Unusual alternator belt problem

[Aidan]

Hi guys, Had my 940 tic for excactly a year now, and I have a strange problem with the alternator belt, the teeth keep breaking off the belt and it ends up shredding itself to bits, since I got the car I've put 6 new belts on it, so roughly every 2,500 miles. I've done all the usual, checked all the pulley's etc for damage, alignment etc, there all fine, used all different makes of belt (Volvo origional, Gates etc) tried running the belt loose, tight, in between,,, still keeps breaking them, any idea's, thanks.

[v8volvo]

That is an odd one.

One of mine went through a couple belts after I replaced the motor with one that had sat for a while and had rust on the crank and alt pulleys.... the rust wore the belts down quickly, but now that the rust is gone the 3rd belt is lasting. Doesn't sound like your issue, though.

Alternator bearings OK? Are the rubber bushings that mount the alt in its bracket in solid shape? Those often wear out and cause the alt to sit crooked, which can be hard on the belt.

You might want to put up a picture of what your setup looks like -- all of my experience is with the US style setup, which has the alternator mounted down low on the right side of the car, above the oil filter. If yours is the later Euro-spec style with the alt mounted up high on the left side (where the power steering pump is on our cars), then I'm afraid my help is not worth much...

Any weird noises, or does this just happen quietly? Is the crank pulley/harmonic balancer in OK shape? The balancer is a 2-piece design with a layer of rubber sandwiched in between, and I have seen on other cars where that rubber layer gets old and shrunken and then it makes the crank pulley wobble and throw the belts off... worth checking to see if the 2 halves of the unit can move or if it looks like anything is wobbling when the engine is running.

[Aidan]

Hi, and thanks for the reply, I've tried all that and checked all the components, everything is good. all the pulleys run true, the altenater mounting bushes are nice and solid, the alternater sits perfectly in line, all pulleys have been checked for any damage or digs, all ok. Mine is the Euro set up, alternater is above the power steering pump. There are no noises when this happens, it just quietly eats the teeth. Looking at the pulleys when the engine is running shows no wobbling, even up to 5,000 rpm, everything runs fine and the crank pulley has no movement between the two halfs and the water pump has no pulley movement either. I even asked the mechanics at the local Volvo dealer and none of them have come across this before, I'm a qualified mechanic myself but this has got me totally baffled. The engine has just over 120k genuine miles, serviced at Volvo from new so it has been looked after properly..... As an aside, my power steering pump bushes are worn to the extent you can visually see the "twist" in the pump pulley and it's 11mm out of true but I dont have any problem with the power steering belt breaking teeth, so that rules out any crank pulley problem causing the fan belt problem, it sure is a weird problem. The only other thing I can think of is if the alternater pulley is too small a diameter and causes the teeth to contact each other as they go round the pulley,,,, it does seem to be a very small pulley diameter wise but unfortunately I dont have a means of comparing it to another D24Tic as their very rare over here, would you, or anyone else know what the diameter of the alt pulley is?

[Slobodan]

I had this same problem on a customer's car. It might not be what your problem is but its something to consider.
The alternator would start working harder and harder because of a build up of resistance that was happening at the B+ hook up on the back of the alternator. This was happening because of a very old and corroded ring terminal connector. Solution: Cut back about an inch or so on the cable and crimped a Copper ring terminal connector on instead of the aluminum one. Problem solved.

[Aidan]

At this point I'm willing to consider anything so I'll pull the connector and see what we got

[ian2000t]

Will measure my UK 760 Dtic alternator pulley when I get a few minutes.

[michaelovitch]

Are you sure you use the appropriate belt ?

what are the dimensions of it ?

alt pulley dimensions on a bosch 80 amps is 41 mm (1.6 inch) (the inside smaller groove where the teeth are)

the 60 amps of the 240 are smaller,im sure.

the belt must be 9.5 mm or 10 mm wide (0.39 inch)

it's the same for the 240 740 or 940 seen the crank pulley is the same.

i don't think the size of the pulley is faulty.

[v8volvo]

Inspect your pulley again.

I am just remembering a case of a customer's 245 Diesel a year or two ago that came in with alternator failure to charge. I put a new Bosch reman unit on, with a new Conti belt, and sent it away. The car was back the next week... alt was fine but the belt was gone, completely missing. Checked out the alt pulley and discovered there was a bend in it, like someone had whacked the front flange of the pulley with a hammer. The pulley consequently had a narrower point in it, which was evidently pinching and stretching the belt once every 360 degrees of alternator rotation. The belt was destroyed in short order.

I still had her old core unit around so I swapped the pulley off of it, which was in fine shape... put on another new belt and the problem did not return.

You seem to have exhausted all the typical causes of this sort of problem on these cars.... now you get to start looking for the weird ones. :rolleyes: :)

[Volvoist]

Another thing to consider: make sure the glow plugs are turning off. I suspect this lead to the failure of my 244 diesel engine that I have since rebuilt. When I removed the alternator belt, it was very worn out and the teeth were missing. All of this occurred in 4500 miles. I suspect the glow plug system stuck on. That will cause the alternator to work a lot harder, and cause belt wear in short order.

[ian2000t]

Another thing to consider: make sure the glow plugs are turning off. I suspect this lead to the failure of my 244 diesel engine that I have since rebuilt. When I removed the alternator belt, it was very worn out and the teeth were missing. All of this occurred in 4500 miles. I suspect the glow plug system stuck on. That will cause the alternator to work a lot harder, and cause belt wear in short order.

That sounds likely on yours - never seen glowplugs melt before. Did you ever put any pics up of your engine failure?

[Volvoist]

That sounds likely on yours - never seen glowplugs melt before. Did you ever put any pics up of your engine failure?

Nope, never did. I had some pictures, but have been too busy to do so. I have since rebuilt the engine.