Problems with Belt slipping OFF!?

[Virg///M3]

I have been having this problems for years now. It seems that the main belt, not the A/C, slips off and sometimes breaks. And the reason I say for years is becasue it only happens when I drive the car hard.

The car is an E36 M3 ('97) with 81K miles on it. Just recently I had the idler tensioner replaced & installed underdrive pulley (Power steering & water pump) to see if that was the problem but a few days of driving it hard & the belt comes off, but this time it broke because it got tangled up with the fan.

MY QUESTION IS, BEFORE I REPLACE ALL OTHER PULLEYS & TENSIONER FROM THE DEALER AS ALWAYS, IS THERE SOMETING ELSE THAT CAN GO WRONG OR IS THERE A SPECIFIC PART THAT I SHOULD REPLACED BEFORE SPENDING ALL THAT MONEY?

[corwyn]

Have you replaced your water pump? The metal-impeller one that replaced the original plastic one had this nasty tendency to have a bearing failure, so the pulley wouldn't stay in the right spot. It probably wouldn't hurt to take a look at the pullies while the engine is running, to make sure they're all staying in line, especially when you blip the throttle a bit to put some extra tension on the belt.

Other than that...are you sure you have the correct size of belt?

[Virg///M3]

Originally Posted by corwyn

Have you replaced your water pump? The metal-impeller one that replaced the original plastic one had this nasty tendency to have a bearing failure, so the pulley wouldn't stay in the right spot. It probably wouldn't hurt to take a look at the pullies while the engine is running, to make sure they're all staying in line, especially when you blip the throttle a bit to put some extra tension on the belt.

Other than that...are you sure you have the correct size of belt?

Sorry I forgot to mention that, I did change the water pump. I have been getting the belts at the dealer with my VIN number several times at different dealers. I don't actully know the size of the belt but I don't think all of them are going to sell me the wrong size belt. The new Underdrive pulleys came with a specific belt , 13/16" x 63-5/8" OC (20mm x 1616mm OC).

Thansk for the quick response, CORWYN.

[corwyn]

Originally Posted by Virg///M3

Sorry I forgot to mention that, I did change the water pump. I have been getting the belts at the dealer with my VIN number several times at different dealers. I don't actully know the size of the belt but I don't think all of them are going to sell me the wrong size belt. The new Underdrive pulleys came with a specific belt , 13/16" x 63-5/8" OC (20mm x 1616mm OC).

Thansk for the quick response, CORWYN.

Unless they only have belts for stock BMW sizes and the closest one to yours is too large... But I'm cynical

It doesn't hurt to doublecheck the belt size yourself (probably printed on the smooth side of the belt somewhere), or even just replace it yourself to make sure you have the right size. One test would be to go to your dealer parts counter and ask for the 20x1616 to see if they can get you the right size or if they give you something bigger.

And like I said earlier, check how the pullies all look when the engine's running and you rev it a bit. Make sure everything's staying in place.

[Virg///M3]

OK, Thanks again. I am going to the shop now to inspect everything including the size of the belt. Maybe we can try a smaller size if we can squeeze it in there.