I'm a new member hoping to find some expert advice on a mini pre-verto clutch. Mk 3, 998 mini, 1974 vintage.
The car is coming to the end of a 4 year rebuild and looking good - but the clutch don't work! Very frustrating.
Basically, the clutch disengages but only when you get to the last 1/2" of travel of the pedal. I've tried every which way of adjusting the stop bolt and the throw out stop nuts (nearly typed 'Back Stop' nuts then!). The system is bled with a Eezibleed pressure bleeder and I'm confident there is no air in the system. There are new clevis pins everywhere - the operating arm is new - new master and slave cylinders - new throw out stop plunger - new braided flexihose - new clutch plate, diaphragm and release bearing. The flywheel and pressure plate have been skimmed and (not trusting my own judgement) I asked the chap at Guessworks to look at the height and set up of the drive straps and he agreed they were fine. I opted for DOT 5.0 (Silicone) hydraulic fluid which, I don't think should be a problem - it's working fine in the brake system. The pedal and pedal box and the clevis pin are all in good condition - no oval holes - and there is nothing restricting the movement of the pedal down to the floor.
Someone suggested bending the operating lever towards the slave, which I know I shouldn't need to do given that the linkages are all fine and mostly new, but I tried it - no difference.
So - I started checking things again and noted that, even with the throw out stop nuts backed right off, the slave cylinder push rod was only moving about 3/8". This level of movement did not change with the clutch return spring disconnected or with the clutch operating arm completely disconnected either. The suggestions on the interweb say it should normally be 1/2" to 5/8". So I took the (new) slave and master cylinders apart and found a big chunk missing from the lower seal on the master cylinder, Ah ha! I thought - here is the problem. The bore looked fine so a new seal kit was fitted with high expectations that it would solve everything but no - it's still only moving 3/8". The slave cylinder looked fine. The bore of the slave is 7/8" and the master is 3/4".
I can't see any leaks in the system anywhere. In the (very) short distances I have been able to drive it there is no evident slip but there is drag sometimes depending on how I set the stop bolt etc but given that the clutch is only disengaging when the pedal is just a few millimetres from the floor I suppose this isn't surprising. I can't drive it far, partly due to the clutch and fear that I will not be able to get into gear when at a junction, but also because the engine is running rough due to a stage one kit being fitted and (I suspect) a need for a different needle in the carb. I'll get this sorted on a rolling road, but, I cant do that till the clutch is sorted!
I've spent about 6 weeks on this so far. Am I missing something obvious? I don't really understand hydraulics but is it possible, given the lack of travel in the slave pushrod, that it's still a hydraulic problem and should I try a replacement slave or master cylinder (or both)? Any ideas much appreciated as I've run out of them.