Hi All

Looking for some help. My clutch stopped working so I ordered a new Borg and Beck kit with a diaphragm pressure plate. Decided to do it in-situ and removed the wok cover and the pressure plate and then found what I thought was my flywheel puller was in fact for another purpose. Put the new diaphragm on, aligned with 3 long bolts screwed into flywheel, fitted bolts through straps into pressure plate and adjusted bolts to correct torque. Replaced the the wok and as I replaced the pin for the lever arm, found the knob on the end of the lever arm was cracked and had changed shape. The knob broke off as I put pressure on it. So assumed this was the problem all along. Fitted a new one with new pin and replacement clutch slave cylinder. Set the lever arm gap and started the car to find the the clutch was not disengaging. Adjusted the lever arm adjuster, but this only changed the final stop point of the clutch pedal. The more I moved the adjustment out, the higher the stop point of the clutch pedal.

Got a new flywheel puller, replaced clutch plate. Set up diaphragm on flywheel external to vehicle, connected up to pressure plate put pressure on diaphragm and clutch disengaged. Fitted to motor with all the same precautions and same result. Clutch won't disengage

Any ideas?

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

Have you backed off the overthrow nuts on the clutch plunger ?
sounds a bit like the overthrow nut is touching the wok before disengaging the clutch , which also puts pressure on the clutch arm ball end causing it to crack or break off.
just my thoughts , I am no expert .

slacko

Thanks Slacko for the response and one that I thought of too, so yes have.

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

Sounds like your slave cylinder is reaching the end of its stroke.

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Cheers,
Rod.
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'63 Morris 850 (Old Secondhand CAR)

Another thought....
When you assembled the clutch off the car and in the engaged position, was the diaphragm spring flexed until almost parallel to flywheel? Then, when you put pressure on the diaphragm (disengaging the clutch), did the diaphragm spring flex overcentre?

There can be a mismatch when replacing parts of the clutch, for example where the 3 lugs of the pressure plate are not the correct length to clear a new and slightly thicker clutch plate. Replacement parts are not always to factory original dimensions - and it doesn't take much to upset a mini clutch.
This is explained by DrMini here, which is where I first heard about it.

viewtopic.php?f=25&t=100137

All good advice and have read the Dr Mini info before I posted. There was another step that I took that indicates that the new clutch parts are not the issue. In my first attempt when I changed the diaphragm and the clutch wouldn't disengage I thought the new diaphragm was faulty, so changed back to the original and put back together and this problem of not disengaging remained. So once I refitted the old diaphragm the only change in parts was a new lever and new slave cylinder. I checked the slave cylinder rod movement, and it is the same as our S. I believe there are only two types of clutch levers and the replacement i fitted looked identical to the original. I thought initially that I hadn't aligned the diaphragm so the clutch plate was not matching up with the pressure plate. I hadn't seen any advice about alignment of the pressure plate, but I couldn't think of any other reason for the problem, so I removed the wok again and aligned the diaphragm using the flywheel puller bolts and put it all back together and same result.

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

I'm 'clutching' at straws here....
1. The slave cylinder pushrod travel should be about 19mm to work correctly.
2. The diaphragm aligns into its groove on the flywheel and centres the pressure plate by the shouldered screws.
3. My only other suggestion is to check the clearance inside the flywheel centre hole. There is a machined shoulder that could bind onto the primary gear's retaining washers and nip the primary gear to the crank, preventing disengagement.
Check out Hickey Racing Engines on youtube:

https://www.youtube.com/watch?v=C3c5EcpYiP8 at about 4:00 mins.
https://www.youtube.com/watch?v=4lEbKGpZ4xw at around 7:00 to 11:00 mins

Of course the final answer will be something very simple.

Some of the wide flat faced release bearings can get hung up on the internals - doesn't fully seat - not sure what one is supplied in thekit so sorry if wrong suggestion

Thanks Bill B
Ah I hadn't thought about the flywheel shoulder binding onto the primary gear washers and it makes sense. When I removed the flywheel bolt I did notice that it was no where near the specified torque and so it could be that once I torqued it up to specs the flywheel has been pulled up the drive shaft a fraction more onto the retaining washers. I have no idea how I can check the clearance inside the flywheel centre hole in-situ so maybe I just get the shoulder machined out a little anyway.

FNQ, I thought about the release bearing not seating properly and it sounded like a possible problem to me too. However, because the motor had only done 3000m since its full rebuild, including new clutch kit, and the bearing fitted was still in very good condition, I did not change that over. Because the problem persisted once I put all the old parts back in, and the bearing is not the wider flat faced version I am guessing this is not getting caught up. Also, once I put the whole thing back together, in both circumstances with the old parts and the new parts fitted, I can see through the wok timing peep hole that the diaphragm is actually pressing in so it appears that the clutch bearing is doing its job.

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

It was all working before it stopped, so the flywheel to primary gear clearance etc. should be fine

It sounds like the only thing you haven't tried is to adjust the throwout stop bolt incorrectly - screw the bolt out a decent amount so it's permanently pushing the arm. Pump the pedal a few times and then see if the clutch is disengaging. Basically you want to figure out if the clutch can actually disengage.. if it does then I'd be looking at the throwout plunger and release bearing

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did I tell you that I won a trophy?

As you perform this adjustment the slave piston retracts less. If the piston is reaching the end of it's stroke each time you press the pedal you will see the less downward movement you speak of. (Yes I have experienced this myself in years gone by... )

Remove the pushrod pin, pump the slave to its end of stroke and measure from the pushrod pin hole back to a fixed point on the cylinder itself. This will give you the maximum extension measurement of the slave cylinder.

Reassemble and operate the clutch. If you reach this pushrod measurement then you have your answer!

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Cheers,
Rod.
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'63 Morris 850 (Old Secondhand CAR)

Hi Rod and Simon

Away for a couple of days, so will try both ideas as soon as I get home. Have adjusted the throwout stop bolt and the further out I adjust it the smaller the range of the clutch pedal and still no clutch release. However, will try again after pumping and will bleed again and then also check Rod's idea about the slave cylinder rod movement.

Thanks again

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

Hi Alll.

Found the problem. The pin in the new slave cylinder is slightly smaller than the original and with the replacement lever, the geometry of the system didn't work. Lengthened the slave cylinder pin with a work-around and adjusted the lever stop bolt and works perfectly. Will put an order in now for an adjustable slave cylinder pin so I can get enough movement in the lever arm.

Thanks everyone for your great advice in helping me track down the problem.

Bazzz

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Mini Cooper S Mk 2, 1970,
Mini van 1970 with side windows now converted to 4 seater traveller

I had a similar problem, eventually found this out too, i have extended the pushrod and now it all works well. Theres not enough wiggle room in the mini clutch for everything to not be spot on even with new parts.

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1972 Mk3 Mini 1000, 1150cc supercharged.
https://www.ausmini.com/forums/viewtopic.php?f=3&t=95872

The other option is putting a washer underneath the thrust bearing. I did that to mine and it resulted in no more crunching when going into any of the gears and brought the clutch grab point up to the middle of the pedal where it was previously right at the floor! Cost less than 50c to fix.

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-----Better is the enemy of good-----
-1976 Yellow Devil Leyland Clubman-
-1970 Morris Mini Van - Work in progress-