hepkat63

Hi all,
well, if there is something I know - it is nothing is as easy as it should be.

I think my alternator pulleys need replacing. Here is why.

A few months ago when I took out my alternator and replaced (and painted) my fan along with the fan bearing - I replaced both belts as well - fan and alternator as a precautionary measure.

All has been going fine. However, i did notice that when I put on the air conditioner over summer, I would occasionally hear a squeal from the rear and smelt burning rubber - so I turned off the air conditioner and never really needed it again (end of summer).

On the weekend, I decided to check the belt tension. I had about 3/4 inch play, which I though too much - even though it was running fine and never smoking at all (until a/c on). When i pulled the pulleys apart - i had one shim in there (thin) - so I removed that so now there were no shims. Re-assembled and started it up. Bloody smoke everywhere !! So - quickly turned it off again.

Now, I had replaced the belt correctly - rotating the engine as I went and yes, it was the correct 760 belt too.

Doubting myself, i rang our porsche dealership and spoke to the mechanics there - and they confirmed i was correct in my procedure.

I decided to start again - and used a brand new 760 belt (i have 3.6 litre and tiptronic and all the PET say this is correct). Put TWO shims between the pulley halves - and rotating the motor as I went - tighted it all up. Book says 37 foot pounds.

Started the car and let run for about ten seconds. The belt was too hot to touch and just starting to smoke. So, i removed one shim - tried again - same thing. Removed ALL the shims - same thing.

I still have about 1/2 play in the belt - so the only thing I can think of is perhaps the pulley insides are worn enough so that the belt will not sit high enough.

Am I dumb ? Does this sound feasible?

robt964

If there is no perceivable groove or evidence of wear on the inside of the pulley faces, I doubt they'd need replacing. Does everything spin freely with the belt off? I guess the pulley halves could have become deformed but it seems unlikely. Is the belt running square? ie the position of the alt pulley is exactly inline with the coresponding crank pulley? If this is not the case the belt will rub up against one of the pulley halves and generate a lot of heat quickly. Check you have assembled the pieces between the alt fan and the pulley in the correct order and orientation (see PET or tech manual). A belt that has overheated is likely to have worn very quickly and increased the slack.

alexjc4

We recently had a similar issue burning belts due to refitting the offset spacers incorrectly on Frank's car, so I would definitely check that - basically the top pulley ends up out of line with the bottom pulley.

owners manual and PET are good for showing where the shims go but this image below is slightly clearer than the owners manual and PET when it comes to the orientation of the spacers, basically the bigger diameter side is against the alternator pulley halves: (ignore the big red arrows, I stole the image from a thread on a different topic on pelican)

BTW my book says 9.5mmx763mm for a Tip alternator belt.

hepkat63

yes, there is a bit of wear there - certainly not new looking. I am thinking that given a tiny shim makes the belt tighter or looser, just some of the equivalent wear on the pulley(s) would be enough to cause this.

hepkat63

thanks for that - yes, i considered this too and to the naked eye, it looks aligned. All I have between the front pulley half and the fan pulley assembly is the one thick cone washer with the cone facing the front of the car (as per the PET).

The only thing that I have done differently this time is torqued the nut to 37 pounds (as per book). Last time I did it (a few months ago) I did not have an opened ended torque wrench, so just did it up as tight as I could.

GazC2

So you now have no shims in either of the pulley`s ?

hepkat63

right now the pulleys are off until I work out a way forward.

GazC2

I think I had three shims in the back pulley and one in the front I have a note in the garage when I put it all back together recently, like the previous comments I would be surprised if the pulley halves are the problem

HalV

Do you have this (Green Arrow) cone washer facing the correct way?

HalV

Also, what did you do with the shims that are not being used (between the pulley halves)?

Jacke2c

I thnk your bearing is going bad and trying to turn both belts at the same RPM.... this would heat the belts..... Just a thought.

PelicanParts.com

Always have some DIY Tech Articles that could be helpful on our site as well.

hepkat63

thanks guys for the help - as always, much appreciated.
@GazC2, thanks that would be useful
@HalV, Yes, the cone washer round part is facing front of car (alternator), and the other shims are at the back, I started with nut, cone washer, one thin shim, pulley half, two thin shims, pulley half, cone washer (facing other way).
@turbotwoshoes, the bearing is (was three months ago) brand new, and if I don't use the hex tool, the shaft spins, so I don't think it is the bearing.
Will have another look tonight after work.

GazC2

So I refitted as follows

Nut
Cone washer
1 shim
pulley halv
3 shims
pulley halv
cone washer

I cant find the note for the back pulley shims

JB 911

+1 it has this written all over the symptoms. To my knowledge you can not see this washer to check without removing the alt pulley half. The outer one, yes, but not that inner one.

There was also an updated pulley half from Porsche that builds this washer into the alt pulley to remove the opportunity to install it backwards. I believe they came out with this because so many techs put it in backwards, started it up got smoke squealing and and then figured out what they did.

Could be something else, but I'd take off the pulley and lay your eyes on it again before I dug deeper.

Good luck.