clutch slave cylinder leak

[chicagojeff]

I recently had the engine rebuilt on my S3 twink, and had a new clutch disc put in. A day later, all the clutch fluid dumped out through the slave cylinder. Does anyone have a rec for determining how to tell if the piston is over-extended? In other words, it may just be that the adjustment isnt right, and so the seal leaked. Tighten or loosen? That would be best case. Worse case is a failed seal, and worst case is a really pitted and shot slave cylinder. Any thoughts? thanks. Jeff

[types26/36]

Jeff,
My thoughts on the subject would be: because you had a new clutch plate the piston in the slave is now working in a different position in its bore, if that part of the slave bore has not been used in a long time it may have pitted and now the seal is running over it and the seal became damaged.

[chicagojeff]

brian, thanks. that seems like the most reasonable theory. I was hoping that maybe the piston arm is just not adjusted right, but I think that would have meant leaking pretty much right away, like immediately after we got the car back running. The leaking didn't start till after I had taken it on it's first real drive of about 25 miles during which I used the clutch alot. I probably wore down the seal or tore it on a pitted surface so that the full blown leak developed.

I was just going to replace the seal, but now I fear that wont do the trick...How hard is the job to replcae the slave cylinder? Can't be too tricky?

[types26/36]

I was hoping that maybe the piston arm is just not adjusted right,
I was just going to replace the seal, but now I fear that wont do the trick...How hard is the job to replcae the slave cylinder? Can't be too tricky?

The adjustment consists of making sure there is a little "free play" on the push rod when pulling the clutch arm against the spring, there is a measurment but if you have a little play it should be fine.
The slave cyl. can be a problem to remove, it is aluminium and can "sieze" in the bellhousing which is cast iron, the different materials dont react together to well.
The slave cyl. is held in place with a circlip (snap ring?) which can prove difficult to get off.
Generally you cannot get the slave cylinder off with the exhaust manifold in place but this can depend on the type of exhaust manifold.
Although its a bit of a bodge, it is possible to replace the piston seal without removeing the slave cylinder, the problem here is you cannot get at the slave to clean the bore very well..........well I said it was a bodge!

[ElliottN]

Jeff, I have recently replaced my clutch slave cylinder after an identical experience and I am now on intimate terms with the job. In my case the new slave cylinder was about AUS$100 (US$75) so I went for a complete replacement (re-using only the original pushrod).

It is EXTREMELY tight work with the standard setup but I unbolted the exhaust headers (at the head) and then loosened the exhaust bracket at the gearbox - allowing me to drop the headers about 30 mm - which then gave me adequate clearance to work on the slave cylinder (I have fairly big hands). Note however my headers are bolted on with cap-head screws and are not on studs. I have read of people doing it without creating clearance from the exhaust and I don't know how they did it - maybe they have hands the size of a 5 year old and some very custom shaped wrenches!

In my case the slave had become a very loose fit (part of the problem) so it was very easily removed. You only need a pair of circlip pliers and the appropriate wrenches and it's a straight forward job. If you do lower the headers, make sure to bleed the system and adjust the pushrod and check clutch pedal takeup before re-installing them as I found it impractical to get wrenches on to the pushrod locking nuts and bleed valve once the exhaust was back in it's normal place.

[chicagojeff]

i guess i'll see tomorrow how much clearance I have...any thoughts on replacing the master cylinder at the same time? Conventional wisdom says I might as well do both, but there havent been any problems with the master. I suppose that is pretty easy to swap out though. thanks, Jeff

[reb53]

If you think the slave is difficult wait until you try the master......
This is probably a case of, "if it ain't broke don't fix it", especially as it isn't a safety issue.

Ralph
71 Sprint.

[collins_dan]

I replaced the seals in my '70 S4's slave cylinder last fall and the master cylinder failed almost immediately. I also didn't have too much trouble getting either out from the car. It takes time and is frustraing as its awkward, but my header was not in the way and nothing had seized. (Well lubricated from the oil that flows freely from the engine.) If I was to do it again, I would not only replace the seals, (which probably cost a total of $40), but probably just go ahead and replace the cylinders as well. My recollection is that from Bean they were in the $50-70 range each and while not terribly pitted inside, I'd don't think that it will take too long before they chew through these seals. Dan