Breaking Fan Belts

[Phil Waterman]

On the way to a parade this weekend I shredded two fan belts on my C60 driving on the highway at speedometer speed of 50 mph I was 70 miles into a 80 mile trip when suddenly I noticed that amp meter was showing discharge followed quickly by smell of antifreeze. Pulled over into a weigh station and discovered that the fan belt was shredded. See photo. No big problem carried a spare old fan belt. After letting it cool off replaced the belt and check radiator which was down a little. ( The expansion tank had expanded as its vent was to small to take the rapid increase in flow coming out of the radiator.) Started engine everything seemed fine 3 miles down the road same thing happened. Yes I had checked to see that the fan/water pump and generator were turning freely. Pull down off ramp and stopped good Samaritan took me to the nearest auto parts store and luck again they had the belt. Back to the truck, replace belt again decided to head home on the back roads every thing seemed fine up to about 40 mph then could hear the fan changing tone like it was slowing down. When down shifting it squeals.

Any thoughts on how to check for cause?

[Col Tigwell]

With my limited experience, short fan belt life is often associated with either excess pully wear, or the belt is not the correct cross section for the pully grooves.

Many think that so long as the belt is in the grooves all is well.

This is not so, the outside of the belt, (the place where normally the belt markings are placed) must ride above the pulley flance. The distance should be about one to two MM.

If this does happen, then the belt tends to overheat, which causes the strong part of the belt, (which again is the outside) to ride down in the groove, which again places pressure on the belt.

I would try temp. fitting another belt, and observe if all belt protrusions are the same. If they are not then it could mean that one or more of the pulleys have worn too bad for use.

If they are all below the pulley groove, it means you will have to go to a wider belt. Belts come in different grrove widths, and you should be able to go up in size at a good belt stockist. My experience shows that cheaper belts are not worth buying, and you need to seek Dayco or Gates belts for maximum life.

Taking a pulley off the truck, when you do your selection, so you can trial and check the belt riding in the groove, will assist you in your venture.

Please ensure the belt btension is correct, and also check that there is no drag coming from the generator or water pump, if their bearings are getting tired, they too could be creating extra drag, which will make the belt overheat too.

I hope I have given clear enough points for you to look at.

Regards

Col Tigwell

[rob love]

If nothing is siezed, I would put my money on the tension being insufficient. The squealing supports this. After replacing the belts you have to run them for about 15 minutes to 1/2 hour, and then retighten them. Check it again after a couple of hours. If they are loose, they will jump the pulley and as soon as one lets go it can tangle the other one and they both go. Another indicator of a loose belt is when a belt will flip over in it's groove.

You actually got a chevy up to 50 mph? I thought only the Ford's could go that fast.

[Lynn Eades]

Have you got a bearing on its way out in your waterpump or geny. Is your geny/regulator/ battery all as they should be? There are a number of posabilities, just check everything carefully.

Originally posted by herkman
Many think that so long as the belt is in the grooves all is well.

This is not so, the outside of the belt, (the place where normally the belt markings are placed) must ride above the pulley flance. The distance should be about one to two MM.

That's interesting, however, I can think of three examples at least where this is not the case by design.

In every instance of the above, one pulley is arranged to have moveable flanges for tensioning and the (correct) belt would never approach the flange edge until utterly worn out.

The three that spring to mind are:

WWII Morris Commercials and all the civillian cars/trucks using the same engine type; in this instance the front water pump flange is threaded on the shaft and can be screwed back to increase the operating radius and therefore belt tension.

All pre-war, war-time and post war flat four VW engines have a shimmed dynamo pulley, taking one shim from between the separate pulley flanges and "storing" it as a packing piece on the outside of the flange also increases the pulley operating radius and therefore tension.

Mk.2 Alvis Stalwarts have twin fans with two belts arranged in a Y formation, the junction of the arms would be the waterpump and the vertical line represents the toothed belt drive to the pump from the crankshaft. The fan pulleys are on stepped diameter shafts having left and right hand threads; loosening the axial clamp bolts and rotating the fan will have the flanges move equally inwards or out to set the belt tension. With the fans on a separate housing unit, turning the flanges in opposite directions allows them to be aligned with the water pump driving pulley vees.

R.

[Hanno Spoelstra]

Originally posted by FV623
All pre-war, war-time and post war flat four VW engines have a shimmed dynamo pulley, taking one shim from between the separate pulley flanges and "storing" it as a packing piece on the outside of the flange also increases the pulley operating radius and therefore tension.

Indeed, works wonderfully well as long as the crank pulley and generator pulley are aligned properly, otherwise the Beetle eats belts like there is no tomorrow. Correct tension is important, mostly for cooling!

H.

[Phil Waterman]

Thanks all for the suggestions of what to check. Removed the generator to check it. Removed the brushes that are not badly worn with less then 12,000 miles on them, spun the generator up to about 1800 rpm it ran smooth and quiet, and took a long time to spin down to a stop. Generator has the sealed ball bearings both ends not little oiling caps. Strange as my HUP which is two years newer and does not have the air filter has the oiling caps. Only noticeable problem was the mounting bolt holes in both generator and bracket were both badly egg shaped, drilled them out to the next size larger and change to larger bolts.

Fan seems to turn freely with no noticeable lateral or vertical movement. Does drag more than a dry pump but that is to be expected as pump was still on the engine with full cooling system. Fan has no detectable forward back play.

All the pulleys look in good condition with the top of the belt riding nearly at the top edge (outside) of the pulley. They also look to run true.

Reinstalled generator and aligned all the pulleys by eye, need to make one of those tools shown in manual. Test ran it in the shop up to a constant 3000 rpm with no noticeable problems. Now I guess only time and another long road run will tell. Think a spare water pump and another belt are in order before getting to far from home again.

Note the affect on coolant recovery tank the vent could not vent fast enough. Where am I going to find another coffee can the same size.

Included a couple of pictures including pictures one of the fan belt spaghetti resulted.

[Bob Carriere]

Good news Phil ... you iwll not have to go out and buy a big can of coffee for the office just so you can save the can for the C30.....

Jeff and Dan at CC4 had fabricated one from aold pain can....preferrably empty.... and mounted upside down....looks very similar to the hidden can on John Skagfeld C13....

You just never know what these pictures will be good for when yo take them....

First is off the water truck of Jeff and Dan....

[Bob Carriere]

Only John can tell us if it was a similar pain can....empty sic!!!

...by chance you were not driving with the new engine muff to try it out?????

Now for Pete's sake ease off on the throttle... first you busted axles trying to do wheelies.... now racing against modern semis..
tsk tsk tsk.....

Read all the diagnostics but nothing really makes sense unless something went wrong all of a sudden..... I would have suspected a partly seized bearing.... preferrably in the pump.... maybe after cooling off... less expansion... frees up again.

One long shot would be for the crank pulley to suddenly move on the shaft.... bringing instant missalignment......maybe crazy but on my 261 it is held only by friction and key...... sounds like something intermittent.... how can it suddenly chew up two belts when it ran fine for years before?????


Since you checked the Genny so thoroughly, I would change the pump...... don't forget to try a straight edge from pulley to pulley..... the eye can be fooling you......

Let us know how you make out....

KRAP...... can't attach picture.... resized down to 40kb..... message from Forum says item to large must be
smaller than 700 x 0........

Geoff.....HELP....... something is wrong big time... her I mean small time..... how the heck can I resized down to 700 x 0 unless I am sending the image of a fishing line.... very tightly stretched...

Tek-no-low-gee.......bah!!!

[Bob Carriere]

Let's see if it works

[Lynn Eades]

The bottom of the pulley groove is shiney which it should not be.
The belt should only contact on the sides,with clearance underneath.

[Phil Waterman]

Originally posted by Lynn Eades
The bottom of the pulley groove is shiney which it should not be.
The belt should only contact on the sides,with clearance underneath.

Good eye for spotting the shiney pulley, but that was after I cleaned it on a soft wire brush. Wish I had taken a picture just as it came off the truck. In the blow-up photo the arrows indicate where the belt was riding. The belt that failed first had the segmented inside, old belt I carried as "spare" was solid back, and the eventual replacement was a new segmented inside gates belt.

One thing that I was glad of was that one of the shredds had the part number on it, because more and more parts store counter people can not find a part if it and application are not listed in the computer.

[Ponysoldier]

You might try this. Take a bar of soap and rub it on all
of the exposed surfaces of the belt,this helps reduce
heat .
Patrick