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-:vw:-
08-15-2010, 08:16 AM
Hi guys,

First time post but I've been lurking and reading for a while now, great forum. I had a question regarding the accessory belt and tensioner on my recently acquired 99 A4 Avant.

Here is a link to the info on the car:
http://forums.vwvortex.com/showthread.php?4917207-FS-Pre-Facelift-1999-Audi-A4-Avant-1.8t-Quattro-5-SPD-quot-Audi-Tech.-Owned-quot-166k-CT&p=66565048#post66565048

Now... The P.O. did a fantastic job on this car it's in great shape and drives perfectly however about 2-3000 miles after his rebuild I shredded the acc belt:
http://i614.photobucket.com/albums/tt229/kev5k/SNC00073.jpg?t=1281885470

Now... the P.O. said this was replaced during the rebuild and I'm going to have to go with him on that as the belt looked pretty damn new when I pulled it off. I checked all the associated pulleys for seizing and there was none. I looked everywhere for something coming into contact with the belt and this is the best evidence I could find:
http://i614.photobucket.com/albums/tt229/kev5k/DSCN2062.jpg?t=1281884677

A/C tensioner with bracket with some pretty evident rub marks on it as well as a nice gouge out of the aluminum. My question is this. At what milleage does the acc belt tensioner need to be replaced? The engine he swapped in had 50-60k on it at the time of the swap. Is it possible that the belt was "spinning out" and contacting that tensioner bracket at high rpms due to an aging belt tensioner? The positioning of the A/C tensioner and rub marks line up EXACTLY with the front side of the belt that I lost. If not is it remotely possible that something hopped up on the highway and contacted the bottom of the belt causing the damage and that the marks on the tensioner are just the after effect of the belt breaking loose? The car has no belly pan so... I suppose it's possible. I have ground down the side of the tensioner that had the rub marks but I doubt that will have much if any effect as it definitely wasn't a constant rubbing issue. There is plenty of clearance between the belt and the tensioner bracket from what I can see unless the belt is "spinning out" so to speak and contacting it under load. I am keeping an eye on the new belt and have yet to see any signs of rubbing but will continue to monitor it so I can find out what may be going on. Any thoughts you may have are appreciated.

Thanks

walky_talky20
08-15-2010, 09:19 PM
Hmm. That's kind of weird. I'd just keep an eye on the new one and check for any abnormal wear.

I've got another accessory belt "puzzler":

A few weeks ago a Jetta TDI came into the shop with a "belt squeal" complaint. Everything else was fine, car drove fine except an accessory belt squeal on accel. I took a look at it and the pulley on the alternator was *completely gone*. It wasn't even there anymore, just the shaft coming out. I have no idea how that happened, as you need a special tool to get the VW alternator pulleys off anyway. The owner said he ran over something. I think he just ran over his own pulley! Interestingly, the belt wasn't damaged bad at all, and the charging system continued to work fine, the tensioner just took up all the slack.

The guys in the shop were trying to think of what exactly you could possibly run over that would loosen the bolt and pull the pulley off the shaft, all in one motion, without even touching the belt. Needless to say we didn't figure it out.

k0mpresd
08-15-2010, 09:21 PM
Hmm. That's kind of weird. I'd just keep an eye on the new one and check for any abnormal wear.

I've got another accessory belt "puzzler":

A few weeks ago a Jetta TDI came into the shop with a "belt squeal" complaint. Everything else was fine, car drove fine except an accessory belt squeal on accel. I took a look at it and the pulley on the alternator was *completely gone*. It wasn't even there anymore, just the shaft coming out. I have no idea how that happened, as you need a special tool to get the VW alternator pulleys off anyway. The owner said he ran over something. I think he just ran over his own pulley! Interestingly, the belt wasn't damaged bad at all, and the charging system continued to work fine, the tensioner just took up all the slack.

the alternator pulley on my wifes jetta tdi came off as well. it made a squeaking noise, then a knocking noise she said on her way to work. then came completely off on the way home. thats pretty crazy about the belt still being on the shaft though.

walky_talky20
08-15-2010, 09:39 PM
the alternator pulley on my wifes jetta tdi came off as well. it made a squeaking noise, then a knocking noise she said on her way to work. then came completely off on the way home. thats pretty crazy about the belt still being on the shaft though.

Wow, thats crazy. These things must have a problem with coming loose then. Must be *all that torque*.

thom
08-16-2010, 12:56 PM
The alternator clutched pulley failure is pretty common on the MKIV TDI. Mine went at about 4 years and 90k.

-:vw:-
08-16-2010, 03:21 PM
Aren't the MKIV pulleys in question plastic?

thom
08-16-2010, 10:41 PM
No, not plastic. Might as well be, though.

walky_talky20
08-17-2010, 10:24 AM
There is a plastic idler in the system, but the failure in discussion is the disappearing alternator pulley, which is metal.