Last week the fan belt on my 74 2.0 snapped. the belt was old, frayed and dried out. Luckily I had two new belts in my stash of spare parts. I installed a new belt (Semperit 9.5 X 965). After 5 to 10 minutes of running the belt popped off. Reinstalled the belt with the same result. Tried 3/4 more times with same result. Tried to install the second new belt with the exact same result. Belt was tensioned each install. Now, after about 10 tries I am completely frustrated with what I thought would be an easy maintenance fix. What is going on and what am I doing wrong?

Bob Soldani
74, 2.0

Probably a condition where the alternator pulley and impeller ring are out of alignment. Check the alignment of the alternator ... if it's cocked the belt will come off.

Secondly, check the alternator pulley for cracks.

Third, make sure your impeller (fan) is not loose.

I've seen the pulley installed backwards more than a few times. The long 'nose' at the center should be out (on the nut side).

right size belt?

Been there, done that ..

/Lars S

Are you tightening the second bolt on the Alt when tensioning the belt?

The one that you can access through the oval hole is the upper.
If the lower bolt is really loose, the alternator could still flop around with the engine running.

Actually, the easy test to see if your pulley is on backwards is to reach down in there and if you can fit fingers between the alternator and the pulley, it's backwards. The correct way there is almost no room between the pulley and alternator body.

Thanks to all for your suggestions and possible solutions. I do have the correct sized belt for the car 9.5 X 965. I have tensioned everything and the belt is tight. Never had a problem in a few thousand miles of driving prior to the belt breaking. I can feel the alternator pulley slots around the circumference of the pulley and they are on the inside, closest to the alternator body. Checked a friend's alternator and the pulley slots are on the outside of the pulley, away from the alternator. Seeing as I didn't have a problem before with the belt popping off and not doing anything to the car, why would the belt stay on before and not now? I can put my fingers behind the pulley all the way to the shaft. Pulley seems tight and there is about 3/8" (estimated) of threads from the pulley nut. $64,000 question: How can I remove the pulley while the alternator is in the car. Is it possible? Are there any tricks?

Thanks
Bob Soldani

The new belt could have another grip and tension thats why it climbed off.
You can flip the pulley with the alt in the car...Ive done it once it is wery narrow and tight.... normally the pulley just comes off without any force. The critical moment is to take care of the wodruff key and make sure it stays in place when sliding the pulley on again.
Its WERY easy that the woodruff slides out if its groove when you slide the pulley on which is hard to notice! Possibly it could be glued in the groove first.
Use a mirror if neccesary and some light and take it easy and you will be fine.

/Lars S

if you do pull the alternator for service, I would suggest a new wire harness from Jeff Bowlsley. He is a member here and makes them.

The problem is that the pulley is backwards. Why would it matter if it worked before? It doesn't work now and now you know why. Put it together right and your problem will be fixed. I can make the swap in about 45m with the car on ramps. It's really not a huge job.

A large screwdriver in one of the slots that you can feel will hold the pulley while you loosen the nut.

Thanks again everyone. I will try to remove the pulley and install it correctly.

Well today I finally removed the alternator pulley and reinstalled it correctly without removing the alternator from the car. Fan belt was installed and tensioned. Lo and behold the fan belt now stays on! Drove the car for about 20 miles at various speeds (city and highway) and the fan belt stayed on. Problem solved. Thanks to all for your suggestions. You hit the nail on the head!

Bob Soldani

Good to see you got it worked out Bob.

I hope to see you around.

John

The thing that causes this is it looks wrong when installed correctly and it looks right when installed wrong. At least IMHO. That one caught me too on an alternator rebuild.