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DannyP posted:

David, sometimes a spacer on the back side where the fan resides moves the fan out just enough to stop any metal to metal contact between the fan and the shroud. There should only be spacers on the pulley side to line the two pulleys up perfectly. At least that's my opinion.

Thanks Danny. That is my understanding too. I'll get into this very soon. Just playing catch up now after a longish holiday. 

Not a lot of experience here, but the aftermarket pulleys are not as strong as the original VW and Porsche versions and they tend to flex a lot with the force exerted by the fan belt.  If the pulley shaft hole is not tight enough to the shaft, it allows the center hole to wear to the point where the halves wobble - always wider at the top and narrower at the bottom and as it wobbles, it wears the center hole more and more.  That movement is probably what you’re hearing.  Doubtful that you can duplicate the sound by hand with the belt off.

Last edited by Gordon Nichols
David Stroud IM Roadster D posted:
Anthony posted:

your chirp is your alternator pulley. the pulley's half against the alternator is moving. replace it with a CB billet one and your noise goes away. a little white grease on the belt also helps

Thanks for that, Anthony. You seem pretty certain. If the front ( fan belt side ) pulley nut is on as tight as it should be, are you saying the back half of the pulley is " wobbling" causing the chirp noise with the belt or are you suggesting it is loose or what, please ? 

Further, how much deflection should be in the belt when all is warmed up ? Thanks.

David, regarding your question about how tight the alternator belt should be when warmed up, I can tell you from my research on exploding fans that general wisdom is that a little bit loose is much better than too tight. The John Muir bible says to shoot for 1/2" to 3/4" deflection in the belt.



mppickett posted:
...a little bit loose is much better than too tight. The John Muir bible says to shoot for 1/2" to 3/4" deflection in the belt.


Mine's at 1/2", and @Anthony was the last one to set it.

A little loose is better than tight because too tight over stresses the alternator bearings.

(Hmmm... maybe too tight over stresses the pulley, too?)

If the belt is too loose, I think you will see it visibly flopping around as the engine idles.


Gordon Nichols posted:

Hey, now that I think of it, I had a dune buggy once that had a similar chirp and on close inspection I found that the fan pulley itself had begun to fracture and was letting the belt slip.  Not saying that this is your problem, but please check for cracks around the center hub, okay?

Yup thanks and gotcha but are you talking about the inner or outer ( rearmost ) half of the pulley ? I'm thinking inner ...please confirm. This thread if left alone could be valuable for future reference. 

David Stroud IM Roadster D posted:
Gordon Nichols posted:

I totally agree with Anthony.  Back when VW ran generators, the bearing closest to the fan pulley would dry out and chirp under acceleration.  It was pretty common.  Install a new bearing and it was cured for a few years.  Rinse and repeat.
I have not seen the same thing with the newer alternators (better/bigger sealed bearings?) and totally believe that the back half of the pulley is at fault.  Try the rear spacer trick behind the pulley.  It’s cheap and easy to do.  It’s just a flat washer.

Ok...I haven't had time to get the front pulley apart and Anthony did not answer my question about the possibility of pulley wobble, so Gordon, I'll ask you. What is at fault with the back half of the pulley ? Crooked and wobbles causing belt / pulley chirp ? What would adding a spacer behind the pulley achieve ? Thanks.

the problem with the pulleys is old stock ones get worn and begin to have play on the hub or the portion the outer pulley slides over. the hub will have a groove or wear marks on it. if that's fine then the outer portion may be loose or worn where it contacts the hub. we done enough of these I don't bother looking for a good old stock one that we just use the billet cb one. it comes polished, chrome, and black. [sounds like an ad].

other noises the pulleys contribute to is one thinks the fan is rubbing and it's the pulley. or the fan is loose on the hub.

I apologize for the late response, work called.

Thanks for the help, Lads. Got the pulley apart today and was very surprised to see the condition of the pulley halves. Galled, grooved and traces of a thin, rubber rubber ring around the lower inner edges of the halves from the belt. The halves were fairly loose fitting on the hub as predicted by some. Nicely, the alt shaft rotated smoothly with no evidence of the fan rubbing on it's housing inside

CB is not open today but the new pulley will get ordered on Monday. Happy to see an easy fix. 

One nice pic of the Bride on the Flagler Loop a couple of weeks ago. We enjoyed the trip so much we bought a house down there. Second pic. Joke only, that house may have been owned by Rockefeller or one of his buddies down on Jeckyl Island, Ga where we hung out for two nights on the trip. 


Images (3)
  • Alt pulley inner half
  • Jeckyl Island
  • IMG_0543

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