'91 100q Alternator Belt Screech & 400-500rpm Idle Speed

[Fred Munro]

There are a few things to check.
Are you using a metric V-belt (i.e from the Audi dealer) or a SAE belt from
your local FLAPS? Metric V-belts use a different numbering system than SAE
V-belts and some metric cross-sections cannot be matched with SAE belts.
There are cross-references available to match up belts, but before using a
SAE belt you should check for differences in length, cross-section, and
ride-out. I had a squealing problem with my first Audi ( an '86 5000tq) and
solved it by using metric belts from the dealer.
If a V-belt is worn, it can get narrow enough that it bottoms out in the
pulleys - if the top of the belt sits below the outer edge of the alternator
pulley it may be worn too much. 
Check for wear on the pulleys. Pulleys don't last forever and these cars are
getting enough hours on them that the pulleys may be losing their profile to
wear.
Are all the pulleys aligned in the same plane? If one pulley is cocked at an
angle (i.e. the alternator mounts allow it to twist a bit) the belt will
squeal and wear.

HTH

Fred Munro
'97 S6

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of wadd-wadd at usa.net
Sent: Monday, September 17, 2012 9:37 PM
To: quattro at audifans.com
Subject: '91 100q Alternator Belt Screech & 400-500rpm Idle Speed

Two issues with my '91 100q

-the alternator belt lets out an embrassing screech every other day
regardless of how much I tighten it. Any way to address this? Any special
belt or dressing?
-the idle speed is about 400-500rpm. The car doesnt stall though.

Thanks!

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