly common phenomena and one that explains why when a car blows a sphere, the level in the LHM falls dramatically and suddenly without ahowing any signs of external leaks and why at times the LHM will come from the overflow for no apparent reason. <img src=icon_smile_shock.gif border=0 align=middle>
Hope this explains the mystery <img src=icon_smile_big.gif border=0 align=middle>
Alan S
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