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MG MGB Technical - Dude, where's my clutch?

Help please, my 73 B won't go into gear. I needed to move it and the clutch does absolutely nothing. It worked fine when last driven in October. No resistance when pushed in, but the return spring does bring it back. It does have fluid in the cylinder. This past summer I needed to add some fluid and used just regular brake fluid, not Lockheed. After doing this a co-worker informed me that she had done the same thing many years ago in a midget and ruined all of the seals. I figured if I'd ruined the seals I wouldn't have fluid left so I kind of ruled that out. Plus I don't have puddles of brake fluid on the garage floor. So I guess my next place would be bleeding the system? If so, should I switch to Lockheed or should I stick with whats already in the system? Am I on the right track or do I need to dig in really deep?
S J Kelly

When you say you used regular brake fluid I assume you mean a name brand DOT 3 fluid. Most people use Castrol DOT 4 but I have used Motorcraft DOT 3 in MGB brakes with no problems. I would start by bleeding the system and use Valvoline or Castrol DOT 4 to top the cylinder off. I suspect you have a leak because it had to be topped up several months ago. Pull the boot back on the slave cylinder and look for fluid, it should be dry. If the slave is ok check for fluid above the pedal around the master cylinder push rod. I doubt that the DOT 3 fluid caused the problem, someone will duspute that statement, but I stand by it based on my personal experience. Clifton
Clifton Gordon

I had the same thing happen to a 68 Migii, but by 73, I thought the rubber was compatable with the DOT 3. I would have someone crawl under while another operated the clutch to see if there is any travel in the slave cylinder. Probably in the hydraulics. opefully it is in the hydraulics).
Bruce Cunha

must be a leak. DOT 3 is OK on the MGB. DOT 4 has higher BP but is otherwise the same as DOT 3.

You may have a clutch disk rusted to the flywheel. Very common in humid areas. Try putting it in gear (e-brake on) and depress the clutch. Now, put right foot firmly on brakes and attempt to start. No spinning of engine confirms diagnosis.

Elsewhere in archives are various suggestions for freeing it.


Thanks guys. I'm pretty sure I don't have a leak. It was topped off with at most two ounces in August. I drove the car alot during the summer and it seemed to work fine. I will get the bugger up in the air this week and start double checking though. I guess while it's there I may just bleed it to make sure. Boy I really hope it's the hydraulics too. Mike, it does start fine. I've been running it for a while every couple weeks to keep fluids circulating while I'm waiting for the snow to melt. Again thank's everybody for the help.

S J Kelly

Sounds like the clutch disc is stuck to the flywheel. Not an uncommon problem as Mike said. One way of freeing it is to try and start the car in gear. Remove the plug wires so that the car cannot start. The jolting sometimes breaks the clutch disc free. Try reverse as well as forwards. Remember the car will move forwrds or backwards when you try this so make certain you won't hit anything.

Good Luck Andy
Andy Preston

I'm with the stuck-clutch-disk-group, had it twice after long storage.
Willem van der Veer

SJK - Your symptoms are the same as I had on a 77 GT. Turned out to be the master cylinder. New seals didn't cure the problem, I had to replace the whole unit as the bore was scratched. There seems to be a very fine line between working or not working! The MC went very suddenly with only a day or so of slight difficulty engaging reverse. My GT had been standing outside a local mg specialist garage for a month or so, but drove fine on test. One week later - no clutch! As Bruce says first thing to check is for movement at the slave cylinder operating rod.

Laurie Webb
L Webb

You've hit the nail on the head when you say "no resistance when the pedal is pushed down" It's definitely a hydraulic problem so sort that out and the problem will be solved.
Iain MacKintosh

I had a similar problem with my 75 B, replaced all hydraulics with new, tried all of the suggested methods of freeing up rusted clutch assembly, none of which worked. On a whim I dislodged the rubber boot at
the slave cylinder to trans area and found chunks of metal falling out. Turns out my pilot bearing dissinigrated. Don't really know if this is common or not.
C.A.H Chuck

Before diving in check whether it *is* the hydraulics or not but looking at the slave piston while someone else (I presume) operates the pedal. You should have 1/2" to 5/8" of travel of the slave piston. If so then the implication is that the clutch is stuck, which can be freed by towing it round in 1st pumping the pedal, jacking up the rear running the engine putting it into 1st with the pedal down and dropping it off the jack, etc.

If you have some movement but less than this it probably needs bleeding.

If you have no movement it may have a lot of air, or the master seals may be buggered.

Bleeding is easiest done in reverse, but to avoid pumping dirty fluid into a good master open the bleed nipple and pump the pedal until the fluid runs clear, then use an EeziBleed on very low pressure conencted to the slave nipple to refill the system. You only need to fuill it half-way or so like this, then top-off as normal.
Paul Hunt

Again, a very big thank you to every one. Guess I'll be under the B feeding it Valvoline instead of diving. Oh well, it's cold any way. Again, Thank you.
S J Kelly

This thread was discussed between 10/01/2005 and 12/01/2005

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