Alternator pulley

[mike202]

Been on a run out today about 60 miles or so. I thought the engine sounded a bit noisy so when I got home had a look and found the belt was loose, although hadn’t noticed the light come on so it wasn’t that loose. Removed the pulley wheel to investigate and I found that the inside half was cracked nearly all the way around the centre.
It’s been on for about seven years since the conversion from the old generator. Not sure why this has happened but I hope it’s a one off.

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[sparkywig]

That cracking can be caused by the alternator not mounted correctly, an eccentric alternator bearing and/or overtightening the fan belt.
Have you checked the alternator is sitting directly in line with the crank pulley and that the shaft rotates without a wobble?

 

[mike202]

I’m pretty sure the alternator is in line with crank pulley. I checked for play before I removed the top pulley and it seemed ok. Bit of a mystery really, I keep the fan belt at the right tension in fact I recently removed a shim to tighten it to about 10-12mm.
Are the billet aluminium pulleys any good?


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[mike202]

That cracking can be caused by the alternator not mounted correctly, an eccentric alternator bearing and/or overtightening the fan belt.
Have you checked the alternator is sitting directly in line with the crank pulley and that the shaft rotates without a wobble?

Double checked the alternator shaft for any wear and no wobble, woodruff key looks fine. Thanks for the advice.


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[mike202]

Luckily I found my old pulley wheel in my parts stash. Cleaned it up a bit and it fits fine. I did notice that the belt is tighter in this pulley so I needed 8 shims between the two halves.

I was going to just replace the broken inner half and keep the newer on the front. In the end I thought the two matching halves would be best especially as they match up with the two tongues in the wheel.

Runs fine and sounds ok.

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[Dirty Harry]

Hi Mike, that pully with the tabs is a og VW pully and these are perfect, i have the same they even balanced these!

 

[mike202]

Thanks Harry, that’s good to know. Saves me buying a new one. [emoji106]


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[mike202]

Update on new pulley-

After doing a few test drives and all seemed well, I decided to take the bus on a longer trip of about 100 miles. Checked the fan belt several times, all fine, then when home I went to the garage and found the fan belt and pulley nut loose [emoji57]
I inspected the two halves of the pulley and there is no sign of any damage to them fortunately, although the forward half against the alternator is dusty. It went on clean.
I’ve checked the tightness of the alternator strap and fan hub nut so the only thing I can think of is that the alternator bearings are wearing out after about 28k miles. (May 2014)
Time for a new one maybe? Any ideas anyone, or comments all welcomed.


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[Dirty Harry]

Mmmm.. it’s important to have a couple of shims between the 2 halves, the 2 halves need to rest against the shims!

 

[mike202]

Mmmm.. it’s important to have a couple of shims between the 2 halves, the 2 halves need to rest against the shims!

I had 8 shims between the two pulley halves. I didn’t have any on the outside though just the domed washer and nut.


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[Dirty Harry]

Ok, what i do is thighten the pully nut after a few turns so the v-belt creeps higher and the front halve sits nice and straight before thightning the nut

 

[sparkywig]

Mmmm.. it’s important to have a couple of shims between the 2 halves, the 2 halves need to rest against the shims!

I had 8 shims between the two pulley halves. I didn’t have any on the outside though just the domed washer and nut.


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You should have 10 shims, and all must be used whether between the pulley halves or under the nut and washer.
Cracking around the centre of the pulley is caused by the belt being too tight.

 

[mike202]

Ok, what i do is thighten the pully nut after a few turns so the v-belt creeps higher and the front halve sits nice and straight before thightning the nut

Thanks DH, everything has been fine until just recently not sure what I’ve done to cause this if anything!


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[mike202]

Mmmm.. it’s important to have a couple of shims between the 2 halves, the 2 halves need to rest against the shims!

I had 8 shims between the two pulley halves. I didn’t have any on the outside though just the domed washer and nut.


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You should have 10 shims, and all must be used whether between the pulley halves or under the nut and washer.
Cracking around the centre of the pulley is caused by the belt being too tight.

I’ll have to get a couple more. Interesting that in Bentley there are only 7 shims in the picture. (Lubrication and maintenance fig 5.4). I’m not doubting your right though, as I’ve read elsewhere that 10 is the right number of shims.
When I put the OG pulley wheel on which hasn’t cracked, I make sure there is always 10-12 mm deflection of the belt. So I don’t understand why the pulley nut has come loose this time.


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[ozziedog]

Possibly, you may have just had a rubbish belt, I don’t know of any particular problems with any, however it does seem remarkably noticeable that anything with rubber in it in the last few years does appear to be somewhere between crap and diabolical.

Ozziedog,,,,,,,,,just a thought :mrgreen:

 

[mike202]

Thanks Ozzie I’ll try a new belt.

Is it possible that the alternator bearings are on the way out even if I can’t hear or feel anything wrong with it? Or is it usually obvious that the bearings are wearing by grinding noises or a slight movement of the alt shaft ?


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[sparkywig]

If the alternator bearings are wearing there would be play fore and aft, and the shaft may rotate out of true.
When you next take the belt off give the pulley a pull back and forward and maybe set a dial gauge up to check the rotation.

 

[mike202]

Thanks. I haven’t got a gauge but seen them on Amazon and may buy one.

For now I’ve decided not to buy a new alternator. I’ve bolted everything back up and put another spare belt on. I’ve added two more shims so that’s ten altogether. This belt has five shims between the halves, and five on the outside under the dome washer.
There’s no sign of any noise or movement of the alt shaft, ( without a belt on) and it’s putting out 14.25V when I increase the revs a bit.

I’ll give it a test drive over the next few days and keep my fingers crossed [emoji1696]


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[davidoft]

Thanks. I haven’t got a gauge but seen them on Amazon and may buy one.

For now I’ve decided not to buy a new alternator. I’ve bolted everything back up and put another spare belt on. I’ve added two more shims so that’s ten altogether. This belt has five shims between the halves, and five on the outside under the dome washer.
There’s no sign of any noise or movement of the alt shaft, ( without a belt on) and it’s putting out 14.25V when I increase the revs a bit.

I’ll give it a test drive over the next few days and keep my fingers crossed [emoji1696]


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there were quite a few poor quality repro pulleys that failed like that, the usual fix was to fit a genuine used one, if you can't feel and rumble or noise in the bearing then they are fine, you keep an out on it for a while but im pretty confident its the poop quality pulley

 

[mike202]

Thaks for the comments, appreciated.