Clutch not clearing.

[Broadspeed]

Hi, we are building from a new shell and write off a MK111 Cooper "S".
We are having problems getting the clutch to clear and was wondering if we were getting the right amount of hydraulic operation
A couple of questions please.
Is the clutch pedal always lower than the brake pedal and by how much ?
Are the clutch and brake master cylinder push rods the same lengths ?
Thanks
Mike

[Spider]

Hi, we are building from a new shell and write off a MK111 Cooper "S".
We are having problems getting the clutch to clear and was wondering if we were getting the right amount of hydraulic operation
A couple of questions please.
Is the clutch pedal always lower than the brake pedal and by how much ?
Are the clutch and brake master cylinder push rods the same lengths ?
Thanks
Mike

The Clutch pedal is either the same height or a little lower than the Brake Pedal

Unsure on the pushrod lengths, I've never compared them, could also depend on which Brake MC you have.

Sometimes there is a shim and even a thick gasket under the clutch MC, I never fit them.

Just to be sure nothing's overlooked, the over-throw nuts on the clutch cover, you have plenty of clearance between them and the clutch cover?

The Arm and pins are all in very good condition?

The clevis pins and holes in the MCs and pedals also wear, so check these too.

If you open the little timing cover on the clutch cover, and then turn the engine over by hand until you can see the bolt heads that hold the clutch diaphragm on, and make a measurement on the bolt head height to a reference point. Then have an assistant press the clutch pedal down and make another measurement. There should be around 0.050" Anything less than about 0.040" and you'll likely have problems and it is (as you are suspecting here) the hydraulics and / or linkages.

[814CWE]

also check crank end float,,excessive float causes non operative clutch

[Broadspeed]

Thanks for your replies and info.
Mike

[nick@dunsdale]

Just to be sure nothing's overlooked, the over-throw nuts on the clutch cover, you have plenty of clearance between them and the clutch cover?

That's the usual culprit.

The rough chaps used to bend the clutch arm, ancient bodge from back in day lol

[LDR209H]

Is the pedal heavy as well ? Could be the flexible hose 'ballooning' out.

[guru_1071]

this is a set of instructions i sent someone who was having problems with clutch clearence. it fixed his problem.

anyone who has to bend the arm or increase the length of the operating rod is simply masking an underlying problem in my opinion.



its an annoying problem! its caused by tolerances moving around i think.

this is what i do when i have built a new engine/box.

jack car up so wheels are not on the ground (so nothing can snatch or run you over)

remove the clutch return spring

let engine warm up

you then need a girlfriend / helper who you can trust....

undo the big nuts so they dont get in the way - all they do is stop the clutch going over centre, so they dont matter at this stage

wind the little adjust bolt out as far as it will go, so the clutch arm is as far out as it can be

pump the clutch a couple of times, this will make sure that the piston is as far out as it needs to be.

start the engine

get your helper to try and put the car in first gear, if it baulks put it back into neutral and wind the small bolt back in a couple of turns. get them to try putting it into gear.

repeat and repeat until it goes into gear with no cruch.

once its goes in, keep going with the bolt (but make a note of how many flats you turn it) until it starts to baulk again.

you will then have the sweet spot between the upper and lower range of the clutch adjustment - then set it in the middle (normally 3-4 full turns of the bolt)

let the car down onto its wheels and try again into first and reverse - it should go in fine and not slip. if it does slip wind the bolt in until it stops plus a flat or two more more (you should still be in the 'sweet spot')

once your happy with the position of the adjust bolt turn the engine off

press the clutch down and wind the big bolt up against the alloy housing, then let the clutch off and wind the nut one more flat and nip the lock nut up.

it should now be fine!

you will probably find that you will never get the ten thou clearance betwen the clutch arm and the little bolt as it would have been from new

[Red1967]

I had the same issue. No matter what adjustments I made nothing would resolve the issue. Every parts was brand new. Then I modified my clutch push rod by cutting it. tapping both ends. Insert a set screw and two nut to allow you to adjust the push rod's length. Worked like a charm.

Like this one from Mini Mania

http://www.minimania.com/part/C-13H396/ ... ve-Pushrod

[Red1967]

No car out there has ever needed any type of modification other than what is stated in a manual. Obviously I am not the only one that has ran into this issue or this part would not have been made and sold. Is it possible that maybe the push rod I purchased was not made to the correct length? I guess I will switch back to a solid push rod and spend hours again trying to get my clutch to work.

[Spider]

I had the same issue. No matter what adjustments I made nothing would resolve the issue. Every parts was brand new. Then I modified my clutch push rod by cutting it. tapping both ends. Insert a set screw and two nut to allow you to adjust the push rod's length. Worked like a charm.

Like this one from Mini Mania

http://www.minimania.com/part/C-13H396/ ... ve-Pushrod

I did that once, only to discover the next day that there were 2 different length pushrods! I didn't look too far in to it, but I think one's early, the other late. I suspect it may have been changed / up-dated along with the arm at some point.

[1071 S]

Really looking to be educated here.... are we discussing verto/pre-verto/does it matter????

I just don't understand guru's logic??

(all comments apply to a non-verto clutch - 'cos I've never (sic) seen the other kind)

Once the flywheel/clutch/diaphragm etc are bolted up, the "engaged" location of the release bearing shuttle is fixed. Once the wok is bolted up the location of the bottom of the clutch arm is fixed. Assuming a standard (geometry) arm and in-tolerance pins and holes, so is the top. By engaged I mean the diaphragm is locking the clutch plate (and gearbox input gears) and flywheel/crank together to provide drive.

The stuff (master cyl/slave/clutch arm etc) outside the "wok" only exist to compress the diaphragm and release the lock between the crank and input gears.

The only thing the length of the slave push rod determines is the location of the slave piston within the cylinder. If the rod is too long it won't fit - the piston will be pushed to the back of the cylinder and the other end of the rod will extend past its locating point at the top of the clutch arm. You won't know its too short until you push on the clutch pedal and find that the piston runs into the outer retaining circlip before enough travel has been achieved to release the clutch.

NOTHING you can do to the pushrod/clutch arm will increase the piston travel. (well, nothing easy - the ratio of top of arm to bottom of arm movement is the same as the ratio of teh distance from each end to the pivot) Normal wear (clevis pins/holes/lower clutch arm ball/release bearing socket) will see the engaged location of the top of the clutch arm move outwards until the normal travel of the piston is interrupted by the retaining circlip. If you're really unlucky, a PO will have found that they can get a bit more travel by removing the circlip - this works fine until sufficient wears occurs to allow the piston to fall out of the slave cylinder. This is why people bend clutch arms/ lengthen push rods...

There are only two "adjustments" (as opposed to fitting replacement bits) that you can make with a Mini clutch. The small nut on the wok is to reduce hydraulic float in the slave (its stops the piston being pushed back beyond the point where the clutch is fully engaged). The big nuts on the release bearing shuttle stop the clutch over throwing - which I have never seen - nor do I know anyone who has... I have seen web accounts of it occurring - but I don't bother...

Once you have the slave shuttle operating in the middle (more or less - its only critical if its too far out) of its travel (by adjusting the push rod length) there are two things you can do to increase the range of travel if necessary. You either increase the bore of the master cyl - or reduce the bore of the slave (BTDT)... (When i fitted my Manx Racing flywheel I found the distance between the clutch face and the spring locating face was different from that of standard flywheel. The differnce was accomodated by changing the push rod length),

Oh dear - did I type THAT much...

Cheers, Ian

[Spider]

Hey there 1071 S,

Pre-verto all the way here

The pushrod length can have a bearing on clutch operation as what happened in my case was that the pushrod was too short and so the piston in the slave cylinder was hitting the circlip before getting enough movement. Now, keep in mind the intial starting point for the pushrod is set by the adjustment bolt. I possible could have gotten enough travel by removing the circlip, however I do like to have them in there.

Now, the arm. Keep in mind these have very high leverage ratio, so if they start off at the wrong angle, then the over all movement on the plunger is going to be reduced. This is why the arm and the plunger have to be replaced when they wear.

As for Verto stuff, the only experience I have with it was the first time I drove a Mini with this set up, I thought I had broken something as the pedal was so light

[1071 S]

"Pre-verto all the way here "

Great.... comments relevant

"The pushrod length can have a bearing on clutch operation as what happened in my case was that the pushrod was too short and so the piston in the slave cylinder was hitting the circlip before getting enough movement. Now, keep in mind the intial starting point for the pushrod is set by the adjustment bolt. I possible could have gotten enough travel by removing the circlip, however I do like to have them in there."

Uuumm yes?? I could repeat myself but see above for full comment "(Normal wear (clevis pins.........................If you're really unlucky, a PO will have found that they can get a bit more travel by removing the circlip - this works fine until sufficient wears occurs to allow the piston to fall out of the slave cylinder.) "

"Now, the arm. Keep in mind these have very high leverage ratio, so if they start off at the wrong angle, ..."

I would suggest (well, actually I already have..) that there is no "wrong angle" - they are where they are. Wear just increases slop ..see Comment 1.

Cheers, Ian

[guru_1071]

my logic is fine

one of the problems people have is that they are using steel flywheels etc, or cranks that have had the tapers cleaned up, things like this move the assembly nearer the engine, which means the clutch mech is doing more work, in a different place.

one problem i have seen so many times (hence my instructions ) is that people fit a new slave cylinder to a dry system, bleed it them start pressing the pedal with the piston right up near the bleed nipple, in this situation, the piston is only operating at the very inner end of the cylinder, so the arm isnt getting the 'full leverage' it needs, by 'walking' the piston to operate at the mid point it helps greatly.

clutch adjustment is one of those things that every one has their own ideas of what works / what doesnt - i know my system works!


as for vertos, they are a great clutch, self adjusting, feather light etc etc - the biggest issue with these is animals thumping the flywheel through the starter hole trying to get them off and bending the clutch spring!

[Spider]

1071 S, I have a drawing / pic somewhere that shows the problem when the ball on the arm and / or the plunger wears, it does cause a loss of total travel. When I find it, I'll post it up.

my logic is fine

one of the problems people have is that they are using steel flywheels etc, or cranks that have had the tapers cleaned up, things like this move the assembly nearer the engine, which means the clutch mech is doing more work, in a different place.

Usually a washer or shim between the bearing and the plunger helps

[guru_1071]

Usually a washer or shim between the bearing and the plunger helps

that would work, but you would need to dry build it all first, it would only work with the fixed bearings, not the floating ones