fan belts

Yesterday I was driving through town and lost a fan belt. The rubber portion separated from the fabric. I went to the parts store a got an exact duplicate of the factory belt. That belt blew in five miles. Both belts seemed rather tight to me. Is there a spec on the amount of tension on a fan belt? I finally bought one that was one inch longer and used all the pulley spacers. Anybody have any ideas about this. This is Phoenix and it's 100 degrees!!Help

Gary:

Go get a Gates 7355 toothed belt (accept no substitutes!!) and then check the knowlege section of this site for proper tightening process. You shouldn't be chewing them up that fast - make sure the alternator pulley is in line with the crankshaft pulley by sighting along both of them from the side or the top to make sure they're in line with each other. Also, just for the heck of it, make sure the alternator/fan assembly is turning easily and smoothly with little resistance, and that both pulleys are not bent or wobbling and running true.

gn

In all VW models,the fan belt should deflect approximately 3/5in. (15mm) when pressed firmly at its mid point with one's thumb.Per (CHILTON repair manual 70200)

Lambros: Is that 3/5 inch a typo? My Chilton and Haynes manuals both say 1/2" to 5/8" MAX........

Also, I usually check the tension again after 100 miles or so as these belts tend to stretch (usually in the first 25 miles) and need to be adjusted tighter after they run-in.

gn

I hope we have the same CHILTON 70200 manual.I found the info on pg.2-5.I also have the"How to keep your VW alive" by John Muir and says that the belt should only deflect 1/2" to 3/4".Let me know what you think. thanks

Yup, you're right and we're both on the same page - sorry!

Got out my "Gonculator 5000" calculator and 3/5" ~= 5/8" (and both are around 15mm)

Should have done the math before and saved all this typing!

gn

Haynes Manual VW/KG '54 thru '79 says deflection at the longest run of he belt should be 1/2 inch so that shoul hold true for Alternators and Generators.

Friend of mine was doing some machining for an R&D scientist awhile back. One of the dimensions was 32/64ths inch. Puzzled, my friend checked with the PHD and inquired if perhaps this was an error? No, the PHD replied. Why didn't you just dimension it 1/2 inch my friend inquired? Because I want it to be very accurate, the PHD replied!

That's why PHD stands for Piled Higher and Deeper.
Ron

It appears that the Gates 7355 is the recommended belt. Since these are size specific and since they are also usually listed by car and year what should I buy. I'm putting together my in-car emergency kit and a fan belt is #1 on the list.

Oh no I just looked out the window and we are having our first rain of the year. Damn weather man said it was supposed to warm and clear today.

Troy:

Yes, the Gates 7355 is the recommended belt, ESPECIALLY for an engine bigger than stock. Go to the parts store and ask specifically for a "Gates 7355" belt.

It should not matter what year, make and model car you have.....all the counter person needs to know is that you want the Gates 7355. If he/she balks or offers their brand equivalent, then politely say no and, if they don't carry Gates belts, find a place that does.

Accept no substitute! If it doesn't have "Gates 7355" embossed onto the outer surface, don't take it. (BTW: CarQuest parts stores after-market Gates belts with CarQuest wrappers, but the belts still say Gates 7355 on them).

Proper installation allows 1/2" horizontal deflection with your thumb against the belt half-way between both pulleys. Check it by turning the engine over for a few seconds when you install the belt and then check deflection. Add/subtract fan pulley spacers to get to the desired deflection. Re-check and re-adjust after 25 miles or so.

Don't sweat the rain.......you've only had 3" in the last 12 months - you folks are about due........

gn

I had a former neighbor (engineer)that was installing a Ham radio antenna on the roof top and couldn't figure out that three guide wires spaced evenly would each be set in place at 120 degrees !

Anoth way to confirm there is correct tension and play in a fan belt is that you can grasp it between your thumb and index fingers, turn it 1/4 of a turn amd no more.