Foxy Smith Posted April 19, 2007 Share Posted April 19, 2007 ’92 Swindon Vx with dry sump, bellhousing oiltank with co-axial hydraulic clutch slave. For the last few months and getting progressively worse I have been aware that when accelerating hard and engine revs just get over 5000rpm the hydraulic clutch appears to lose pressure. That’s to say the pedal drops away from my foot. There is no suggestion of the clutch itself slipping as the car continues to accelerate well but suddenly having no clutch when about to change up has resulted in a few near missed gear changes. I though I had the problem solved when I bled the system and found that the old fluid had a lot of small air bubbles present however despite having a nice firm clutch pedal it still droops above 5000 rpm. Perhaps some automotive Viagra is needed. I really can’t figure out what’s happening here. The fluid has to be going somewhere, yet there is no sign of leakage, fluid level in the reservoir is rock steady and below 5000rpm the clutch works perfectly. Anyone have any bright ideas? Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted April 19, 2007 Share Posted April 19, 2007 Vibration above 5000 rpm from clutch to release bearing to clutch piston causing leak from seals? Just a guess. Link to comment Share on other sites More sharing options...
Foxy Smith Posted April 19, 2007 Author Share Posted April 19, 2007 Alex, it's not a leak. Been there and done that with leaking seals!! Link to comment Share on other sites More sharing options...
Beelzebub Posted April 19, 2007 Share Posted April 19, 2007 [Theory]. Could the particular frequency of vibration at 5 K be causing cavitation / frothing of the hydraulic fluid. [/theory] Perhaps changing to a different type of fluid may help. On the other hand I could be talking 🙆🏻 D. Link to comment Share on other sites More sharing options...
Paul Gibb Posted April 19, 2007 Share Posted April 19, 2007 This could be caused by local vibration and would not necessarily require the seals to leak. The piston could move from its normal resting position, recoverable with a quick pump on the clutch after which pedal pressure would remain firm. Difficult at the end of long straights if you dont know whether the pedal is going to be there when changing down in extremis! Do try rebleeds/fluid changes etc but if the problem persists suspect vibration. L7 FUN Link to comment Share on other sites More sharing options...
Foxy Smith Posted July 5, 2007 Author Share Posted July 5, 2007 Thought I'd better do an update on this! Problem was solved by replacing the master cylinder. I still have not got around to dismantling the original but I'm assuming a seal problem.The original master cylinder was only about 4 years old, the previous one had been in service since '92 to the best of my knowlege. Link to comment Share on other sites More sharing options...
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