I’ve had a Mini Countryman 2014 with an n18 for a couple years. Recently had a belt that only lasted 20k miles before shredding. The next only 5k and the most recent belt lasted maybe 20 miles before breaking. I’ve recently replaced the tensioner but any suggestions on what else to check? The pulleys seem to solid but I’ve also noticed some oil and smoke from the passenger side.

 

The belt drives the AC compressor and alternator directly. Indirectly, the belt drives the water pump friction wheel. Depending on the failure mode of the belt would determine which component might be causing the destruction. If the inside of the belt is excessively worn, check the compressor and alternator. Maybe one of those components is seized? If the outside of the belt, check the friction wheel assembly to see if its getting worn.

 

Neither pulley is seized on the AC or the alternator. I’m getting wear on the inside of the belts prematurely. Could it be a harmonic balancer? I am at 120k miles.

 

Try cleaning out the grooves in each of the pulleys. Maybe chunks of road "stuff" imbedded in them. Then the obvious --- are you using the correct belt? Width and groove qty / size is critical.

 

I've had this problem on mini race cars. Others I know have had the same problem on supercharged or turbo BMW race cars etc. Commonest culprit is something wrong with the on of the pulley wheels, eg a sharp edge, crack, chip on one of the grooves, or a something stuck in the groove. Have a very close look at the pulleys. The other thing is something very slightly out of alignment, putting undue stress on things. Look at the car idling, and try and verify everything is straight and true.

I also once had a faulty tensioner out of the box.

 

I have had rather mixed results with different brands of belts. The factory fitted Dayco looked better when replaced at eight years of age than an SKF belt at two (in regard to the inside drying out and cracking).

A belt by Continental still looks new at roughly two years of age (though its uneven outer surface causes slight knocking when driving the water pump).

A relative working for years now at the service department for a large public transport coorporation in Greece also told me that when they switched to SKF belts for their busses, (very) premature failures increased rapidly, forcing them to refuse SKF belts from their supplier.

 

I have been going through the same issue for about a year. The only main changes are the ac compressor which might be aftermarket. Everything except for the compressor and tensioner have been replaced. It will be ok until you give it the beans then it will slip off and hopefully not take out the friction wheel. Each belt is missing inside ridge but not completely broken

 

Yes their were two belts length based off the A/C size. What might have happened is a belt was changed at one point to the wrong size?

https://www.northamericanmotoring.co...lley-size.html

Also check the pullies and the tensioners, look for wear and rub marks.

 

the belts seem to be ok until I launch hard and then it slips off. Most of the time the first row of thread towards the block are partially missing, but still have 4 valleys and 5 raised points. Only the part towards blocked gets frayed and can still be used. Weird. Would belt slip of if tensioner was hold tight enough? Does the aftermarket ac compressor sit to far toward and under pressure slips it off? Not sure. If I cannot figure this out I will end up replacing the ac compressor for oem and tensioner in case.

 

Yes, but you can check the part number on the aftermarket A/C and I can cross to see what belt.

Other then that you have to have someone look at it and see if install problem or gap. That's maybe waking the belt off if that makes sense. All the pulleys and systems should be straight, if one if off at an angle it can "walk the belt off" with heavy load.