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MG MGB Technical - Clutch help!!

hoping someone can help with a clutch problem. 1979MGB just imported from UK (my own car owned for 23yrs. With the clutch pedal all the way to the floor it is difficult to engage gears and when on the move its difficult to change, gears seem to be holding on. clutch has 4000mls on it after i replaced the overdrive in '01. Its been stored for the last 22months but run regularly. I'm guessing its hydraulic and need to refurbish master and slave but wanted to ask a second opinion. Got it on the road and only done 140mls since getting it over here, fluid level is down a bit so hoping its passing a seal somewhere. Any thoughts guys? (or gells !!)
jon whitehead

With the car safely supported and someone pushing and releasing the clutch pedal its full travel, measure the travel of the slave piston, you should see 1/2" to 5/8". Unless fluid is pissing out and the level is well down it won't affect travel, unless it has *been* well down and you refilled it, in which case you may have air in the system and it needs bleeding, which will be evident from short slave piston travel. If it hasn't been used for a long time it may just be sclerosis of the clutch plate or pilot bearing, give it plenty of use including a few seconds of slipping the clutch at a couple of thousand revs in 4th with the brakes on to burn it off. My V8 gets that if it isn't used regularly.
Paul Hunt

Looks like it is hydraulics. Get someone to depress the pedal and see how much the fork moves. It should be at least 1/2". I'll guess that the movement is someway short of this and there is a possibility that you will find fliud leaking where the pushrod enters the boot and that there will be a lot of fluid behind the boot. If not you will find the fluid leaking from the master cylinder pushrod in which case you will have to rebuild the master. That is a bit of a pig of a job which you will find on another current thread. As a last ditch it could be that the flex hose is balooning under pressure but that's doubtful. It could also be that there is so much wear on the pedal/pushrod holes and clevis that much of the movement is being lost taking up the play but you will be able to feel this by depressing the pedal lightly by hand

If its none of the above then it's clutch out again I'm afraid.
Iain MacKintosh

I went through much frustration and expense trying to get my clutch pedal off the floor.

New everything. No fooling, new press plate, master & slave I even re-routed the piping to get it less likely to trap any bubbles. The grand result? NO IMPROVEMENT!!

My solution? Fit a 'midget' slave cylinder. The holes match up, althought you'll need to space it out with a distance peice,,,,you'll have a solution.

The midget slave has a smaller bore and will push further
when the master sends the fluid.

Works very well for me.

stewart caskie

First step, check that it isn't just disuse (as above) - The way to KNOW it's not hydraulic: if the release point is right on the floor, you've probably got a hydraulic issue. If the release point is in the middle of the pedal travel, the hydraulics are likely OK and you've got a dragging friction disc. If it's not hydraulic, it may well be rust from sitting about - slip the clutch gently, and for a number of seconds, and see if the surfaces clean each other off.

If you determine that the issue is hydraulic:

Definitely check the flex hose before worrying about anything more difficult or expensive. Just swap it out, it's ten bucks well spent and no, it's not unlikely to fail on a car that's been stored. Hoses that appear OK are often not. **DO NOT assume your flex hose is good!!**

On replacing the hose, bleed the system thoroughly! and test.

Checking the slave cyl is easy - look under the rubber boot. If it's bad it leaks, and if it leaks it's bad.

Assuming you've eliminated all those as possibilities, look at the master. The master is a bit of a pain, so do it last, after testing the easier parts in the system!

If your engagement near the floor there is something wrong that can be fixed properly. Using a Midget slave is a frig and poor practice. Unless the hydraulics need bleeding the usual cause of low engagement is worn pedal and master push-rod holes and clevis pin. On my roadster I reckon the combined wear on these items added up to an inch of pedal movement. I replaced the clevis pin, had un unworn push-rod from a previous master change, and welded-up and redrilled the pedal hole.
Paul Hunt

In answer to Paul.

Hi Paul, when I listed the cures I tried, I didn't mention the full inventory. I did as you suggested, first. New master cyl. new slave, new pin & clevis, I checked the pedal pivot (re-bushed it) ...I even got a whole new body from Doug Jackson (another story).

I was pretty meticulous in re-assembly of the car, I've owned and driven it daily for 16 years amassing an impressive mileage including a coast to coast trip in 2002.

I never solved the pedal to the floor issue...period.

What's left but invention? At least using parts from the same maker avoids the bodger label.

I don't think if something is mechanically sound and performs well that it's bad practise.

I stand behind this mod as it was the only cure I ever found and it has worked flawlessly for 6 years.

Re: the distance piece, Doug Jackson makes and sells a kit to keep the clutch release off the bearing. It mounts under the slave cyl and provides enough stand off to solve clearance issues on my car.

In the UK your cylinders are both on the same side with short piping, over here, the piping has a fair way to go... and holds more than the amount of fluid moved by cylinder activity. Bleeding can take ages.

I stand by my suggestion.
stewart caskie

Weld the clutch up.
Makes traffic a bit awkward, but it can cope with mucho horsepower
Mr Noble


I had exactly the same problem for months after replacing the clutch and put it down to an enthusiastically surfaced flywheel combined to a dying slace cylinder.

Eventually, the slave cylinder developed a leak so I replaced it. My problem was not solved.

Ever since I had had my MGB, the clutch pedal was very noisy, producing an unpleasnt grinding sound. One day I could not take it any more and investigated: the Ushape-ended pushrod linked to the clutch pedal via a thick pin was showing a lot of play. The pin was severely worn, making the cluctch pedal almost inoperant on the MC. I replaced the pin with a simple bolt and... miracle, no more noise and a perfectly functioning clutch!!

I have now bough a new Ushape-end rod and pin to fit all back to original.

Good luck

This thread was discussed between 23/11/2004 and 30/11/2004

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