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Late last season I noticed a chirping sound from the engine when very warmed up in hot outside temps. I thought it might be the alt belt and changed it out late last year in prep for this new season.

Recently on vacation in Florida it got a full test. Again, in hot ambient weather and with the engine well warmed up the chirp sound came to life and even a bit louder than I remembered from late last year. I tried the old belt dressing treatment and it did no good. 

I can't seem to find a good alternator to cooling fan drawing online so my question is please, does anyone had an idea what may be chirping? My thoughts are to remove the fan belt and spin the alt by hand and hope to detect a bad bearing in the alt. Is there another bearing at the back of the alt by the fan housing that may also fail and cause the noise ? Ideas ? Thanks. 

 

David Stroud

 '92 IM Roadster D 2.3 L Air Cooled

Ottawa, Canada

 

Original Post

At back side of the crank pulley, there is a tin that has " tabs" at the 3 and 9 o'clock positions. In the warmer ambient air temps the tin or crank pulley may be expanding few thousands and just enough for the tin to touch the back side of the pulley. The fix is  to wiggle a screw driver between the two surfaces creating gap. If that doesn't resolve the issue then you are on track to remove the belt to locate the source which may be the fan lightly touching the shroud that involves a light shale and twist of the fan shroud and that may resolve it , but the correct way is to add or delete one or more of the round fan shim washers which I don't think you want to get involved with while you are in Fl.

Last edited by Alan Merklin
Alan Merklin posted:

At back side of the crank pulley, there is a tin that has " tabs" at the 3 and 9 o'clock positions. In the warmer ambient air temps the tin or crank pulley may be expanding few thousands and just enough for the tin to touch the back side of the pulley. The fix is  to wiggle a screw driver between the two surfaces creating gap. If that doesn't resolve the issue then you are on track to remove the belt to locate the source which may be the fan lightly touching the shroud that involves a light shale and twist of the fan shroud and that may resolve it , but the correct way is to add or delete one or more of the round fan shim washers which I don't think you want to get involved with while you are in Fl.

Thanks, Alan. We just got home tonight and I'm looking to get this fixed in prep for Carlisle. I'll give it a look on the weekend. BTW, we stayed one night at the Courtyard in Shippensburg on the way down. Nice as always. 

Trailering the Roadster on the trip was uneventful and convenient but way less fun than driving. 

Last edited by David Stroud IM Roadster D

Years back, I was hearing a chirping sound after I did a tune up. I thought it was maybe  the generator going out so I flip the belt off and it still had the noise. I mess around with this for days trying to find the source of the sound. I asked my friend at a Porsche repair shop if he had any ideas what it might be causing the sound. He said to make sure the rub block in the distributer was greased or it would get hot and chirp. Sure enough, I forgot to lube the cam block for the points. A dab of Bosch grease on the block and the chirp was gone.

Butcher Boy posted:

Years back, I was hearing a chirping sound after I did a tune up. I thought it was maybe  the generator going out so I flip the belt off and it still had the noise. I mess around with this for days trying to find the source of the sound. I asked my friend at a Porsche repair shop if he had any ideas what it might be causing the sound. He said to make sure the rub block in the distributer was greased or it would get hot and chirp. Sure enough, I forgot to lube the cam block for the points. A dab of Bosch grease on the block and the chirp was gone.

Thanks for that but I have no points and the chrip is much louder than a points cam could be. 

David Stroud IM Roadster D posted:
Alan Merklin posted:

At back side of the crank pulley, there is a tin that has " tabs" at the 3 and 9 o'clock positions. In the warmer ambient air temps the tin or crank pulley may be expanding few thousands and just enough for the tin to touch the back side of the pulley. The fix is  to wiggle a screw driver between the two surfaces creating gap. If that doesn't resolve the issue then you are on track to remove the belt to locate the source which may be the fan lightly touching the shroud that involves a light shale and twist of the fan shroud and that may resolve it , but the correct way is to add or delete one or more of the round fan shim washers which I don't think you want to get involved with while you are in Fl.

 

Alan, I took a look behind the crank pulley and there's no sign of any scraping against any tin. Further research shows that there may be a chance that the cooling fan may be rubbing against the cooling housing and my test there will be to drive the car in hot conditions till the chirping starts, stop the engine, remove the fan belt as quickly as possible and turn the alt / fan by hand listening for any scraping. I probably should check that big nut at the back first to see if it has loosened in any way allowing a minor wobble. 

If I do find chirping by turning by hand, info shows that the fan can be shimmed back a bit which looks like a simple but tedious task. Any idea where to get such a shim ? Would they be a common hardware store item or a dedicated VW part? 

Again, there is no chirping when the engine runs on startup. Just very pronounced when the engine is completely warmed up in warm to hot ambient temps. Thanks. 

 

Last edited by David Stroud IM Roadster D
David Stroud IM Roadster D posted

If I do find chirping by turning by hand, info shows that the fan can be shimmed back a bit which looks like a simple but tedious task. Any idea where to get such a shim ? Would they be a common hardware store item or a dedicated VW part?

David, I picked up a couple of these Gene Berg fan spacers when I ordered my new fan.  http://www.geneberg.com/produc....php?products_id=808

mppickett posted:
David Stroud IM Roadster D posted

If I do find chirping by turning by hand, info shows that the fan can be shimmed back a bit which looks like a simple but tedious task. Any idea where to get such a shim ? Would they be a common hardware store item or a dedicated VW part?

David, I picked up a couple of these Gene Berg fan spacers when I ordered my new fan.  http://www.geneberg.com/produc....php?products_id=808

That helps with pulley alignment but I don't think it's going to help David's problem.

mppickett posted:

I agree Al,  the Berg ones are more for the alt pulley. But, seems like the last time I looked at the diagram, there were a few spacers inside that allowed a small amount of front to back adjustment on the fan. 

 

Aren't they more like the shims that go under the gen/alt. pulley nut? And they go under the big nut at the fan end?

Last edited by ALB

@Michael Pickett wrote- "The only thing I found in my old one was a 2mm slotted wavey spacer right behind the 36mm nut. "

I have heard of people having to space the fan away from the gen/alt side of the fan shroud- usually just 1 or 2 shims so it doesn't rub. Could you check for me if the big pulley shims will fit over the hub? I don't think I have 1 handy to take apart to check. Thanks in advance! Al

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.

ALB posted:

@Michael Pickett wrote- "The only thing I found in my old one was a 2mm slotted wavey spacer right behind the 36mm nut. "

I have heard of people having to space the fan away from the gen/alt side of the fan shroud- usually just 1 or 2 shims so it doesn't rub. Could you check for me if the big pulley shims will fit over the hub? I don't think I have 1 handy to take apart to check. Thanks in advance! Al

Yes,. Pulley shims fit (tightly) over the hub.IMG_20200311_094843

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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.

the problem is using replacement parts that are not built like the OEM parts. either the rear half of the pulley is loose on the hub or the front half is loose on the hub. either one will cause the same noise. I have tried several new ones available from PPI, IMC, wolfsburg and so on. the best is using a CB billet stock pulley.

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.

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.

Mike

 

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. 

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Big hat's off to Anthony today for some very quick help. My new CB Performance alternator pulley finally arrived to day via USPS and Canada Post. The new pulley parts are just beautiful but I noticed from the get go that this CB pulley has a larger diameter than the pulley that was on there. My problem was that I needed advice on where / how to source a new belt of the correct length. It turns out that the existing belt is 840 mm and the replacement belt needs to be about 912 mm. Anthony made it easy and the local Napa will have one for me tomorrow at 8 am.  Thanks, Anthony...nice one !!

mppickett posted:

Hi David, I'm glad it's coming together. Just curious, do you have a power crank pulley or a regular size one?

Mike

Giday, Mike. I don't know much about my engine other than it was built 55,000 km ago by a fellow in Vancouver, Canada that had a good reputation. Here's a pic of the new CB Performance alt pulley just sitting on the shaft and my hand holding one half of the pulley that had gone bad. Full o.d of the new ( black pulley ) is 4 1/4" and the one I'm holding is 3 3/4"o.d. 

I don't know what a crank "power" pulley is, nor do I know the o.d. of a regular sized one. My crank pulley is shown in the second blurry pic. It is 5 3/4" o.d. 

Now  quick poll to help make a colour decision on a small plane I'm rebuilding. 5th pic is the type of plane....just a small single seat job but it needs to get painted in Military yellow or silver. Which colour do any of you like, please ? Yellow 3rd pic or silver 4th pic ? Thanks. 

 

 

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David Stroud IM Roadster D posted:
Giday, Mike. I don't know much about my engine other than it was built 55,000 km ago by a fellow in Vancouver, Canada that had a good reputation. Here's a pic of the new CB Performance alt pulley just sitting on the shaft and my hand holding one half of the pulley that had gone bad. Full o.d of the new ( black pulley ) is 4 1/4" and the one I'm holding is 3 3/4"o.d. 

I don't know what a crank "power" pulley is, nor do I know the o.d. of a regular sized one. My crank pulley is shown in the second blurry pic. It is 5 3/4" o.d. 

Now  quick poll to help make a colour decision on a small plane I'm rebuilding. 5th pic is the type of plane....just a small single seat job but it needs to get painted in Military yellow or silver. Which colour do any of you like, please ? Yellow 3rd pic or silver 4th pic ? Thanks. 

 

 

Hi David, The normal size of the alternator pulley is 4 1/4" so your bad one may have been an undersized pulley. Your crank pulley is a "power pulley." Normal size crank pulleys are around 6 3/4" and folks often switch to a smaller pulley to reduce the speed of the alt/fan to save power at high rpms.

Regarding paint color, I like the look of the silver with yellow trim (4th pic). The silver helps to set off the shape of the cockpit. Very nice looking plane!

Thanks,

Mike

Stan Galat posted:
David Stroud IM Roadster D posted:

Giday, Mike. I don't know much about my engine other than it was built 55,000 km ago by a fellow in Vancouver, Canada that had a good reputation.

 I believe Darren Krewenchuck built the engine for Ron Leonard.

Correct. And it sure would be nice to see what's inside....but no I won't until necessary.

David, your old pulley ratio is 1.53:1, you new one is 1.35:1. The new ratio with your larger pulley is 13% SLOWER than before. You might want to keep an eye on your head temps.

Stock fan ratio is 1.59:1, the stock fan is the fastest and flows the most air. Your new ratio is almost 18% slower than stock. I'd pay attention to oil temps. And buy a CHT gauge.

Or, the best solution? Buy a stock size(6.75") degree pulley and another even longer belt. Take the crank pulley off first to see if it's the stock threaded type or sand seal.

Last edited by DannyP
DannyP posted:

David, your old pulley ratio is 1.53:1, you new one is 1.35:1. The new ratio with your larger pulley is 13% SLOWER than before. You might want to keep an eye on your head temps.

Stock fan ratio is 1.59:1, the stock fan is the fastest and flows the most air. Your new ratio is almost 18% slower than stock. I'd pay attention to oil temps. And buy a CHT gauge.

Or, the best solution? Buy a stock size(6.75") degree pulley and another even longer belt. Take the crank pulley off first to see if it's the stock threaded type or sand seal.

I'll look at the crank pulley situation tomorrow. What are the implications of stock threaded type or sand seal ? 

I checked with CB Performance today because they sell two non stock pulleys. PN 1931 which is what I bought for about $75 and PN 1912 for about $45 and this one looks to be a smaller diameter on the website. In fact they are the same diameter at 4.25 ", just that the last one is made in Taiwan and the better one is made by CB Performance. 

So now I'm wondering why would they make one that would turn the cooling fan slower than stock ? 

David Stroud IM Roadster D posted:

I checked with CB Performance today because they sell two non stock pulleys. PN 1931 which is what I bought for about $75 and PN 1912 for about $45 and this one looks to be a smaller diameter on the website. In fact they are the same diameter at 4.25 ", just that the last one is made in Taiwan and the better one is made by CB Performance. 

So now I'm wondering why would they make one that would turn the cooling fan slower than stock ? 

My understanding  is that it’s the other way around. There is the stock diameter VW generator/alternator pulley and then they started using the Porsche 356 diameter pulley which is smaller to get the fan to turn faster.

Think of this like a multi-speed bicycle. A bigger ring up front and a smaller gear out back means you go faster, but it takes more power to push the gear.

The crank pulley is like the big ring on the bike. A smaller pulley means the fan turns more slowly. A larger pulley means it turns faster.

The fan/alternator pulley is like the gears in the cassette on the bicycle's rear wheel. A smaller pulley means the fan spins faster, a bigger one means it turns more slowly.

The only way to overdrive the VW fan is to put a stock diameter pulley on the crank, and the smaller 356 fan pulley on the alternator. I wouldn't do this without a welded and balanced fan. Even then, I wouldn't spin my engine over 6500 RPM or so.

Most people want no more fan speed than they absolutely need. Spinning the fan more slowly means there is more power available for motive power. That's why this arrangement is called a "power pulley". There are many different combinations to play with. 

Last edited by Stan Galat

Good Morning to some and Good Afternoon to others.

this pulley thing is simple...stock gen/alternator is 4 1/4" OD,  but found some early pulleys measured 4 3/16" OD

CB performance billet pulley measures 4 1/4" OD

356 porsche is 3 3/4" OD.

stock steel crank pulley [with grooves and no seal] measures 6 7/8" OD

JC measures 7" OD with or without grooves for a seal.

Scat alum pulley measures 6 3/4" OD either with grooves or without for seal.

aftermarket "power pulleys" measure 5 1/4" and were designed to clear dry sump pumps and slow the fan speed and resistance at higher rpm's.

The popular trick of the days past was to use the 356 pulley to speed up the fan speed at lower rpm's. of course it also increased fan speed overall but the negative point was the fans would come apart.

Overall I have ran all these combo's and they were suited for each situation. there's not one correct application unless it's 100% stock. Same logic goes for the seal no seal topic. what ever works for your application. several people feel they need a seal at the front pulley to eliminate oil leaks. Most cases your oil leaks are due to TOO Much Crankcase pressure.

Hope everyone is doing well with all the things going on. no better time to work on that classic.......just think of it as a job and when you walk out to garage for 8 hours you won't hear your other half ask " what are you doing" every 10 minutes

Stan Galat posted:

Think of this like a multi-speed bicycle. A bigger ring up front and a smaller gear out back means you go faster, but it takes more power to push the gear.

The crank pulley is like the big ring on the bike. A smaller pulley means the fan turns more slowly. A larger pulley means it turns faster.

The fan/alternator pulley is like the gears in the cassette on the bicycle's rear wheel. A smaller pulley means the fan spins faster, a bigger one means it turns more slowly.

The only way to overdrive the VW fan is to put a stock diameter pulley on the crank, and the smaller 356 fan pulley on the alternator. I wouldn't do this without a welded and balanced fan. Even then, I wouldn't spin my engine over 6500 RPM or so.

Most people want no more fan speed than they absolutely need. Spinning the fan more slowly means there is more power available for motive power. That's why this arrangement is called a "power pulley". There are many different combinations to play with. 

Absolutely; I later switched to a welded and balanced fan with my 356 pulley. VS shipped them with the 356 pulleys but with regular stock fans.

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