AC and alternator belt help plz!

[rackley]

I have a 91 Jetta Diesel with a TD transplanted into it.  

I'm having an absolute hell of a time getting the AC and Alternator belts working right.  

I've tried Goodyear, NAPA, OEM, and now even the $15 Gatorback belts.  They all do the same thing - I tighten them down to spec, then they flap around when the car runs (even when tight!  very strange!), then they just stretch out until they're about to flap off.  So then I have to adjust the tension on both, and after about 2-3 adjustments there's no adjustment room left on the alternator pulley.  At this point the belt just keeps getting looser and looser until it squeals and then eventually just flys off.  

This all takes place over the course of maybe 20-25 miles.  So it's extremely fast.  My AC spins very freely.  My alternator pulley is very stable and is in good shape as far as I can tell.  My alternator pulley has a little surface rust but I don't think that's the issue.  Once again, they have a tendancy to flap around like mad.  My PS/WP belt does not exhibit this same behavior.

Does anyone have any idea why this could be happening?  I can't even drive the car more than 30 minutes without having the belts squeal and risk flying off.  Am I alone in this plight?  

Thanks,
Ray

[fspGTD]

I fought v-belt problems on my Rabbit for years, and it progressively got worse.  Changing to a brand new alternator which was a different kind, including replacing the pulley with a brand new one, was revealing: I noticed that the belt no longer needed to be tightened anywhere near as much to get the alternator to "hook up" without squealing, etc.  Also visually inspecting the way the belt sits in the pulley, it sits much nicer in the pulley.  On close visual inspection of the original alternator pulley, I found that it was no longer conical shaped but was compound conical shaped with a convex profile.  This would not allow the belt to sit with full contact as it wold only contact at the edges, and is why it would need ungodly belt tension to make enough "traction" the alternator needs.  This high amount of belt tension and also the deforming the belt does as it goes through the alternator leads to very short V-belt life.  So, I guess the short story is... replace your alternator pulley with a brand new one.

I just bought a replacement pulley kit for dad's '84 Rabbit bosch alternator from the dealer (included both pulley halves, nut, spacer, etc), and I felt that the cost was not unreasonable at about $30.  As I found signs of wear on his pulley and also signs of early belt disintegration on a belt I know I installed myself not that long ago.  A new pulley sure beats breaking belts!

There is potential for the belt to get wound around the crankshaft pulley by the way, burn through the plastic lower timing belt cover, and take out the timing belt.  I've had it happen once to me before, and it ruined a really good head (pistons hit valves, valves bent, camshaft broke into several pieces, piston tops got marred, couldn't have done the bottom end any good, etc.)

[rackley]

Yep, I've been thinking about replacing the pulleys just because I've already replaced the belts who knows how many times in the last month.  However, I was looking at whole alternators, I didn't know the dealer would sell just the pulleys.

Excellent call.

One thing I truely hate about the daisy-chained belt system is that you don't know where the problem is.  Both the AC and Alt belt oscillate like mad at cold idle but once the thing warms up a bit they seem to calm down.  By oscillate I mean you can look at them and even though you tightened them down to only about 3-4mm of play with a stiff finger push, they're bouncing around a good 5mm up and 5mm down from their "normal" path.  The AC belt is even worse, it flaps around like mad.  Now this is obviously a problem with either the belt geometry or one of the belts is transferring force in an impulse fashion...really stiff resistance one microsecond and then really loose the next.  The thing is, who knows which one it is!  

:idea: I could take off the alternator belt and see if the AC belt does it by itself... :idea:  Hmm, once I fix the trans I'll have to do this.  

So I'll do the alternator pulley and alternator tensioner pulley first, if that doesn't work then I'll do the crank pulley as well.

Thanks for the tip  

[chrissev]

my guess would be worn bearings in either the AC compressor or the alternator.  Grab the pulleys and try to move them vertically up and down.  If they move at all, consider that any movement is multiplied exponentially as it is transmitted from the bearing through the pulleys to the belt.  In order to have adjustment capabilities in the alternator bracket, there needs to be no movement in either the alternator or the AC bearings.

[fspGTD]

Just replaced an alternator pulley on an '84 Rabbit Diesel... check it out here: http://www.vwdiesel.net/phpBB/viewtopic.php?t=1306&postdays=0&postorder=asc&start=87

[fatmobile]

The alternator on my A2 was loose.
 The hole near the pully, around the big swivel bolt, was worn to an oval.
 This allowed the alternator to lean in too far.
 I took a piece of 3/8" stainless, about 3/4" to 1" long and ground one side all the way off. I took the half pipe and hammered it around the long alternator bolt.
 I put the bolt into the alternator and tightened it, pressing the stainless half pipe into the alternator hole, where it had worn.
 Tightened it up but it still moves around a little when I move the throttle lever and rev the engine.
 I've done this to most of my A1s too.

[JimK]

I have a 91 Jetta Diesel with a TD transplanted into it.  

I'm having an absolute hell of a time getting the AC and Alternator belts working right.  

I've tried Goodyear, NAPA, OEM, and now even the $15 Gatorback belts.  They all do the same thing - I tighten them down to spec, then they flap around when the car runs (even when tight!  very strange!), then they just stretch out until they're about to flap off.  So then I have to adjust the tension on both, and after about 2-3 adjustments there's no adjustment room left on the alternator pulley.  At this point the belt just keeps getting looser and looser until it squeals and then eventually just flys off.  

This all takes place over the course of maybe 20-25 miles.  So it's extremely fast.  My AC spins very freely.  My alternator pulley is very stable and is in good shape as far as I can tell.  My alternator pulley has a little surface rust but I don't think that's the issue.  Once again, they have a tendancy to flap around like mad.  My PS/WP belt does not exhibit this same behavior.

Does anyone have any idea why this could be happening?  I can't even drive the car more than 30 minutes without having the belts squeal and risk flying off.  Am I alone in this plight?  

Thanks,
Ray

I dont know if this will help, I have a 81 Jetta that gave me a fit and I change out the double shev pulley off a Sandon compressor that came off a BullDozer, the reason was to be rid of the narrow v section pulley on the Alternator and the pulley of the dozer the v sections were the same. I had to replace the pulley on the alternator but I never had a bit of trouble again or slipping belt. I had enough of that narrow belt. Jim

[srivett]

I had a good fight with my brothers '89 yesterday.  It had soo many issues with the belts.   :shock:  The crank pulley was sticking out further than all the others, the alternator pulley was worn out, the alternator was leaning, the car bit me and drew blood, etc.  Anyway, I pulled the alternator and filed down the left hand boss which goes into the IP mount.  This was done for alignment as we didn't have different thickness washers to shim the alternator.  Even so, the alternator pulley was still out 1/2" by the time the belt got to the crank.  I had to loosen the main bolt and pound a big'ole washer between the boss and the mount to straigten that out.  The new pulley was quite a bit deeper so I had to remove the two inboard spacers against the fan.  This prevented me from tightening the bolt down onto the shaft so I had to pound out and reuse the slotted washers from the previous pulley.  After pulling the alternator 5 times we still hadn't gotten the two other accessory pulleys lined up with the alternator and crankshaft.  We were just happy to have made things better than they were before.  

Steve

[rackley]

I'm waiting on my third alternator pulley from 1stvwparts.com because the first two they sent me didn't fit correctly.  The first was for the non-AC car, and the second was for the non-bosch alternator and I have a bosch.  Just a real PITA when it takes them a week to get it and then another week to ship it here.  That's 2 weeks per part x 3 parts, or a month and a half.  For a stinking alternator pulley.  Note to self, go through local dealership next time unless it's a really expensive part with a really steep discount.

[JimK]

I'm waiting on my third alternator pulley from 1stvwparts.com because the first two they sent me didn't fit correctly.  The first was for the non-AC car, and the second was for the non-bosch alternator and I have a bosch.  Just a real PITA when it takes them a week to get it and then another week to ship it here.  That's 2 weeks per part x 3 parts, or a month and a half.  For a stinking alternator pulley.  Note to self, go through local dealership next time unless it's a really expensive part with a really steep discount.

I had to replace my belt a few days ago and it had been on the engine for around 5 years or so. I have found the lawn mower belts are of good quality and dont strech like standard belts. If you could find a belt that would fit like that perhaps that might work for you, good luck, JimK

[rackley]

OK the mystery has been solved.  Apparently the dim-wit that had the car before me put on the WRONG alternator when he got a replacement.  It was from a VW and bolted in and mostly worked, but the pulley was different and didn't protrude the correct amount.

I ordered a junkyard alternator and when I looked at the pulley I could immediately tell it was different from the one currently on the car.  Just for ht heck of it, I took that pulley off, replaced it with the new 2nd pulley I got from 1stvwparts.com and bolted it up and it looks perfectly aligned.  The pulley that's *supposed* to fit my car and my alternator actually fits now.  (fingers crossed that it actually works when I fire the car up this weekend).

[rackley]

Well it appears I spoke too soon.  It's pulling the same junk as the last one did.  New alternator, new pulley, new tensioner pulley.  Still flaps like mad when there's a load (like glow plugs on startup) which stretches the belt and makes it unusable in a matter of minutes.  The AC belt doesn't exhibit any kind of abnormal behavior that I can see.  

Grumble..    :evil:

[92EcoDiesel Jetta]

Well it appears I spoke too soon.  It's pulling the same junk as the last one did.  New alternator, new pulley, new tensioner pulley.  Still flaps like mad when there's a load (like glow plugs on startup) which stretches the belt and makes it unusable in a matter of minutes.  The AC belt doesn't exhibit any kind of abnormal behavior that I can see.  

Grumble..    :evil:

I know rackley's post is 7 years old but I would like to know if there was a resolution to the mystery.

[DogDiesel]

I had this belt system on my previous 1.9AAZ build, it came from MKII.
 Like you, my alternator belt flopped and loosen and I rarely ever go over 20K miles before replacement.

Then I created a counter pulley.

I took a longer bolt on the back of the ALT BRKT under the INJ pump and threaded the shank to match the OEM bolt, then shaved the threads where it came out of the mount.  Then I took a small 2" pulley with bearing that I bought from a lawn mower shop, shaved the outside edges to fit the area without rubbing, put it on thus geting more belt contact with the pulley.

My belts stopped flopping, they lasted.  My voltage came up, obviously the OEM setup had slippage, and with more pulley contact my slippage was nill.

I pulled that engine and put in another AAZ with serpentine.  Love it.  Sweet.  Still have that counter pulley in my shop.

Wayne

[TylerDurden]

...Then I created a counter pulley....

Like this?



I test this setup for a year; in the warm weather it was fine,  but I found in the cold weather, the lugs would rip off the belt, so it is running stock for now.





More puzzling, is the stock system on my '89  works pretty well.