Lesson learned [I think] on slave cylinder.

[TR4nut]

After 6 months of putting off replacing a tired clutch in my TR4, I did manage to complete the task on New Years day. Unfortunately I found that the finger-style pressure plate was badly worn also due to the use of a wrong throw out bearing, so I replaced everything.

Buttoned it all up, and it worked great.. for about a week. Although I was very careful with the slave cylinder and moved it out of the way when I pulled the transmission, after I reinstalled everything it wound up leaking which I finally figured out last weekend when it failed on me.

It's fixed again as I had a spare slave ready to go, but I think its taught me a valuable lesson - with the new clutch in place, the piston was running in a different area of the slave cylinder. I suspect that although the cylinder was in decent shape, the piston seal had developed a 'set' to it which caused the leak. That's my theory anyway, I'd be interested in hearing if others have seen that or have a different thought.

What that tells me that in the future (very distant future hopefully), if I do a clutch job I'll be thinking of changing seals in the cylinder at the same time.

Randy

 

[tdskip]

Thanks for the heads-up Randy.

 

[TR3driver]

That shouldn't be the case on a TR4. Unlike the later TRs, you should have a return spring on the slave cylinder, that always fully retracts the piston. The adjustment at the clevis (which needs to be updated from time to time) is what compensates for changes in friction plate thickness.

The return spring should also lift the TOB away from the pressure plate slightly. So the wear you mention makes me suspect that your spring is either missing, or too weak. The correct spring is very strong so that it always overcomes the friction of the piston & seal immediately, a cut-down screen door spring isn't going to work properly.

Improper adjustment can also lead to rapid clutch wear. Kept properly adjusted, the stock TR2-4 clutch seems to last almost forever; mine had over 100,000 miles on it before I installed the alloy flywheel (which took a different clutch).

 

[NickMorgan]

It is interesting how often when one part is replaced the next link in the chain breaks. I suspect that your slave cylinder was close to the end of its days and the extra pressure required to depress your new clutch was the final straw. You had better watch your master cylinder now!!!!

 

[TR4nut]

Randall-

You bring up a good point - I replaced the hydraulics about 3 years ago, and adjusted to proper clearances at that time. There was no return spring when I bought the car, I added it during that changeout. I suspect the damage to the pressure plate was already done at that point. Need to load a picture to show it, but the fingers were nearly worn off, so the clutch lever position was significantly rearward relative to where it is now with the new pressure plat. Bearing looked like it may have been a later TR6 style ie it wasn't flat, and it cut concave depressions in the fingers. Never squealed though during operation.

When I installed the slave again, I reset clearance on the clutch (0.1" if I recall correctly) which moved the clevis quite a bit relative to where it was - but you are right, the piston should be bottomed the same way as before. Perhaps the leak was just nothing more than the piston moving during the operation a little more than normal clutch operation. I was careful not to touch the clutch pedal during the operation though so it still leads me to think that seal leaks can happen pretty easily.

Randy

p.s. Nick- just saw your post, unfortunately relatively new slave and clutch master so it looks like I was the cause.

 

[prb51]

Randy,
I recently put a new clutch plate in when changing the tranny (toyota plate) on my TR3 and used the original pressure plate (looked pretty old but works just fine) and had no issues with the slave.
A friend told me as we changed it out that he rarely changes the pressure plates out on TR3's as they last a long long time if everything is right.
Since the slave wasn't touched (adjusted) and the pressure plate remained it felt exactly the same....I did the double whammy by changing to dot5 by just bleeding out the old dot4 (overbleeding) and still no issues.