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MG MGB Technical - clutch problems

hello , my clutch as been fitted for a couple of years but it as a intermittent grind ,like its catching something then it goes away .the gear changes are smooth and the clutch feel perfect untill the grind .
daz

Your problem sounds very similair to the problem that I had. Press the clutch in, and get a grinding "feel/noise". Mine started after I had replaced the clutch a couple of years prior. It would go away for a while, then come back, and then go away. I shined a light through the boot where the clutch fork enters the trans to see if the throwout bearing was OK, and it looked new. I sprayed some brake cleaner all over the throwout bearing, and the noise went away. FWIW.
E.K.

It sounds like a misalighned throwout bearing or maybe one of the securing clips has come undone. RAY
RAY

thats exactly what its doing .so you don't think ive got change the clutch thanks
daz

Mine used to grind when the pedal was fully depressed, and I could feel a vibration through the pedal at the same time. So I simply didn't push it quite as far. Eventually the release bearing broke, as for some reason one side of the casting had been rubbing on the cover plate and it had worn through. If the clutch works properly other than the noise, then the simplest thing is to leave it until something happens. I think you would be very unlucky to have some additional damage, which wouldn't have happened had you got the engine out and investigated now.
Paul Hunt

hi when you say throwout bearing do you mean thrust bearing thanks
daz

Daz-
If the pivot bushings and/or the ends of the fulcrum pin are unevenly worn, the clutch actuating fork will tilt when under pressure from the slave cylinder, causing uneven engagement of the clutch release bearing (i.e., throwout bearing, thrust bearing). This can cause a grinding sound.
Steve S.

The throwout bearing acctuates against the pressure plate when the clutch pedal is depressed. The thrust bearings are mounted on the middle main crankshaft bearing saddle to minimize the forward and reverse motion of the crankshaft. RAY
RAY

Rather than thrust bearing I'd say release bearing. Not heard of a 'thrust bearings' before, I'd say 'thrust washers' are are on the crankshaft.
Paul Hunt

"Throwout bearing" is a Yankee slang term.

"Release bearing" is a British slang term.

"Clutch release bearing" leaves no doubt as to what is being referred to.

Ain't the language barrier fun?

Now, back to the subject of the thread. Any other suggestions out there?
Steve S.

Two peoples divided by a common language. RAY
RAY

'Release bearing' can hardly be considered slang, given the full and correct description of 'clutch release bearing', a contraction maybe.
Paul Hunt

Perhaps the photo attached can demonstrate just one of the possibilities for the grinding noise you hear.

In the case of the T/O bearing in the photo, the real culprit was two broken levers in the clutch pressure plate which caused the "ring" on the pressure plate to tilt, causing the T/O bearing to misalign and wear excessively. In the photo you will also note that what is left of the carbon ring seems to have been ripped loose from the cast shell for it some time ago, allowing it to spin on the input shaft and within the shell, reducing its OD and ID to what you see. Oddly, this T/O bearing finally failed after 75K miles and looking at the cumulative damage to the bearing, it seems reasonable to me that this damage went on for quite sometime without any noticeable protest or noise that I was aware of. But it could just as well have made some real racket.

Bob Muenchausen

Bob -

Holy Smokes! I've never seen a T/O bearing destroyed like that!

I've changed clutches and found T/O bearings worn down to
1/8" into the iron casting without nary a squeek or complaint.
Daniel Wong

Yep, I have a bearing at home worn down into the housing too. I was shocked when I got a new one to fit and discovered the carbon is supposed to be sitting out from the housing!

My old GT had a clutch that made grinding noises for a little while but then it cleared up on it's own. I eventually sold that car so I have no idea if the bearing eventually failed or was replaced.


Simon
Simon Jansen

Hell, this car of mine is jinxed when it comes to T/O bearings. The one in the photo is only the second one I have replaced since I restored the car in the late 80s.

When I bought this GT in 1986, it had no clutch action, and when I took the engine/tranny out and separated them, there was even less left of that T/O bearing than what's in the photo above. The PO left me with a ring (what was left of the back side of T/O bearing case) around the input shaft and the two pivots lying in the bottom of the bellhousing with what was left of the clips. That was all!!

Apparently, this result is not as uncommon as we think, altho most end up looking like what you see in the Top photo attached here. the lower photos are of other disasters I have seen.

Bob Muenchausen

This thread was discussed between 08/12/2008 and 23/12/2008

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