[s-cars] Subject: Serp belt woes

[Aaron Ryba]

Thanks everybody for the input.

When I ran the car without the tensioner I mean I removed it and the serp belt so no accessories were running, only the timing belt. I wanted to make sure it wasn't the TB tensioner/bearing which it wasn't.  What is weird is that I also ran the engine without the TB cover but WITH the tensioner and belt and the same noise persisted. The noise which I thought was the sound of the tensioner roller rubbing against the TB cover (wear on the cover to prove it) persisted without the cover. I didn't put a stethoscope on anything but I am fairly certain the rumbling noise is coming from the tensioner bearing and not the other pulleys. I'll try the DIY stethoscope with some rubber tubing this weekend. I haven't yet tried to freely spin the other pulleys, I know the steering pump is spins well, it could be the AC compressor. I'll have to look when its not snowing outside. I would describe the noisy compressor when running to be like a "jet
engine or turbine sound," so it seems like it is failing like others
typically do.

With the serp tensioner out of the car the bearing roller turns just fine and without noise or problem and there isn't any play in it. It will turn about 4 or five times with the spin of my hand. The reason why I think it is a belt problem is because the tensioner seems to be fine. The spring is still very firm as evidence by how much force is needed to lock it into place for removal. From reading in older posts it seems like when tensioners fail it is the bearing and not the spring. I assume a sticking bearing will improperly load the spring and hence the cracking noise.  I agree that even with a stretched belt, the slack would be taken up with the tensioner however the cracking noise from the spring in the tensioner only happens when under load from idle when doing a three point turn or pulling away from a standstill so perhaps it is only at these moments of low RPM when the slack in the "stretched" belt is enough to overcome the tensioner spring. It
 seems like when the RPM is raised there is more tension on the belt and hence the cracking noise goes away. I don't know if that even makes sense. Oh well.

The secondary scraping rumbling noise (i assume from the bearing itself or from rubbing against the TB cover) happens all the time and is loudest around 2k rpm. Not a very loud noise but noticeable even from inside the car. These noises all seemed to gradually get worse over time,  and the fact that I started to use the AC over the summer for the first time since I replaced the tensioner and belt makes be think it is the AC which ruined the belt. Due to the AC compressor not being totally seized but just harder to rotate maybe it is possible that put the undo stress on the belt gradually which would otherwise have heated up and shredded had the compressor seized up instantaneously. 

I guess the cheapest solution right now is to throw on a new belt to the tune of about $25 and keep my fingers crossed. If that does it I will keep the AC off till I can fix that. The non-AC spec belt is a good idea, I thought of that as well but being in SC here for the summer I'd rather pay for a new belt every year than go without the AC, granted the compressor lasts much longer that is!

All this typing and I could have already replace the belt by now.

Aaron Ryba
noisy 95 S6

----- Original Message ----
From: Tom Winter <tom at freeskier.com>
To: s-car-list at audifans.com; aaronryba at yahoo.com
Sent: Wednesday, January 16, 2008 10:00:30 PM
Subject: Subject: [s-cars] Serp belt woes


Aaron - I'm no expert, but I'd expect the tensioner to last longer than
that. I did have some noise issues from a serp belt, not a rattling,
 but it
was making noise (and then broke, solving the noise problem! LOL!).

Perhaps you'll get lucky on this one and it will be just the belt. You
 said
you ran the car without the tensioner - I'm not sure how you did this -
 and
there was no noise under these conditions. But I'm wondering if the
 other
pulleys in the system aren't worth taking a close look at. Perhaps when
 the
belt is under tension, they are the source of the problem. Just a
 thought. .
.

Good luck.

Tom
'95 S6 Avant, waiting on parts







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