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MG MGB Technical - Stupid Clutch Question

Hello,

I know there are hundreds of threads on clutch issues, but let me ask this one anyway.

My car is a 1973 MGB. The engine was rebuilt and at that time all new clutch parts were installed, about 6,000 miles ago.

The question I have, is whether the clutch is adjustable? I know that it is hydraulic, but lately it "seems" that the pedal has to come out more before the clutch engages. Otherwise the clutch works fine.

Is this adjustable? If so, how/what is the procedure?

Thanks,

Robert
Robert Browning

It is not adjustable, but you may want to look at the mechanical parts of the linkage for wear. the pins get worn and the holes get elongated which causes excess free travel in the system. These conditions normally result in a low pedal rather then a high engagement point. One possability is that the piston in the clutch master cylinder is not returning completely, this prevents the pressure in the line from being released into the resevoir. Pressure builds in the system from heat and can partialy release the clutch which could result in your high engagement point. If it is higher when the car is hot compared to when it's cold, I would check the master cylinder for proper operation.
John H

Your clutch sounds fine. With a new clutch, there are irregularities in the disk surface. These irregularities contact the flywheel/pressure plate surface and begin the engagement with the surfaces relatively far a part and the clutch pedal closer to the floor. As these irregularities wear off, the distance between the surfaces lessens prior to engagement and the pedal gets higher. With the surfaces true and a non-spring disk (some disks have springs between the two friction plates) the pedal should be almost it the top prior to engagement.
Lee Bradley

Hey Robert,
Just had about the same problem on my 72. Also had some leakage I think, although the oil pressure line was leaking. I rebuilt the clutch cylinder with a kit and now the clutch engages very quick, in fact maybe a little too quick, but I will get used to it.

Lotsa luck.
JH
James Huggins

Wear in the mechanical linkages at the pedal end causes the clutch engagement and disengagement point to get *closer* to the floor. The design of the hydraulic system takes account of any wear in the linkages and plates at the clutch end and this is not apparent at the pedal. If the engagement and disengagement point is getting higher that indicates wear of the friction plate, cover plate and flywheel, or possibly weakening of the diaphragm springs, as all these result in less pressure on the friction plate and hence it will start to slip with a smaller movement of the release bearing.

John H makes a reasonable point about the master piston not coming back far enough to clear the bypass port and so pressure from heat developing to partially release the clutch before the pedal is operated, but unless the pedal is physically preventing the piston from coming back far enough the return spring in the master cylinder should always push the piston back even if wear in the linkages at the pedal end mean the pedal isn't pulling it back as far as it should.
Paul Hunt

Maybe your system had a bubble in it before, and it finally worked its way out. And maybe the seals are sealing better now they are being broken in. I have felt differences in the way the hydraulics work in hot versus cold temps, too.

At least it doesn't sound like a big problem at this point, as long as there's no slipping.
Tom

Thank you to everyone. I feel much better now. The car is not driven a lot and I think that maybe it is just getting to the correct height. Also, it may just be me.

FYI - All the linkage parts were replaced with new ones when the engine was rebuilt and the new clutch and O/D transmission installed, so I do not think it is from parts wearing.

As usual, I do eppreciate everyone's help on this site.

Thanks,

Robert
Robert Browning

Sounds normal.

The clutch pedal disengagement-engagement
height position always migrates upwards soon
after I do a clutch change before leveling off.

I think the new clutch plate springs and hydraulics
have to be worked a few times to allow them to
settle in to a certain position after being freshly
installed.

Daniel Wong

Wear in the linkages or on the clutch friction surfaces has absolutely NO impact on the pedal travel or bite point!

The hydraulics are totally self adjusting.

Any variation is caused by air in the system or the hydraulic pistons sticking or hitting the end stop (master only)
Chris at Octarine Services

I have to say *terminal* wear in the clutch friction components i.e. when it is at or very close to slipping in top gear *does* impact on biting and releasing point, Chris, making it higher. This comes about because as they wear there is less tension from the cover-plate springs, which means less pressure is needed from the release bearing to cause the clutch to start to release, hence less travel from the pedal. But you do have to go a long way towards clutch replacement before it comes noticeable.
Paul Hunt

This thread was discussed between 07/08/2008 and 12/08/2008

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