Alternator Belt

[junglestylz]

I am having a slight isue with the alternator belt on the new 1991 318is. The main problem is that they keep breaking. The belt aren't over tightened, and the alternator isacting as it should. When I throw a new belt on, it lasts about 50 miles before it loosens up. The alternator doesn't move when this happens though. So when I readjust it to keep the belt tight enough to keep it from squealing, I soon run out of space on the bracket. I figure that it it either a pulley, alternator size, or the bracket itself that is causing the problem, but would like to know if anybody else has had this problem, and what actions were taken to remedy it. I was also thinking that it may be a cracked pulley. Any help would, and will be very, VERY appreciated.
Thanks in advance, and a merry christmas and big ups to all.
Seth

 

[Tom]

My guess would be the pulley as well. At first I thought that you may have overtighten the belt which caused them to break. Try replacing the idler pulley first to see if that remedies the problem.

 

[junglestylz]

I was told earlier that it could possibly be worn alternator bushings. I found some urethane bushings at Bavauto, so it might be worthwhile to replace them anyway. For $4.95 each, it couldn't hurt. I need to order a new adjustment nut anyway, so I would make an order for that. I am gonna pull the damn thing apart tomorrow to try to figure out exactly what the problem may be. I am definately gonna check the idler pulley.

 

[Rukus]

If your pulley is cracked, it won't be symmetrical and it will cause the belt to have tight and loose places on the pully, causing it to gradually stretch and wear out. If the bushing are gone, the belt would most likely have noticeable "burn" wear, and wouldn't likely stretch out like it is, it would just burn off.

atleeast thats what i think. My 318i had a similar problem, i thought i had it tightened properly, but it wasn't, it has to be JUST RIGHT, it seems, or the belt will slip off. Because i had it too tight once and the belt came off and i almost cooked my engine (stupid faulty grounds in dash didn't let me read the temp guage peroperly) and too loose is obvious results.

 

[mikev]

I have a boat with a marinised 4.3l V6 we have to tighten up all the belt all the time. one problem we kept having was the altenator slipping due to crap bolts and washers (now fixed) the problem is that the when it got loose deposits of rust (and rubber from old belts) literally cut through the belts. check the condtion of you pully, if the paint is flaking or there are rust deposits then sand them down with a bit of wet 'n' dry. and the re-paint them. also like Rukus says they do have to be just right not tight not loose. i don't know the exact measurment but on the boat its between 3/4 and 1 inch of give when "fully tightened".

 

[junglestylz]

I always make sure as far as tightening the belt according to the Bentley Manual to the best of my ability. There is a fair amount of cooking on the sides of the belt. I found the urethane bushings, and I need to order the adjustment nut anyway, so I would rather get it all in one swoop. I am gonna pull the aternator, and the idler pulley this weekend and refinish them as you suggested. Thank you all very much for the insight and suggestions.
Big ups,
The junglist

 

[junglestylz]

It is the fan pulley. It is all bent to shit.