MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Unsolved Clutch Issue

Thinking that my clutch disc was rusted to my flywheel I have removed the gearbox from the engine in order to remove the clutch assembly. After removing the clutch assembly from the flywheel the clutch disc fell to the floor with no evidence of ever being rusted to the flywheel.

Totally bewildered, it occured to me to observe how the assembly functioned. Simply put depressing the clutch pedal causes the release bearing to depress the "top" pressure plate, which causes the release of the "lower" pressure plate, allowing the clutch disc to spin freely. So, the pressure plates move in opposite directions; toward eachother to disengage the clutch and away from eachother to engage the clutch.(Please excuse my inaccurate terminology)

When bolting my clutch assembly to the flywheel there is significant movement of the pressure plates. So...

Should the lower pressure plate extend beyond the housing of the clutch assembly?

Is it possible to adjust the pressure plate system to accomodate a new and/or worn clutch disc?
gerard hutchinson

It sounds like everything was correct unless the friction disk was in backwards, it should be stamped flywheel side on one side, the hub with the springs should face away from the flywheel. As the release bearing presses against the fingers of the diaphram spring in the pressure plate housing the outer ends of the spring pull the steel clamping plate back, this releases the clutch friction disk to spin free. It just looks strange as at first clance it would appear that the release bearing pushes the together. The fingers on the diaphram spring will move quite a bit when you bolt the assembly in place.
J Heisenfeldt

J,
The friction plate was in correctly and nothing else seems to jump out as a problem.
gerard hutchinson

Back to your first note, apparently your assumption was wrong about the disc being rusted in place. So the question gets back to why it didn't release. If the problem was deficiency of hydraulic operation, it would be an easy fix not requiring removal of the engine.

Follow up questions: Was the clutch working sometime in the past before you had this problem? Did the problem occur after long term storage, six months or more (could be hydraulic failure)? Did this problem occur immediately after reassembly of clutch and engine to gearbox (could be hydraulic or maybe the clutch disc was in backward)?

If the clutch disk is installed backward the central spring hub will foul on the flywheel bolts, and the clutch will not release.

Another possibility. If a new spigot bushing was installed in the crankshaft, and teh bushing was undersize or maybe deformed during assembly, it could bins on the gearbox input shaft. In that case the input shaft will continue to turn with the flywheel even when the rest of the clutch is working properly, and it will act like the clutch does not release.
Barney Gaylord

Gerard, I am with Barney on this one. The bleeding of the clutch is often the cause of this type of problem.
The problem seems to be that air sits in the slave cylinder when it is bled unless the piston is pushed fully in.
Best is to open the bleed nipple then push the piston fully in and then secure it with a strap or clamp so it will not move. Then bleed in the normal way.

Neil
Neil Purves

Barney,
The car I am restoring is completely from the ground up and has never run. All of the hydraulic components are new or professionally rebuilt. So the clutch has not had the chance to "work." The clutch was install 9 - 12 months before the hydaulic system was filled with fluid.

I am certain the clutch disc was installed in the correct position. I did not install a new spigot bushing and I have not inspected it to determine if it was deformed (I will do that this weekend).

I have bled the clutch several times and there does not seem to be any air but I will try it again with the piston depressed.

If the clutch cannot be adjusted then is it posible that the release bearing is not making contact with the clutch? Could the push rod be too short?
gerard hutchinson

I would not rule out the disk being reversed. I have done it myself at least once, even when I was being careful and was sure it was right.

When the clutch does not release, the first thing to check is travel of the slave pushrod. Get under the car and watch the pushrod and release lever as a helper will push the clutch pedal. Full travel of the pedal should produce about 5/8" travel of the slave pushrod. If you don't get at least 1/2" of travel at the slave, you have a hydraulic problem, usually air in the line, sometimes a sticky master cylinder piston, or perhaps a master pushrod adjusted too long preventing full return of the master cylinder piston.

The trick to getting air out of the clutch pipe is to push fluid through quickly and continuously to push any air down the pipe along with the fluid. Slow bleeding allows air to bubble back up the pipe and remain in the system. Pressure bleeding should always work. Reverse bleeding can also work. See here fore more information: http://mgaguru.com/mgtech/hydraulics/ht106.htm
Barney Gaylord

This thread was discussed between 19/05/2008 and 20/05/2008

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.