Question on Release Bearing

[david.g.chapman]

I Just want to confirm something.

When the clutch is fully disengaged with the 2.03mm gap on the release arm, does the release bearing thrust face still touch the clutch diaphragm assembly (with no load on the bearing), or should there be a gap?

Dave Chapman

[Sea Ranch]

Sorry . . . do you mean when the clutch is fully ENGAGED? As in when your foot is off the pedal?

[J.E.S]

Assuming you do mean when your foot is off the peddle (the clutch plate being clamped between the fly wheel and clutch cover) - yes its my understanding that the 2mm clearance between slave cylinder push rod and release arm and will mean that the release bearing is held back from the clutch.

John.

[AussieJohn]

If you have clearance then the spring on the slave cylinder keeps the bearing off the pressure plate.

[david.g.chapman]

Yes, foot off the pedal.

I find that I have to give about 4mm of play before the bearing comes away from the clutch (peering into the bell housing) - there seems to be quite a lot of slack to take up in the single turn springs and bearing carrier before this happens. I have run the clutch for some years and 20000 miles with the bearing sort of resting on the clutch, but probably with the slack the bearing floats about and comes away part of the time.

The clutch feels normal under these conditions and the bearing is quiet.

I can use the clutch with 4mm of play but the bite point is low.

I suppose I could carry on with 2-3mm of play and keep lubing around the bearing with spray grease until there is a more pressing reason to pull the engine out.

Dave Chapman.

[david.g.chapman]

After more keyhole investigations I know what is going on.

When the engine is stopped the release bearing thrust face tends to stick on the clutch. Backing off the pushrod adjustment to give more play and operating the release arm led to a 5-6mm arm movement before the bearing came unstuck. It then sprung back under the action of the two single turn springs to give a 2mm gap between the thrust face and the clutch.

This would correspond to a small thrust face gap under normal adjustment conditions (2.03mm). I tried with the engine idling and the stickyness improved. (i.e less sticking)!

After a squirt of PTFE spray lube in the thrust face I set the adjustment back to normal. The bearing still sticks a bit but comes away after a second or two - good enough, as things would be much better under driving conditions.

Something to check for when I adjust the clutch in future - and thanks to your replies I know what to aim for

Dave Chapman.

[oldelanman]

After a squirt of PTFE spray lube in the thrust face I set the adjustment back to normal. The bearing still sticks a bit but comes away after a second or two - good enough, as things would be much better under driving conditions.

Dave,
I could be wrong here but I think lubricating the thrust face may be the cause of the sticking and not the cure. It's like a tappet shims in the cam bucket or a bearing shell on the crankshaft journal - they tend to stick when oiled but not so much when dry. I also recall from my apprentice days having to lightly oil gauge blocks (Jo blocks) to aid sticking when wringing them together.
I wouldn't worry too much about the bearing sticking a bit when the car is stationary, so long as you have the clearance set correctly the bearing will not be loaded and the clutch will be fully engaged.

Regards,