sweet928

79 ob 5 speed making a sort of alternator noise when cold in the cold. Only when clutch is pressed to floor and gets louder and faster sounding with engine revs. Goes away when releasing clutch and not at all in neutral with foot off clutch and reving engine. No noise when in gear at any revolution. Then went away after driving for 15 minutes. No fluid on ground. Too dark to check fluid level. Guessing low clutch fluid which expands to minn level when warm. But wondering where the fluid went to loose the level. ... Any other ideas on possible issues.

The Fixer

Throw out bearing, you could determine this by trying a little Wurth high Pressure Grease Spray lube in a can.
Are you familiar with this German product? Great stuff. Goes into the tightest area and becomes high pressure grease.
When i had my bell cover off i used it in my throw out bearing bearing just to add some more miles..

If you caught it early, which you did, and it is the TO bearing; Wurth stuff or similar product may correct it for a pretty long time.

That's a beautiful Petrol Blue Porsche you own.

I noticed it replying to the "how old are you" Insurance application thread.
matt

dprantl

Actually, it could be the pilot bearing. When the clutch is not pressed, the pilot bearing inner and outer portions are spinning at the same speed, meaning the bearing is doing no work. When you press the clutch, the outside portion spins with the crank and the inside portion in contact with the clutch shaft stops spinning, meaning the bearing is getting a workout.

Dan
'91 928GT S/C 475hp/460lb.ft

The Fixer

I think you may be right, re-reading the title of the thread "humming and buzzing" sounds more like the pilot than TO.

WallyP

Agreed - sounds like the pilot bearing.

sweet928

How big of a job is it? Under the car stuff is something I leave to my trusted mechanic. He estimated @4 hours. Are parts still available for MY? Safe to drive a little until my appointment next week? Also, why does the noise go away when warm?

sweet928

Looked up on Pelican and seems Pilot bearing is quite cheap. Is there a "better" one I should consider? Supplier? Brand?

sweet928

Thanks for your help and kind words on my OB. It was the color that sold me when I was on the hunt. Never saw the color before and "had" to have it when I pulled up the the PO's house. Funny as I "hated" cork color in my youth but now love it with the Petrol blue paint.

tailpipe

Pilot bearing are cheap, you can buy one locally at any bearing shop its a standard bearing or buy one from our suppliers here. The clutch and related gear all come out through the bottom cover. You might not even have to drop the exhaust depending on how its set up. Replacement should not take more than 2 hours. I have done one in 1 hour but I had extra hands helping with tools. If its an original bearing it will be stamped with the Porsche name and number. If you knock the center out, the outer ring makes a cool Porsche key chain....

The Fixer

Yes, Porsche has always had great colors,
I briefly owned a 911SC in Petrol Blue with Black interior. Always loved the color but found a Carrera that had similar color..

You should consider replacing the TO bearing while your mechanic is in there.

Matt

69gaugeman

I was the same way with that exterior/interior colour combination until I bought my Touareg with it.Now I love it.

sweet928

I have not been able to duplicate the noise. Is it normal for the "pilot bearing" noise to stop? The car had sat for two weeks.

dprantl

A failing bearing may or may not make an audible noise. It may make noise when it is cold, and not when it is warm. The only way to know for sure if the pilot bearing is bad is to remove the clutch pack and inspect it directly. If the pilot bearing really is bad and you ignore it, there is a tendency for it to eventually weld itself to the crank making replacement a real bear. Removing the clutch really is not too difficult of a job on a 928.

Dan
'91 928GT S/C 475hp/460lb.ft

sweet928

Thanks. I'll have my mechanic check it out this weekend.