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MG MGB Technical - clutch pedal travel

Driving today, I suddenly found the clutch pedal had all but become useless. Before, there was a slight amount of free play in the pedal, but now I experience free travel for approximately 80% of travel. The archives mentioned a 3/8" travel in the slave cylinder plunger, but I only measured 1/4". Also, bleeding didn't seem to have much effect. Last thing I noticed was that whenletting off the pedal, the slave cylinder did not return fully in its bore and could be manually depressed quite some distance before reaching the bottom of the bore. I've had a rash of clutch replacements in the last 12 months, 3 of them in particular. I feel pretty fed up at this point, and really don't want to have to do it again...a couple more jobs and I might as well have bought the hoist...maybe I should look for a rent-to-own one out there. Anyway, I was thinking pressure plate spring, but could it be anything else? I have a relatively new (2 years) slave cylinder, braided steel hose, original piping and master cylinder. The car is still driveable at this point. How long might I expect tit to be so before becoming completely undriveable. Unfortunately, the B is my only form of transport from home to the University and to work, so I can't afford it to be down long. Any suggestions on what to check first before I devote the weekend to doing the engine pull thing? It's a 69, by the way. Oh, and while I'm here, under braking with warmed up brakes, I get a severe left-hand pull -- only when brakes are warm though. Passenger side caliper piston expanding in the bore and freezing? Thanks. I appreciate the help.

Mike
Mike Lord

Mike. It sounds like the master cylinder is in need of rebuild. No need to pull the engine and tranny to do this. The slave cylinder does not "return fully to its bore". The force of the clutch pressure plate pushes the throw out bearing backwards, which forces the pushrod backwards, which forces the slave cylinder piston backwards. Thus, the mechanism is self adjusting. The master cylinder is the most probable culprit, especially if it has not been rebuilt. Seals on the slave cylinder will also cause this problem, but, I would assume that it has been rebuilt if you have replaced the clutch three times. It sounds like a hydraulic system problem and I would check that first before pulling the engine. Yes, purchase of an engine hoist, if you have room to store it, is a very wise investment. Mine is a break down system, with the legs being removalbe for storage, and has paid for itself many times over. Les
Les Bengtson

Mike, Sounds like you need to rebuild the front brake calipers or exchange them for some rebuilt calipers. If you are not replacing your brake and clutch fluid every year or two I suggest you try working that into your maintenance schedule. Hydraulic parts will last longer if the fluids are changed each year or two.
And please get the brakes repaired, as you know a severe left pull can be dangerous for you and others.
Regards, Clifton
Clifton Gordon

Thanks Les, Clifton. I just picked up a rebuilt caliper and a slave cylinder. Nobody in town seems to have a master, so I guess I'm gonna have to hope that the car hangs on until I can get one and do the swap. It makes sense that there would be a problem in the hydraulics, given the symptoms, but it seems odd that I don't seem to be leaking fluid. The master is suspect though, and has been for a while. It's been fused with the fluid transmission pipe, so I'm having to replace that as well, but as long as I'm not having to pull the engine, I'm happy. Anyhow, I plan to change the worn caliper unit out today, hopefully making thing a bit safer out on the road. I appreciate the comments. Its always nice to hear the opinion of another party.

Mike
Mike Lord

Mike
Don't rule out a problem of a leaking axle oil seal or wheel cylinder wetting the linings of the rear causing the front to pull.

Mike
Mike Phillips

Mike

I like to drive mine on gravel and lock the front via the brake penal and the rear by the emergency brake.
Mike Phillips

Mike,

A couple of weeks ago I replaced my clutch hydraulics: it wasn't leaking externally, but the free-play became a problem. What shocked me into doing more than a 'clean and new rubber bits' was the condition of the trunnion fittings on both master and slave; both units had previously-circular holes elongated by at least 1/8", plus the trunnion pins worn about 1/3 of the way through.

Perhaps relevant to your problem, on disassembly of the old master cylinder, I found that its internal spring had broken. Given the design of the unit, this is a likely candidate in your case, too, perhaps.

BTW, don't feel alone in having one problem after another: my heater matrix started pouring coolant into the cockpit this morning so I know what I'm doing for Thanksgiving weekend!!

Best of luck.
Kevin Kelleher

Thanks Mike, Kevin. I put a rebuilt caliper unit on the passenger side Sunday evening, and all seems well with the braking now, aside from needing to turn the driver side rotor, no big deal really. As for the clutch, I'm still getting to school and to work and back every day, but I don't like the feeling of being on the edge of having enough travel to engage the gears, so that will get looked at in the following weekend, provided it gets me that far. Kevin, thanks for the advice on examining the slave cylinder internals esp. the return spring. It sounds rather convincing, especially with the condition the master cyl. seems to be in. Unfortunately, sometime earlier in this car's life, someone mangled the connection to the hydraulic piping. The nut has been it looks like threaded off camber and the flats rounded off. A master isn't too much anyway, and so I figure I'll renew the old and have a much cleaner, less suspect hydraulic system in the end. Thanks again Mike, Kevin, Les, Clifton.

Mike
Mike Lord

This thread was discussed between 14/11/2002 and 19/11/2002

MG MGB Technical index

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