Generator Pulley Nut Loose

Karmann Paul · Posted: Fri May 18, 2007 4:18 am Post subject: Generator Pulley Nut Loose

1967 Beetle. I've had this guy for about 2 months. The first day I had it the fan belt shredded, fortunately I was just down the street from my house and made it home no problem.
1) I got a new belt but it has been loose ever since. After reading other threads I need to verify if it is indeed the right size. At the parts store I asked for a belt for a 67 and took what they gave me
2) New belt is beginning to shred and wear down - because it is loose?
3) The nut doesn't stay tight; I tighten it down, the belt seems to have good tension, the squeaking goes away, but after a few trips around the block it is loose again and the nut is no longer tight. Is there a trick to this or do I need to use a torque wrench on this?
4) There are only 5 shims - right now I have 2 on the inside and 3 outside - Are there supposed to be 10 shims?
I'm trying to get this right before the BugOut in Manassas, VA next weekend. Thanks -Paul

bugninva · Posted: Fri May 18, 2007 5:02 am Post subject:

not sure on the number of shims required, someone else can chime in(or i can count mine) but you need to make *sure* you are getting the pulley nut tight... when you begin to tighten the pulley nut it will become tight on the belt, not the shims...you must let it rotate as you tighten the nut so the belt "walks" up the pulley...once it gets there the pulley will be tightening against the shims...then you secure the pulley and give the nut a good crank to tighten....
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Mr. Loaf · Posted: Fri May 18, 2007 5:14 am Post subject: Shims

The shims on the outside of the pulley are your spares. They were kept there to add to the inside as the belt wore and stretched. You only need 1-2 on the outside. The belt that you need is a 905mm but off hand I do not know the width. If you are shredding belts make sure that your generator and crank pulley are parallel to each other.
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bill may · Posted: Fri May 18, 2007 5:47 am Post subject:

8-10 shims. i run 10. is your generator pully nut a chrome acorn type? the chrome ones bottom out and never get tight.use a stock nut and spacer and if you need chrome then chrome the stock stuff. is your belt a 9.5X900 or 9.5X905 or 10X905???
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Karmann Paul · Posted: Fri May 18, 2007 6:26 am Post subject:

It has the stock nut, not an acorn type. I want to keep the motor as "stock" as possible so it is easier to maintain and follow the directions in the manuals

I will check the size of the belt when I get home tonight. I do remember that it's a goodyear v-belt and has a code number/part number instead of the actual dimensions.

The two pulleys look like they are in line by eye balling them from the side. Anyone know a way to test this? I suppose I could use a level to see if they are even. when I had the belt off the generator tower did not seem loose. Although when I turned the generator without the belt there was a slight squak when first moving or moving really slowly. A little faster and the squeak stops.

I've read a bunch of threads about squaling belts and this seems to be the bane of all "beginner" mechanics. as a beginner I couldn't get through this without the samba - thanks everyone!!

glutamodo · Posted: Fri May 18, 2007 7:51 am Post subject:

squeaking belts are not uncommon, especially ribbed belts.

As Bill said, you NEED to have enough shims in there. 8-10 for sure. He mentioned those awful aftermarket acorn nuts, that's one issue. Another happens though with the stock bell-shaped spacer - if you don't use enough shims, it too can bottom out on the end of the shaft. When that happens, you tighten the nut/bell against the shaft instead of totally pinching the pulley halves and their shims together, this often ends in pulley and/or belt failure.

10x905mm belts are the stock size, (actually, originally it was 9.5x905) but if you have worn pullies (or aluminum ones) , then a smaller belt often works better. I've always ran 900mm belts myself.

pantone149 · Posted: Fri May 18, 2007 1:39 pm Post subject:

Are you holding the generator pully stationary while tightening the bolt? You need to carefully slide a screwdrive into the pully slots and wedge the screwdriver into the generator housing in order to hold the pully in one place. Your problem may be as simple as that.

Karmann Paul · Posted: Mon May 21, 2007 7:18 pm Post subject:

The belt I have is a 900mm. 11AV900 is the code - Good Year belt Seems to be the right size now that I have the nut tightened down correctly - that was the problem - I wasn't tightening it enough. I took a test ride tonight and all seems to be well. One more question - does it matter if the belt is grooved on the inside or the outside? The belt I have on the car is grooved on the inside but the spare I picked up tonight has the grooves on the outside. Is one or the other correct, or better? I think I have everything straightened out and ready for the Bug Out in VA this weekend...thanks everyone!

glutamodo · Posted: Mon May 21, 2007 7:56 pm Post subject:

Where the grooves are doesn't really matter. Personally though, I prefer them with no grooves at all - grooved belts tend to make a whistling noise that makes me think I sucked something in my fan.

johnanddes · Posted: Tue May 29, 2007 2:38 pm Post subject:

KTPhil · Posted: Tue May 29, 2007 3:14 pm Post subject:

8-10 total, apportioned between or outside the pullies depending on how stretched your belt is. Remove (not add) washers to tighten a stretched belt; just store the "extras" under the bell nut.

drscope · Posted: Tue May 29, 2007 3:15 pm Post subject:

VW calls for 10 shims. What goes between the pully depends on your belt. Need to make the belt tighter, remove shims from between the pully halfs. Too tight, add a few.

The spares go outside under the nut and special washer. If you don't have all 10 shims, you may not be getting the nut tight.

glutamodo · Posted: Tue May 29, 2007 3:31 pm Post subject:

KTPhil · Posted: Tue May 29, 2007 3:38 pm Post subject:

I love those photos... they must use that special VW tool, the "anti-grav parts separator tool" I keep checking ebay for...

2067Bug · Samba Member Joined: October 05, 2005 Posts: 600

Has anyone experienced the fan belt tension just right when the engine is cool but getting much too tight after the engine warms up?

Eric&Barb · Posted: Tue May 29, 2007 7:29 pm Post subject:

L572 · Samba Member Joined: April 20, 2002 Posts: 704

..of course we all know that rubber bands contract when heated, but do VW generator and alternator belts do the same? Wink

...and if so, does this compensate for or aggravate Eric & Barb's metal expansion explanation? And since 2067Bug indicated that the belt seems tighter when the engine is warm, that seems to settle it: metal expansion plus rubber contraction equals a tight belt Wink

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2067Bug · Samba Member Joined: October 05, 2005 Posts: 600

Hey guys (Eric & Barb/L572) – I really appreciate the scientific analysis and reasonable conclusion, but from a logical perspective I suspect something else is occurring along with metal expansion. When the engine is cool the fan belt can be set to deflect 1 inch and still gets very tight after the engine warms up. It may be that the chrome pulley system and nut are cheap metal, or the two pulleys (big and small) are not aligned properly. I’m not sure but I will continue to experiment. I welcome all suggestions and comments. Thanks

glutamodo · Posted: Wed May 30, 2007 6:18 pm Post subject:

Chrome pulleys are typically pretty low quality, by the way. I'd go with a steel one myself.

Eric&Barb · Posted: Wed May 30, 2007 6:32 pm Post subject:

Hi 2067Bug,
No problem!! Would be interesting to know what your oil temp is getting up to. Could be it is getting too hot....
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