spinaker

I have been trying to diagnose a bearing sound coming from behind the driver side TB cover of my '85S. One mechanic told me that it was likely the A/C compressor bearing and another told me it was the viscous cooling fan bearing. Using a stethescope I'm convinced it is from behind the TB cover and I have now had all of the belts off and confirmed no other bearing sounds.

What is potentially making this noise? How much work is it to take enough off of the front of the engine to diagnose the problem? Is that the right approach? I am not confident enough to take the belt off and retension it if that is required to repair it. I may be confident enough to take things far enough apart to diagnose the problem and would prefer to have a clear diagnosis before taking it to a mechanic.

TB was replaced two years ago (15,000 kilometers) and retensioned one year ago. When the TB was done, the invoice states that cam belt roller, tens roller, tens boot, tens bushings, tension roller, cam belt roller, belt and two crank seals were replaced as well as water pump. I got a box of the old parts when I picked the car up but have since thrown them out.

The TB tension light is not on and has never come on since the belt was replaced. There are no oil leaks anywhere.

Suggestions?

wds928

Is it a bearing noise? I had an intermitttent noise on mine, removed all the accessory belts to eliminate them. Turned out to be the waterpump bearing on mine. I replaced the water pump, timing belt, cam sprockets, tensioner roller, idler roller and rebuilt the tensioner. My first time doing this job that took too long (about 30 hours in all), but definately a worthwhile project for those inclined.

Was a new or rebuilt w/p installed? Good luck.

WICruiser

The drivers side is where the power steering pump resides (high) and the alternator is low. I am not sure but it sounds like you have discounted these by removing their respective drive belts. The A/C compressor is on the passenger side down low so unless we have the sides confused it seems like the mechanics diagnosis was way off base.

The upper timing belt cover on the drivers side is a bit of a pain to get off if I recall, mine is off my '85 right now but I am in the middle of a major clean up and restoration project so I removed a lot of the stuff that I think might be in the way. The only thing behind that cover is the timing belt and the camshaft sprocket if I recall correctly. Most of the things that could be making the noise are behind the lower cover which requires removal of all of the pieces and parts in front of it.

Maybe we should start at the beginning, what makes you think it is a bearing noise - or maybe easier - what type of noise are we trying to diagnose?

spinaker

The noise I'm hearing is a rattling sound. Its not intermittent. I'm quite sure its a bearing sound or at least a sound from something rotating.

One thing I haven't checked is if something is loose. Covers, distributor....is there anything else there that could be rattling? Could it be something this simple?

When I use the stethescope to locate the source, the loudest sound comes from the drivers side TB cover.

Is there any kind of a bearing associated with the distributor?

airosey

My 81 was making a sound like that at SITM, and turned out to be a loose timing belt. I would check your tension. Could possibly be a waterpump too. Before my tb/wp job, the waterpump was rattling like crazy, but by that point it was leaking coolant too.

Big Dave

Any chance your ignition rotor is loose? I had a rattling noise when one of mine wasn't tight.

killav

Could be the dreaded chain tensioner on the passenger cylinder head. You could pull the valve cover and diagnose this prior to sending to your mechanic. You could probably start the car for a very short duration so that oil doesn't get everywhere and give it a look/listen.

Edit: I just re-read and you stated that the drivers side was the loudest source. Not passenger.

Mike
1987 S4 Auto

Big Dave

Hell, I have a video clip of a chain tensioner failure....just search for threads started by me. You should be able to eliminate (hopefully) that possibility fairly easily by listening to the clip.

algie928s4

Funny enough I had a similiar noise, bought the stethescope, still convinced same as you- turned out to be the A/C compressor.
At this point I take no responsibilty for my 2 cents, any advice / comments are based on personal experience and as such I refute any future claims by you for a new engine!
LOL 928 owners are always easily identified by their constant twitch and their close proximity with their wallets, be an optimist but a carefull one!

spinaker

In replacing all of my drive belts today I noticed that the smog pump bearing is rough. I'm pretty confident that is the source of my bearing sound. I suspect it was compounded by the fact that two of the belts (AC and PS) were quite worn and not properly adjusted. Engine is much quiter now.

Question: How easy is it to repair this bearing? Can it be replaced without replacing the smog pump?

I know I will get suggestions that I remove the smog pump. I still have the original cats. If I was to remove the smog pump, what else is affected and what else should I consider removing? I'm reluctant to start the emissions removal exercise as the car runs extremely well right now.

Disclaimer: Concepts discussed in this thread are theoretical. Any discussion does not imply intent or contemplation of illegal or less than environmentally responsible actions.

figgen

Doug

I "theoretically" removed my smog pump, air line and cats and had a custom x pipe built "for track purposes". If you want it. I think it's in my shed some where. At the time the bearing seemed fine. Heck it may even be a good trade for some of your advice on the motor mount replacement I'm contemplating.... and you have completed

Shoot me a PM if your interested and I'll check for it.

heinrich

There is a bearing inside the water pump. Does it run true?