[norb2011e92]

Car is a 2011 335i E90 LCI with the N55 engine. We noticed an oil leak and identified the front crank shaft seal was busted. Replaced it and that fixed the leak. At the same time we noticed the belt was a bit ripped/shredded to we replace it and thought all was good but not so much.

New belt was installed and right away it started eating away at it. We drove about 4 miles and half the belt is shredded away. All of the pulleys (look) ok with visual inspection but who knows. All have been tighten down and take off and reinstalled to make sure there are no belt particles left somewhere.

Any thoughts or ideas fellas?

just found this video and I have a suspicion my belt was not put on this way when I got the car

https://l.facebook.com/l.php?u=https...N01HIMyIarPP-g

[uber]

I've had a 328i with similar issues. I've probably replaced the belt 4 times and the pulleys twice. It ended up being the harmonic balancer causing all the issues.

Before looking at the harmonic balancer though, you should ensure your oil filter housing isn't leaking because that will definitely cause a belt to fail before anything else.

[ky0u]

Is your power steering pump fully secure? Like no loose bolts?

[norb2011e92]

Originally Posted by uber

I've had a 328i with similar issues. I've probably replaced the belt 4 times and the pulleys twice. It ended up being the harmonic balancer causing all the issues.

Before looking at the harmonic balancer though, you should ensure your oil filter housing isn't leaking because that will definitely cause a belt to fail before anything else.

if the oil filter housing is leaking, shouldn't I see traces of oil on the belt or pulleys?

[Ozzie335i]

If you end up yanking the harmonic balancer if only for a look see you might consider installing that 150 dollar cover to keep the belt from being sucked into the engine.

[whyzee125]

I would replace all pulleys, check the power steering pulley, and see if that does it. N55's are notorious for needing harmonic balancers too but that's the least likely IMO bc while they bounce up and down, I've never seen one wobble side to side which is what would cause a belt to shred.

[Blksmth88]

Did you ever solve the issue? Im asking because i had the same problem with my car and my gah what a head ache i had to go through to sort this problem. grab some popcorn and sit back cause heres a story for you. READ LAST 2 PARAGRAPHS IF YOU WANT TO SKIP MY LONG WINDED STORY AND GET TO THE SOLUTION.

First when i bought my 2012 e92 N55 6mt with 60k miles the PO had just did a pulley kit gaskets and seals and fresh belt. all looked well and fast for to 2 months later. my girlfriend and i decide to drive to a road about 2 hrs from us called the dragon. its at the western tip of NC and TN border. the event was called Mvading the dragon if youd like to check it out, but anyways its a 2 day long thrash fest on your car and suspension to put it lightly. Tons of hard tight curves and long sweeping straights for everyone to really push and see what they and their car is made of. Long story short we drove out raised hell and met some cool people and had to drive home for work the next night. all went well and the next morning comes and i head out to the car and start it up to hear a little belt squeak. I didnt think much of it as i had beaten the car all day long the previous day and it cleared up after a few mins of idle.

Ok heres where it gets fun. I drive 1 mile.. yes 1 mile from my house and my belt shreds to the point of 2 ribs holding it together and arm full of shreds fill the front of the engine bay. I get it all dug out and limp the car home on the remaining string of belt and then I head out and grab a new one from the auto parts place. Get home and go to put it on and its not fitting well but its on.. I also notice my tensioner looks a little crooked but i assume its my eyes playing tricks on me. So i get it all back together and drive the car 50 miles round trip to work. When i get back home i smell hot rubber.. So i go back to the belt ant too my surprise it has started eating one of the tensioner pulleys and began to come apart its self... Great now im buying a replacement pulley set AND another belt... Only its taking me forever online because i cant find anything that matches my car. For some reason every diagram i see for the N55 shows 8 total pulleys and mine only had 7 if memory serves correctly.. This left me scratching my head for a solid 3 days. I finally just typed my cars info and exact model in on a reputable site and hoped it would be the right bits for my car. At the end of three days i get my parts and yet another belt and i go to put it on and though it is the same size it is way too loose.. Im losing my mind at this point my pulleys arent the same as other 335s and now my belt that fit the other tensioner which is now broken is some how too long on the new tensioner. It worked before but not now!!???

So i decide to rip the whole system apart for what must be the 8th or 10th time to figure this out when i finally see my issue. Some how at some point one of the ears that the idle pulley bolt screws into had snapped off, making it impossible to mount one of the pulley replacements to the front of the engine. Im assuming either in reassembly, an engine replacement with a wrecked one or just ignorance it had gotten damaged idk. its the pulley below and to the left of the alternator. luckily this one ear is attached to the timing cover so it is replaceable. However i neither have the time or money to rip the front of my engine off and source a replacement or remake the ear and weld it on. Im also completely stumped as to how the last belt worked at all in this configuration because i could not find any routing for the belt that would use up enough slack to get it to work. my only guess is the last owner had ghetto rigged the tensioner into a position that worked at the time but eventually fatigued everything enough till it finally let loose. (side note: I flew from North Carolina to Delaware to buy this car. I drove it all the way back home... Drove it for 2 months all over... Thrashed it all day for hours on the curviest rode around with 50 other BMW lunatics. A whole 2 hours away from my house only to have the belt finally give up a mile from home.. What i thought was bad luck might have been the luckiest event of owning this car period.)

So at this point now that i have discovered the problems (broken pulley mount and Bent tensioner bolt combined with broken tensioner) i find my solution. I had to use the new tensioner and 2 of 3 pulleys the kit came with. I had to make 3 trips to the local Carquest where i swapped out different length 7 rib belts until i found one that was just the right length. It had to pull the tensioner with out over stretching the spring, but also not have too much slack... That belt was for a 1997 honda accord lol. works like a charm and quiet as a mouse on 7 pulleys. I saved the packaging should i ever have to replace the belt again.

With all that said. i would suggest from my 10 days of BMW belt hell. First with the belt off check each pulley for wear or play. If they all check out good make sure your tensioner is straight. even if you need to take it off make sure its in good shape and that the bolt isnt even slightly bent, this is what caused my second belt to shred the bent bolt had the belt running across the idler pully just crooked enough to wear rib groves in the smooth pulley. it was also tracking to one side of the pulley or slightly off the edge. it shouldnt do any of that at all. Good luck to you! I have pics on my computer at home ill add to this when i get home.