Clutch noise debugging

[foamcar]

The noise: low to medium pitched "howl" when clutch pedal depressed

The parts: 519 transaxle in 55 coupe, S90 engine with 200mm disc and pressure plate, diaphram plate with collar added to work with early throwout bearing.

Diagonosis to date: Removed engine, pressure plate, throwout bearing. Disc is 8.8mm thick free and about 8.4mm under pressure(spec is 9.5mm I believe), throwout bearing appears and sounds okay. Under load I hear no noise or roughness. A few magnetic fillings in bell housing, which could have been there prior to this setup installation 2 years ago. Flywheel depth is about .5mm shallow as if the disc surface has been ground down a little. No signs of metal rubbing except the outer large ring of the collar is marking the sping fingers, but not gouging them. Based on these marks, I'm thinking my home made pedal stop is not properly adjusted, allowing the pressure plate springs to get compressed too much, but what is causing the noise? Throwout bearing contact surface and collar contact surface look okay to my untrained eye.

This noise did not exist with the PreA engine with 180mm clutch. So the different parts are the flywheel, gland nut, pressure plate and disc(used from car S90 engine was in(Fomacar). The gland nut has the bushing and was properly lubed during installation. Noise did not exist with this engine and clutch system(less collar) in 63 T6.

[MoPor]

I can hear my to bearing howling and squeaking when the clutch pedal is depressed. After it warms up it quiets down. I have no other idea what else it could be.
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Matt

'58 356A coupe
'00 Boxster S

[ensys]

Mr. Foamcar:

Just spitballing here, but I have questions:

1. What is the nature of the particles in the bell housing? (small chunks, filings, strand shards, etc.)
2. Did you examine the collar?
3. What does the fork look like?
4. Can you swap out T.O. brng. for another? Does old one move freely?

Just curious.
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Keep 'em flying...

S.J.Szabo

[foamcar]

An update:

First, the particles were very small, like file shreds, and as I said, could have already been there. The fork appears fine, with no slop of the throw out bearing.

I disassembled the throwout bearing and examined every ball and the races. All looked fine. Re-greased and assembled. The contact surface was not flat, nor was the collar contact surface, so that has been rectified.

I believe the root cause is overtravel, as there are marks from the outer collar rim(not the contact surface rim) being made on the diaphram springs. The only way that can happen is from excess travel. I called Kennedy Engr. who makes the collar, and they verified overtravel. Could not explain the noise unless it was caused by undue high pressure on the throwout bearing. I think it could also be possible from the collar adapter rim contact with the springs at 800 rpm.

I had to fabricate a pedal stop, as the PreA has none. I will adjust it further upward and for sure check for overtravel this time. I will report back results, but first the transaxle is coming out for new front mounts, new flex brake hoses, new seals, replace missing oil slinger, etc. in prep for a long trip to Boston in August.

Phil Planck

[roy mawbey]

Phil,

I presume this noise is like a screeching noise as the clutch pedal is released after changing gear from one to another. I have experienced this myself. I disliked the original 180mm diaphragm clutch in my A and changed it for normal lever plate spring version. The clutch action has since been perfect for many years now but I have had this screeching noise which I could not establish the cause. But I have found a way to stop it.

The last time I removed the engine I changed the release bearing as I suspected this was the problem, I lubed the flywheel gland nut bushing (since bought a new one but not yet fitted it ) and inspected the face on the clutch where the release bearing contacts. All looked okay.

The noise was still there after doing all this. I noticed however ( don't laugh ) the noise seemed worse when the car was left for week without driving and if the weather was very damp.

I have now found a cure! I start the car, depress the clutch pedal half way down in neutral and allow the release bearing to run up to speed for about 5 or 6 seconds before then engaging gear and moving off.

This stops the noise from happening. I had the feeling before I did this, either the gland nut bushing was worn out, or the pivoting action of the release bearing was not happening correctly. I cannot be sure from memory that I lubricated the two ears on the bearing which swivel in the arm.

For sure I thought putting a new release bearing in place would correct it which it didn't.

Although it sounds like a dry bearing who knows??
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Roy
RHD356A super75 106954