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MG MGB Technical - Help!! What happened to my clutch???

Hi all. I went to my sleeping car to check on it and operate the mechanicals to make sure everything is still free and working. Well, to my dismay, something's up with the clutch. I press the pedal and there is no resistance. It feels like it is not disengaging. A few things I noted; I rolled the car in nuetral and the engine does not turn, I roll the car in gear and the engine turns. Normal. The clutch fluid resevoir is empty but no visible leaks anywhere. I figure it can be one of two things; either the clutch fluid leaked out and there is no hydraulic pressure or the clutch plate is frozen to the flywheel. Can anybody elude to anything here based on the symptoms? And, what is required to fix? I can pretty much handle any mechanical task, and would rather not pay for a tow to get it home in the spring. Thanks for all your help. -Brian.
Brian Johnson

This sounds familiar! Try putting the car in gear, get an assistant to press the clutch and roll it backwards and forwards. If the engine turns then the clutch plates have siezed together.

When this happened to me a few years ago I used the 'brute force and ignorance' method to release it. I'm not sure what others on this board will think, but it worked - apparently without damage:
1.I ensured that the battery(ies) is (are) healthy.
2.I made sure that the car was in neutral, and ran it up to temperature.
3.Now for the ignorance bit. I put the car in top gear, depressed the clutch and tried to start it.

After several goes there was a bang as the plates came free. Just make sure that you don't hold the starter motor 'on' while it is stalled in case things overheat. I don't know what damage the technique I describe may do to the started / flywheel / clutch - so get a second opinion first!

Mark
Mark Morgan

First thing to do is refill the fluid and bleed out the system. Check to insure the bleeder on the slave cylinder is closed tightly and look for leaks, that fluid had to go somewhere. This will probably cure the whole problem.
william fox

Brian. Mark is incorrect about putting the car in gear, depressing the clutch and seeing if the engine will rotate as a sign of a seized driven plate/clutch plate. He would be correct if the hydraulic system were fully functional. Yours is not. As William indicates, the first step is to fill the clutch master cylinder reservoir. Then, look for leakage from the master cylinder itself as you pump the clutch pedal a couple of times. If you find a leak, it is time to rebuild the MC. If not, proceed to the bleeding stage. You have one of four problems--leaking master cylinder, break or loose connection in the hard line from the MC to the flex hose, break or loose connections in the flex hose from the hard line to the slave cylinder or a leaking slave cylinder. Clean everything and keep an eye on it as you do you checking/bleeding procedure. You should find the problem then. Les
Les Bengtson

Thanks you all for the advice. Sounds like I will fill and bleed and watch for leaks. Followed by replacement of necessary parts. I have searched the archives, but haven't found answers to the following questions;

1) What fluid? I read some use Castrol LMA, Dot 3,4,5 and your standard red hydraulic fluid. What is best?
2) How to bleed? Some do a gravity bleed, some use and EZ Bleed, and the Haynes method What is best?

Thanks again for all the help!!! -Brian.
Brian Johnson

Brian. Fill the reservoir carefully. Wipe up any drips. Look for leaks, using a flashligh or trouble light. Pump the clutch pedal several times and again look for leaks. If you have filled the resevoir by reverse bleeding, you can no proceed to check out the rest of the system. If you have filled the reservior from the top, get under the car and go through the bleeding process. Have an assistant pump the clutch pedal a couple of times, hold it to the floor while you open the bleed nipple, you close the bleed nipple (ensuring air is not drawn back into the system) tell assistant to pump the system up again. Continute as needed, checking the reservoir every couple of bleedings. By the time you go through the pump/hold/bleed/close/release pedal process five times, your system whould be fully capable of being evaluated to find where the leak was. As to fluid, I use Castrol LMA. Be aware that if the fluids have been interchanged, it can cause the problems you currently have. In that case, pick a fluid, clean and rebuild the entire hydraulic system and reassemble. Then use you choice of fluids and bleed. Rather important to know exactly what is in the system before you ever add any to it. Les
Les Bengtson

Brian,

To expand a bit on Les's excellent advice, LMA (which is D.O.T.4) is a good choice. But by all means stick with D.O.T. 4 for glycol-based fluids (Castrol LMA is a glycol-based fluid, as are all D.O.T. 3 and 4 fluids) or D.O.T. 5 for silicone-based fluids. Glycol fluids can be intermixed (but you don't want D.O.T. 3....) but glycol fluids cannot be mixed with silicone fluids. DO NOT use a mineral-based fluid (i.e. standard hydraulic oil). It will destroy your seals in short order. What you want falls into the class of what's commonly called "brake fluid."

So to help clarify the water I just muddied, you want either D.O.T. 4 (like Castrol LMA) or D.O.T. 5 (but ONLY if that's already what's in the system -- unlikely but possible -- or you have completely and thoroughly flushed out every last trace of D.O.T.4 and rebuild ALL of the components.)

As to which is better, that's somewhat of a religious war here with strong adherents on both sides. I won't state my view but to say I have seen both fluids give years of trouble-free service when maintained properly....

HTH!
Rob Edwards

This thread was discussed between 24/02/2002 and 25/02/2002

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