throwing fan belt

[joetiii]

I'm wondering if anyone has a problem throwing there fan belts.

On the way to work this AM, I took a 90 degree turn onto a country going and nailed the gas. Car responded well with no oversteer or tire slip. I looked on my dash and noticed the alternator light was on so pulled over. Looked under the lid and saw the belt was thrown. Now I replaced the belt 800 miles ago and when I was checking the oil the other day, the belt was snug on the pulley. The belt appeared a little chafed but certainly not totally worn from slipping. Fortunately, I had another belt on hand and was able to get the new one on in shot order. Anybody have a similar issue of throwing belts on sharp corners under accel?

BTW, I have been autocrossing the car so its no like I was hammering it just this once.

[GH85Carrera]

It is a good thing you watch the alternator light.

My 911 has never thrown a belt. My belts are never more than 4 years old. I turned 132,000 miles on the way to work today.

[kodioneill]

check for pitting/rust on crank pulley doesn't take much.

[tcar]

Throwing THEIR belt?

Is it too tight? That can do it.

I've never had a belt fly off.

[janz]

Joe check your fan/alt pulley for any play. If thats Ok take a straight edge (metal preferably) and lay it against the crank pulley and see how it aligns to the fan/alt pulley. If alignment is good and no play found in either you my have just a bad belt.
Never threw one myself but I change it every year. Miss our spirited Sunday rides, Bill is stricken with lukemia and has not been able to go out.

[mpetry]

Former 912'er so some experience with belt problems. Good buddy back east, very meticulous with a gorgeous 68 soft window targa, had a couple years of belt problems. If you are throwing the belt, something is moving! You should of course make sure the crank pulley is properly torqued, but I'd be looking at your alternator pulley. Is there any chance it was'nt tight ? Remember you have to get all the shims lined up to properly seat them on the shaft, and of course set the tension correctly by swapping the shims from "inside" to "outside".

In my opinion the biggest problem is that you don't have the full compliment of shims and so the nut is bottoming out. This means that the outer pulley half will wobble. It may even "feel" like it tightend down securely. Check to make sure you have the full complement of 6 shims, and remember that more shims between the pulley halves is "looser", less shims is "tighter".

There was one other problem I remember, somebody years ago had their pulley halves powder coated - bad idea - the belt melted in about 20 miles. The pulley should be smooth and cad-plated on the outside, shiney bare metal on the inside. Check for roughness or abrasion on the portion where the belt rides.

Mark Petry
Bainbridge Island, WA
81 SC

[GBStu]

I threw mine at a recent DE.......it was too tight. Stu

[joetiii]

thanx... i will check for overtightness and play on both the crank and alternator pulley.

Jan... sorry to hear about Bill. Summer is always busy with family. I'm lucky to have made one autox per month. Anyway, we shpould get out one more sunday before the snow flies.