21 replies to this topic

[tjllanrug]

My clutch pedal went hard few weeks ago and i found out the bolt was lose , i got a new washer key way one
and put it back on, had a guy up the road who deals with minis to come and close it, put it all back together, same thing happend again come lose clutch pedal hard then flywheel getting lose , waht causes this why ? thanks

[tjllanrug]

The locking tap is there aswell ** and still opens

[ANON]

what's the crank tail like?

[tjllanrug]

what's the crank tail like?

All look good

[tiger99]

You need to lap the flywheel to the crank with grinding paste to get a good fit, and then (after cleaning all traces of grinding paste!) torque it up correctly. You may even want to leave it a few minutes, loosen slightly, and torque it again, in case it creeps.

The key can not transmit dynamic load, which is all done by the tight fit of the taper, so it really must be tight.

[bmcecosse]

If the flywheel has come loose - the crank tail CANNOT be good....both crank and flywheel hub will now be scrap......

[tiger99]

It depends on how long it was loose for. I knew one which lasted at least 50k miles after being found to be loose, and re-torquing without even lapping. There is very little to lose in trying to fix it.

[bmcecosse]

It's already been tried again........but do have another go, although I fear the worst.

[samsfern]

Loctite on the bolt?

[tiger99]

No! The bolt loosening is NOT the problem if it has been properly torqued and the locktab done up. The problem is entirely due to the fit of the taper, or lack of proper torque, every single time, unless there is a crack in the flywheel. Use the wrong grade of Loctite, and the bolt may never come out again, which will mean major problems if the flywheel comes loose again.

The taper MUST be a good lapped fit, and the bolt MUST be torqued up correctly, or failure is inevitable. All the Loctite in the world will not help. And please, no Loctite on the taper.

There are far too many instances of this problem on the forum, and this one seems to have been attended to by a supposed expert, who isn't. That makes me very sad.

[tiger99]

And one more thing, which will prevent the correct torquing procedure from working. There needs to be clearance between the key and the end of the crankshaft, if it bottoms the bolt is not clamping the taper. But I have never heard of that problem at the clutch end, although a dimensionsl problem at the other end of the crankshaft leading to a loose pulley is quite common.

[tiger99]

Oh, and why are we seeing so many loose flywheels nowadays? That used to be quite uncommon. I am guessing that maybe almost all Minis on the road today have had a clutch change at some time, often by a garage who don't know much about Minis (Mr. Clutch or worse...), leaving problems behind which only surface a long time later, when the cars are in the hands of new owners.

It is all very sad and unnecessary, and a very good reason for advocating the need to do things correctly, to avoid trouble in the future.

Hopefully this particular car will respond to a lap and retorque, and not need a crankshaft and flywheel.

[Sprocket]

'Lapping in' a taper joint? Consider this. You are introducing small radial ridges (peaks and troughs) on the two mating parts, which 'grab' each other when the joint is tightened. The torque used on th bolt to pull the joint together will be reached while not stretch the taper on the flywheeel as much and the interference fit of the parts will not be as high as it could be. the slightest Imbalance in the flywheel with the flex of the crank will then allow minute movements in the joint weakening the interference even further as the 'peaks' wear, resulting in localised micro welding (fretting).

I heat the flywheel and fit it hot, tightening the bolt straight away, thus shrinking the taper onto the tail of the crank. It's a right ball ache to get the thing back off though. There are all sorts of weird and wonderfull ways of tightening the flywheel joint, but I don't think the factory would have had the time do do these.

[tiger99]

They are often lapped nowadays, and I think the reason is because they have mostly been off a few times at least now. There is a tendency for localised welding to occur between the surfaces, and when you pull them apart you get some roughness which prevents them fitting so tightly again. The lapping removes most of that, but because the pits and bumps which you are removing are distributed at random you should not get significant radial ridges. Ideally you would grind the two parts seperately to a very good standard of finish, but that is not feasible for most people.

My reservations about fitting them hot are based on another recent thread, where the flywheel could not be removed. It may be necessary here as a last resort, as there may be so much wear that it needs to be both lapped and fitted hot.

If fitting hot, it may be advisable to drill and tap the holes for the flywheel puller to the next size up and modify your puller accordingly, in the expectation that getting it off again will be difficult. Easily done with the flywheel on the bench, not much fun in the car.

I like to aim to anticipate and avoid creating problems for the future. Sometimes you can, sometimes you can only do the best with what you have. In this case it may be that the flywheel can be fitted tightly, but will never come off again. If it is not a rare and expensive version of the A series, that risk may be acceptable.

[Sprocket]

Another option that reduces fretting and saves expensive modified crankshaft from frett damage