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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning Check your tensioners

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      08-12-2018, 01:21 PM   #1
Funwithdesign
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Check your tensioners

Soooo....I've had my M235i for about three weeks now and was driving home the other day when the 'charging system malfunction' message came up.

I got home and looked under the hood and sure enough, a tensioner pully had self destructed (it was lying in the bottom) and the belt had jumped (not shredded interestedly enough).

Had it towed to the dealer last Monday. They called me to say that the damage was quite extensive.

I'm picking it up tomorrow so will be interesting to see what actually happened because the belt itself doesn't look damaged (I've seen the horror stories of shredded belts being sucked past the crank seal). I'm curious to know what actually got damaged.

Anyway, check those belts and tensioners, could be a nasty shock for a cheap maintenance item.
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      08-12-2018, 02:21 PM   #2
Pray for Mojo
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What year and mileage?
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      08-12-2018, 02:43 PM   #3
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Quote:
Originally Posted by Pray for Mojo View Post
What year and mileage?
2015 ~60K KMs
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      08-13-2018, 09:31 AM   #4
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that's crazy man! I think I seen a few posts on the 3 series forums that had jiggly tensioner but I haven't seen the same for 2 series yet. Subbing for updates, all the best man.
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      08-13-2018, 09:37 AM   #5
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any help on what I/we should be looking for? I'm not well versed in tensioners
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      08-13-2018, 11:20 AM   #6
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Quote:
Originally Posted by delvec03 View Post
any help on what I/we should be looking for? I'm not well versed in tensioners
go to the 3 series forums under the n55 section and there's a post right on the first page. Apparantly, the tensioner pulley should not jiggle at all while idling. Mine jiggles a bit and I had mine checked at my last oil change and they said it was fine. I might replace it for preventative measures though.
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      08-13-2018, 11:39 AM   #7
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Mine jiggles too. That is part of the design as it's spring-loaded. It shouldn't jiggle wildly, but it will jiggle a few millimeters in each direction. One should should check the belt tension every month or so when doing a cursory underhood check for leaks, etc. The belt should only deflect a 1/4" or so with moderate finger pressure on a wider spread of the belt.
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      08-13-2018, 12:08 PM   #8
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Quote:
Originally Posted by XutvJet View Post
Mine jiggles too. That is part of the design as it's spring-loaded. It shouldn't jiggle wildly, but it will jiggle a few millimeters in each direction. One should should check the belt tension every month or so when doing a cursory underhood check for leaks, etc. The belt should only deflect a 1/4" or so with moderate finger pressure on a wider spread of the belt.
that's what my shop said as well. However, in the 3er forums, there is a pretty big difference once replaced. There is no jiggle at all but that's on a brand new component so who knows what happens after some mileage.
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      08-13-2018, 07:58 PM   #9
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just checked mine out. def some giggle. nothing constant, which makes me think I'm ok.

checked it the n55 form, their tensioner looks different than ours. I can't quite find all the proper holes on mine. anyone have good info? pics Maybe?
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      08-13-2018, 08:17 PM   #10
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Quote:
Originally Posted by delvec03 View Post
just checked mine out. def some giggle. nothing constant, which makes me think I'm ok.

checked it the n55 form, their tensioner looks different than ours. I can't quite find all the proper holes on mine. anyone have good info? pics Maybe?
so, contrary to my previous post, I bought a new belt tensioner and belt.

...wish me luck.

CDV
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      08-13-2018, 08:36 PM   #11
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Well I picked it up. It's all good but I'm not 100% clear on what the issue was yet, the tech hadn't written up all the notes. They are sending me the breakdown but apparently as I had read, there were bits inside the engine which involves taking off the valve cover and dropping the oil pan for starters.

Will update when I find out.

The car is good though, no issues. Thankfully a warranty fix (mine is up in January 2019) and I do have an extended one (for the first time ever).
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      08-13-2018, 10:19 PM   #12
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Quote:
Originally Posted by Funwithdesign View Post
Well I picked it up. It's all good but I'm not 100% clear on what the issue was yet, the tech hadn't written up all the notes. They are sending me the breakdown but apparently as I had read, there were bits inside the engine which involves taking off the valve cover and dropping the oil pan for starters.

Will update when I find out.

The car is good though, no issues. Thankfully a warranty fix (mine is up in January 2019) and I do have an extended one (for the first time ever).
glad all is well. Were you driving it hard when it happened or was it completely random?
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      08-13-2018, 11:19 PM   #13
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Quote:
Originally Posted by Funwithdesign View Post
Well I picked it up. It's all good but I'm not 100% clear on what the issue was yet, the tech hadn't written up all the notes. They are sending me the breakdown but apparently as I had read, there were bits inside the engine which involves taking off the valve cover and dropping the oil pan for starters.

Will update when I find out.

The car is good though, no issues. Thankfully a warranty fix (mine is up in January 2019) and I do have an extended one (for the first time ever).
how does one get belt pieces inside the engine?
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      08-14-2018, 12:06 AM   #14
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Quote:
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glad all is well. Were you driving it hard when it happened or was it completely random?
Nope cruising (read stuck in traffic ) on the 401, didnít even know anything happened until the error message came up.
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      08-14-2018, 12:08 AM   #15
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Quote:
Originally Posted by delvec03 View Post
how does one get belt pieces inside the engine?
The crank pulley is so close to the block that if the belt shreds then it can get stuck between the pulley and then suck past the seal.

A fair number of horror stories on the forums with the n55 about this. Not sure that makes it prevelant but something to check, cheap insurance.

My belt didnít get shredded but apparently something did end up happening.
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      08-14-2018, 12:25 AM   #16
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Mine shakes pretty bad, going to replace.
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      08-14-2018, 09:03 AM   #17
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Quote:
Originally Posted by Pray for Mojo View Post
Mine shakes pretty bad, going to replace.
Good idea.

For a pretty much bomb proof engine (compared to some other BMW engines in the past) it's scary that a $100 part has the potential to cause this much damage.

Apparently though this isn't isolated to BMW, as engines have been getting more compact and the tolerances smaller, this is something that is happening to others too.
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      08-14-2018, 12:00 PM   #18
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I'm going to change the idler pulley as well, since that's supposed to be replaced at same time as the belt. I'm at 70k km, so this stuff is due for replacement soon anyhow.
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      08-15-2018, 01:27 AM   #19
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Changed mine tonight in less than 30 mins. For whatever reason the tool sizes are a bit different on our cars (Might be a 2014 thing). You need a T55 torx bit and a E14 instead of the T50 and E10/12 the F30 guys are referencing in the instructions. I also used a 5/32" R lock pin for a trailer hitch to lock it out of tension. Didn't do the idler pulley yet, since it's on order and mine felt fine on inspection. Used these instructions from Badbread http://badbread.com/tensionerdiy/ with the different sizes for our cars. He pulled the lock pin out of the new tensioner with force, but if you crank the new tensioner the same way you lock the old one the pin comes right out.
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      08-15-2018, 07:35 AM   #20
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Now that I take a closer look at what actually happened, it was the idler pulley that broke off on mine. The tensioner was probably also gone too as they replaced all the pulleys.
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      08-15-2018, 11:34 AM   #21
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Quote:
Originally Posted by Funwithdesign View Post
Now that I take a closer look at what actually happened, it was the idler pulley that broke off on mine. The tensioner was probably also gone too as they replaced all the pulleys.
how did you discover that's what failed first and how do you check for these in general? Is it just checking for belt deflection?
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      08-15-2018, 02:21 PM   #22
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Quote:
Originally Posted by amw896 View Post
how did you discover that's what failed first and how do you check for these in general? Is it just checking for belt deflection?
Mine was obvious, the charge malfunction error came up when I was driving and when I looked the pulley was broken off and the belt was off. Most people have heard a noise and the belt gets shredded.

You don't want to get to that part.
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