Clutch slave cylinder failure-useful lessons
 

Hi-I was changing/flushing my 4 year old brake fluid (yes, I know) and then I thought should I change my clutch fluid also, as its on the same line in a 1999 s40 anyway.
I realized that it had not been done since I got the car, so I think maybe 8 years minimum that the fluid was in there. So I changed it and splat went the seal...

Some has contaminated the clutch as I have some take-up judder now, but hopefully I will get away with that.

Anyway, looked online, but it was really hard to find a replacement cylinder..however the rebuild kits are easily available on ebay, for about £8-9. The kit contains the bellows, the main seal and a new bleed nipple cap.

Shift some of the intake trunking and then you can find the cylinder...dismantling revealed hideous vileness inside, so I had to wash it out with detergent, then dry it, then flush with brake fluid and then soak for a while in the fluid. One thing I noticed was that the spring inside the cylinder was really nastily dirty, so I had to really clean that to make sure no crap got into the rebuild. Then fitting the new seal..it is clear which way that goes as the fluid pushes on the back of seal and expands it into the bore. The seal is a clever design..the edge that expands is wider than the rest of the seal, so it has a great deal of wear capacity in there, so I see why the old one lasted so long.

To fit the seal..hmmm that is not easy..I found circlip pliers good to expand it enough to get onto the piston, which did not damage the seal (soak in hot water first). I could not do it with my fingers.

At the mouth of the cylinder after the piston assembly had been inserted, I smeared a thin layer of red (brake fluid compatible) grease just to make sure that area does not corrode, but it does not come in contact with brake fluid when the seal is good.

Before fitting the cylinder, pop the bleed tube onto the nipple as it is difficult to gain access once the cylinder is in place. Make sure you don't over tighten the hydraulic line to the cylinder (there is a cone-shaped soft copper sealing washer in there) when its refitted and it's all good, then get somebody to help you bleed the clutch.

So I learned the hard way not to leave the fluid so long in the clutch next time and change it in two years when I do the fluid. I wonder if the seal was actually the factory fitted one..