Lotus Elan

Clutch Screeching Noise - Solved

PostPost by: 65 Lotus » Mon Jun 08, 2015 7:16 pm

After pulling the engine (again) I finally determined the cause of the loud screeching or chattering noise I get when depressing the clutch, usually only the first few times when cold.

The throw-out bearing thickness is very close to the thickness of the stationary hub onto which it is pressed.

If the TO bearing has ANY ability to rock whatsoever (and I have two that do, including a new one), the clearance between the bearing and hub is small enough that positive clearance is lost between the stationary TO bearing hub and the inner edge of the rotating pressure plate contact patch.

Contact then causes the entire fork to chatter which in turn causes the bearing retention spring clips and link parts to go nuts and chatter wildly, sounding off as a loud screeching sound.

If the condition exists on your installation, before installing your next TO bearing mill down a bit of the face of the bearing retainer hub to provide enough clearance such that contact between the hub and the pressure place is not possible, say 1 mm. Be sure to chamfer the edge to make the TO bearing re-installation go smoothly.

Obviously not the only source of a clutch screech, but it was the issue on my Type 26 S1 s/n 1918. Apologies if this has been discussed elsewhere; couldn't find anything.

Scott in Ohio
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PostPost by: gjz30075 » Mon Jun 08, 2015 8:00 pm

Good to know. Thanks Scott.
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PostPost by: rgh0 » Tue Jun 09, 2015 8:54 am

There is a no name brand ( chinese?) thrust bearing on the market which has a brass inner sleeve section that may also cause this problem if it contacts the thrust pad on the clutch pressure plate. The FKC brand ones (Japan) that I have used for many years have a hard black plastic inner sleeve section which would not cause the problem if it hit. It is also further recessed so probably would not hit the pressure plate pad in anycase.

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PostPost by: cal44 » Tue Jun 09, 2015 10:37 am

Thanks Scott and Rohan..........timely tips indeed.


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