So I went to drive my '87 740T today which had been sitting for about a week and I stepped on the clutch and felt no resistance. Looked under the hood and the slave cylinder is fully extended holding the clutch disengaged, fluid resivoir is a bit low as well. I have a second car but I need to fix this ASAP, what should I look for? The car has 255k on it and has never had a hydraulic problem that I'm aware of.
I'd try loosening the bleed nipple to see if the system is pressurised. If it is, then the fluid is not being allowed back into the reservoir, so I'd suspect the master cylinder - piston not returning properly.
The mystery is how the slave became extended while it just sat there. It's a pretty powerful spring it pushes against. Did the clutch get operated before you found there was no resistance?
In my experience, replacing the rubber seals in the master cylinder is rarely worth while - get a complete new cylinder; they are not so much more expensive than a seals kit, and the seals kit may not do the job properly anyway.
Well I had a look at it tonight, seems the master cylinder is fine, what happened is the slave cylinder got extended far enough that the rubber seal on the piston got caught against the opening of the bore, how it got extended that far I'm not really sure, but I reasembled it with the damaged seal and verified proper clutch function. Ordered a new slave cylinder tonight so hopefully installing that will fix it.
It's strange that it works normally now. I was thinking it may possibly indicate that some part of the clutch mechanism is worn beyond it's sevice limit. Clutch plate wear should shorten the travel of the slave, but if the thrust bearing or spring plate or actuating arm are worn or damaged it could allow the slave to extend too far.
On mine I found the plastic end of the slave actuator had worn there it locates into the hole in the clutch arm. My cheap solution was to fit an old nut in the cup of the piston to make the rod longer. Lasted for years.
Stuart.
I should have mentioned the clutch assembly and thrust bearing were replaced about 2k miles ago, the rod will extend further with a fresh clutch than a worn one, still I find it odd that it did this. It must have happened when I pressed the clutch to place it in gear after parking it.
disengaged,
I'll try that, I'm not sure what bits the new cylinder comes with.
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