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MG MGB Technical - Clutch problem

I've developed a clutch problem today on my 73B Roadster. I was driving along just fine for about a 1 hour out in the great weather drive when all of a sudden the clutch pedal started getting closer and closer to the floor. Eventually it was down so low that I couldn't completely disengage the clutch...........or, needless to say, change gears. I nursed the car home, turning it off at stop lights and putting it in 2nd. Then when I started the car when the light turned green the car would roll forward even with the clutch completely depressed. So, as you can see, it wasn't completely disengaged. I could change gears when rolling over 30 though so managed to get it home.
This past Tuesday I had the car in to a mechanic (British car guy) who took the intermittant click/click out of the clutch pedal. He replaced the top small linkage pin (about 1/4" in dia x about 1" long) that had significant grooves worn into it. Not knowing what the click/click problem might be I also had the new large pivot bushing on hand, so he put those in as well. I think these mount lower down on the pivot arm.

I expected to find his linkage pin fallen off when I took off the brake/clutch cover, but that was not the case.

Before I headed home after the problem developed I looked in the clutch fluid can and found it was about 3/4" low. I topped it up and drove home. When I got home is was about that same 3/4" low again.

So, do you think I have an "air in the line" problem, a leak or perhaps something else that was agravated by the work the mechanic did?

Thanks,
BH Davis
BH Davis

It's leaking from the linkage side of the slave cylinder....from the rubber protective cup.

Rebuild kit time?

BH Davis
BH Davis

BH, It may be a good idea to disassemble the slave and inspect it before you order a kit. The ones I have checked are usually pitted too badly to rebuild. Hope yours is good because the kits are cheap, cylinders aren't.

Clifton
Clifton Gordon

Clifton,

I pulled the slave cylinder and took it apart. There was some pitting on the cylinder walls and a small tear in the rubber cylinder cup.

I went to CarQuest and they had the 1 1/4" cylinder cup. I then took 400 grit Emory paper and wrapped it around a small brush that I had mounted in a drill. A few minutes of honing with the 400 grit paper and I put the whole thing back together.

I had thought my weekend of great MG weather was going to be wasted!! However, with the slave cylinder mounted back on the car I took an hour ride in the country with a perfectly working clutch this afternoon!!!

Thanks for taking the time to give of your time and experience on this forum.

BH Davis
BH Davis

BH, Glad you got it going without major problems. I appreciate your kind comments.

Clifton
Clifton Gordon

BH

I'm more impressed with the fact that you appear to have managed to install the slave and bleed the system without any drama. What is your secret?

Regards
Roger
Roger T

Maybe I just don't know enough to have recognized the problems!!

Actually, I've always said......"I'd rather be lucky then good!".

BH Davis
BH Davis

Buy a lottery ticket! I kid you not.

Regards
Roger
Roger T

I have a similar problem to BH Davis. My clutch on my '73 MGB became stuck engaged last Thursday evening. I looked at it moments ago to see if the slave cylinder was moving with clutch pedal movement. It was. Fluid in master cylinder appears to be a little low (any idea on what kind of fluid I should replace it with?) Second question: Is there a spec on movement of the slave to disengage the clutch? With engine running, the clutch pedal vibrates when depressed and no gears can be selected. Any help would be greatly appreciated.

Regards,

Dave
Dave B

Dave,

Once I got the slave cylinder working again I was surprised at how little it moved back and forth to work the clutch. If yours is moving about 1/2" then that is a pretty good match to what mine is doing. Mine is working fine now.

I used Dot3 brake fluid in mine after several people told me that was the correct fluid.

BH Davis
BH Davis

Mr. Davis:

Thanks for the info on the movement. It appears to be moving about 1/2 inch or so. I'll pick up some Hydraulic fluid tomorrow and top it off just in case I need a little more movment. It was really weird when the clutch failed to disengage. It happend all of the sudden.

Thanks,

-Dave
Dave B

Dave-
The vibration is a bad sign - means the pressure plate/release bearing is near or just past death. Plan on a clutch job.
FRM
FR Millmore

Whilst Dave's fluid level may be a little low (when did you last check?) it would have to be down to the bottom inch or so to affect clutch slave travel, and you are getting the correct 1/2" to 5/8" so topping-up is very unlikely to change things. With the vibration it sounds more like a catastrophic failure inside the bellhousing, so is an engine-out job.
Paul Hunt 2

Thanks to all for the help on this one. Deep into a clutch replacement at the moment. Both the slave cylinder and the clutch were toast. Slave cylinder was leaking hence the low fluid level. Hopefully be back on the road sometime next week!

-Dave
Dave B

This thread was discussed between 25/05/2007 and 06/06/2007

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