Is this Belt Tensioner bad?

schriss · 09-24-2019, 03:04 PM

I was looking at engine bay more closely today and see this belt tensioner pulley looking possibly crooked and belt looking like it's partially off, getting dangerously close to that big metal ring below it.
What do you guys think? Can just the pulley be replaced or more like entire belt tensioner? At least belt looks like zero cracks.

Explorerlyon · 09-24-2019, 03:16 PM

Replace the tensioner, bolt that holds the tensioner and your belt. The pulley and the tensioner come together as a unit. Cost you around $100 in parts. This is an easy diy.

schriss · 09-24-2019, 03:37 PM

Quote:

Originally Posted by Explorerlyon

Replace the tensioner, bolt that holds the tensioner and your belt. The pulley and the tensioner come together as a unit. Cost you around $100 in parts. This is an easy diy.

That's what I thought... ordering parts now.
I'll get Febi tensioner and as for belt, will this be fine: 6PK1830 CONTITECH (RealOem tells me to get 6PK1827)
I notice OEM BMW is also Contitech but it is 1827mm while anything on the market is 1830mm... 3mm difference. Wondering if they did this so more people would go buy expensive belt with BMW logo on it?

ctuna · 09-24-2019, 03:44 PM

Could you put up and after change picture?
Looks like I can kind of see it biased toward the outside
and little fraying in the same spot.

Ozwerks makes a belt fail shield now.
for all models broken belt
https://www.e90post.com/forums/showthread.php?t=1305990
http://www.bimmerfest.com/forums/sho....php?t=1231881
http://www.e90post.com/forums/showpo...3&postcount=23
http://www.e90post.com/forums/showthread.php?t=1477111
https://www.oxwerkzperformance.com/and they are mostly out of stock.

marvinstockman · 09-24-2019, 07:40 PM

I just changed mine for the same reason, but I also changed the idler pulley.

I got the tensioner, idler and Conti belt from FCP for around $100.

k04 · 09-24-2019, 10:32 PM

Just did this a bit ago, super easy. I sourced all the parts for roughly $50 on Ebay. All OEM parts and a Goodyear belt.

schriss · 09-25-2019, 03:40 AM

Quote:

Originally Posted by ctuna

Could you put up and after change picture?
Looks like I can kind of see it biased toward the outside
and little fraying in the same spot.

Ozwerks makes a belt fail shield now.
for all models broken belt
https://www.e90post.com/forums/showthread.php?t=1305990
http://www.bimmerfest.com/forums/sho....php?t=1231881
http://www.e90post.com/forums/showpo...3&postcount=23
http://www.e90post.com/forums/showthread.php?t=1477111
https://www.oxwerkzperformance.com/and they are mostly out of stock.

So it looks like having that pulley getting crooked more and more and belt being 2mm off the pulley was a disaster just waiting to happen. If it went a little bit more off it would be rubbing on crank pulley.
I have seen the belt shield thingy, but nowhere it says to be compatible with N53. I would assume it is, but doesn't say so. Nice thing to have, weird it's not mass produced cheaply as just a piece of metal.

MightyMouseTech · 09-25-2019, 05:14 AM

Damn. Good thing you caught that. That was really close to coming off.

schriss · 09-25-2019, 06:20 AM

Quote:

Originally Posted by MightyMouseTech

Damn. Good thing you caught that. That was really close to coming off.

Scary to think I was on a highway going like a rocket for 1 hour trying desulphate, just 1 week before I noticed this.

schriss · 09-29-2019, 02:13 AM

Took old one off, shiny part on the pulley is where the belt was touching it.

Efthreeoh · 09-29-2019, 06:31 AM

Quote:

Originally Posted by schriss

Took old one off, shiny part on the pulley is where the belt was touching it.

I'm sure it wasn't intentional, but neat photo.

schriss · 10-06-2019, 02:23 PM

New belt tensioner is on. Also, the belt was original BMW, seems like it was the original, never changed. Brand new contitech is on.

mainbearing · 12-10-2022, 05:22 PM

Had a belt walked 1/3 off the pulley problem this weekend. Turned out to be a failing mounting bolt. The AL9 aluminum bolt was not strong enough. Makes me wonder how much of the problem was the bolt failing and not the assembly's fault.

My post here:
https://www.e90post.com/forums/showthread.php?t=1976331

And pics:

Failing bolt on top, against a new bolt below:

mgmavant · 12-10-2022, 09:52 PM

I wonder if that bolt was reused from a previous tensioner replacement. Those bolts need to be changed once they are torqued down to the proper torque. At any rate, good thing you caught it before it failed!

mainbearing · 12-10-2022, 10:38 PM

Yeah, if this engine ate the serpentine belt I will just dump it for an Audi anyway.

This failed bolt was a new one that came with the INA tensioner, so it was used only once and torqued-angled to spec (18 lb/ft+90deg).

Maybe the supplied bolt is of defective metallurgy. Anyway the newest bolt that went in today is a Rein. I used 17lb/ft+80deg this time. LOL. Time will tell.

mecheng77 · 12-11-2022, 06:26 AM

Quote:

Originally Posted by mainbearing

Yeah, if this engine ate the serpentine belt I will just dump it for an Audi anyway.

This failed bolt was a new one that came with the INA tensioner, so it was used only once and torqued-angled to spec (18 lb/ft+90deg).

Maybe the supplied bolt is of defective metallurgy. Anyway the newest bolt that went in today is a Rein. I used 17lb/ft+80deg this time. LOL. Time will tell.

Quote:

Originally Posted by mainbearing

Yeah, if this engine ate the serpentine belt I will just dump it for an Audi anyway.

This failed bolt was a new one that came with the INA tensioner, so it was used only once and torqued-angled to spec (18 lb/ft+90deg).

Maybe the supplied bolt is of defective metallurgy. Anyway the newest bolt that went in today is a Rein. I used 17lb/ft+80deg this time. LOL. Time will tell.

Or if you had some lube on the bolt, it could have been overtorqued.

I usually put a very very small amount of grease on these aluminum bolts so they don't gall the threads and I then use a slightly lower torque

StradaRedlands · 12-11-2022, 11:34 AM

Quote:

Originally Posted by mecheng77

Or if you had some lube on the bolt, it could have been overtorqued.

I usually put a very very small amount of grease on these aluminum bolts so they don't gall the threads and I then use a slightly lower torque

I really hate aluminum stretch to yield bolts. They always make me cringe when I'm doing the extra 90 or 180 on them...

mecheng77 · 12-11-2022, 11:40 AM

Quote:

Originally Posted by StradaRedlands

Quote:

Originally Posted by mecheng77

Or if you had some lube on the bolt, it could have been overtorqued.

I usually put a very very small amount of grease on these aluminum bolts so they don't gall the threads and I then use a slightly lower torque

I really hate aluminum stretch to yield bolts. They always make me cringe when I'm doing the extra 90 or 180 on them...

Quote:

Originally Posted by StradaRedlands

Quote:

Originally Posted by mecheng77

Or if you had some lube on the bolt, it could have been overtorqued.

I usually put a very very small amount of grease on these aluminum bolts so they don't gall the threads and I then use a slightly lower torque

I really hate aluminum stretch to yield bolts. They always make me cringe when I'm doing the extra 90 or 180 on them...

Agree I think they are on the edge of stripping hence why I reduce the torque

mainbearing · 12-11-2022, 12:50 PM

I did not use any lube or motor oil on the threads. But given the number of so-called "tensioner failures", I wonder how many of those were actually bolt failures.

Wish I kept the original tensioner, because I did not see anything wrong with it when compared to the new one. But I just changed it anyway.

These tensioner bolts are not the only problems, engine mount bracket bolts (4 on each side) are known to snap (Rein sells a set of bolts to address those). And cylinder head bolts too.

It may just be BMW's poor choice of bolt sizes and metallurgy. This engine was the first to use the stupid magnesium composite casting that saved 22 lbs. And maybe the last? LOL

Magnesium weakened the block that N54 did not use it. And engines with turbos is the way manufacturers are moving. Hopefully this magnesium joke is the last from any manufacturer. But in the mean time, yes reduced torque just a bit.

09-24-2019, 03:04 PM	#1
schriss Private First Class 34 Rep 184 Posts Drives: 2017 BMW 330e Plugin Hybrid Join Date: Aug 2019 Location: Ireland iTrader: (0)	Is this Belt Tensioner bad? I was looking at engine bay more closely today and see this belt tensioner pulley looking possibly crooked and belt looking like it's partially off, getting dangerously close to that big metal ring below it. What do you guys think? Can just the pulley be replaced or more like entire belt tensioner? At least belt looks like zero cracks. Attached Images __________________ Current: 2017 F30 330e PHEV Past: 2007 BMW E93 N53 Convertible
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09-24-2019, 03:16 PM	#2
Explorerlyon Private First Class 108 Rep 148 Posts Drives: Porsche 986 Acura TL-SHAWD BMW Join Date: May 2019 Location: USA iTrader: (0) Garage List 2007 E90 335xi [0.00] 2006 E90 330i [0.00] 2012 Acura TL SH-AWD [0.00] 2001 Porsche 986 [0.00]	Replace the tensioner, bolt that holds the tensioner and your belt. The pulley and the tensioner come together as a unit. Cost you around $100 in parts. This is an easy diy.
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09-24-2019, 03:44 PM	#4
ctuna Lieutenant General 1911 Rep 13,104 Posts Drives: 325xi 06 wagon MT Join Date: Jan 2010 Location: Santa Cruz, Ca iTrader: (0)	Could you put up and after change picture? Could you put up and after change picture? Looks like I can kind of see it biased toward the outside and little fraying in the same spot. Ozwerks makes a belt fail shield now. for all models broken belt https://www.e90post.com/forums/showthread.php?t=1305990 http://www.bimmerfest.com/forums/sho....php?t=1231881 http://www.e90post.com/forums/showpo...3&postcount=23 http://www.e90post.com/forums/showthread.php?t=1477111 https://www.oxwerkzperformance.com/and they are mostly out of stock. Last edited by ctuna; 09-24-2019 at 04:27 PM..
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09-24-2019, 07:40 PM	#5
marvinstockman Major 399 Rep 1,078 Posts Drives: 2011 BMW 328i Join Date: Aug 2015 Location: Rockville, MD iTrader: (0)	I just changed mine for the same reason, but I also changed the idler pulley. I got the tensioner, idler and Conti belt from FCP for around $100.
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09-24-2019, 10:32 PM	#6
k04 Private First Class 22 Rep 195 Posts Drives: 320i Join Date: Mar 2014 Location: lv, nv iTrader: (0)	Just did this a bit ago, super easy. I sourced all the parts for roughly $50 on Ebay. All OEM parts and a Goodyear belt.
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09-25-2019, 05:14 AM	#8
MightyMouseTech Major General 4338 Rep 6,196 Posts Drives: 13 135i 6MT LeMans Blue MSport Join Date: Feb 2013 Location: Ottawa, Canada iTrader: (0)	Damn. Good thing you caught that. That was really close to coming off.
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09-29-2019, 02:13 AM	#10
schriss Private First Class 34 Rep 184 Posts Drives: 2017 BMW 330e Plugin Hybrid Join Date: Aug 2019 Location: Ireland iTrader: (0)	Took old one off, shiny part on the pulley is where the belt was touching it. Attached Images __________________ Current: 2017 F30 330e PHEV Past: 2007 BMW E93 N53 Convertible
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10-06-2019, 02:23 PM	#12
schriss Private First Class 34 Rep 184 Posts Drives: 2017 BMW 330e Plugin Hybrid Join Date: Aug 2019 Location: Ireland iTrader: (0)	New belt tensioner is on. Also, the belt was original BMW, seems like it was the original, never changed. Brand new contitech is on. Attached Images __________________ Current: 2017 F30 330e PHEV Past: 2007 BMW E93 N53 Convertible
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12-10-2022, 05:22 PM	#13
mainbearing Lieutenant Colonel 1082 Rep 1,676 Posts Drives: BMW 328i Join Date: Apr 2019 Location: LA iTrader: (0)	Had a belt walked 1/3 off the pulley problem this weekend. Turned out to be a failing mounting bolt. The AL9 aluminum bolt was not strong enough. Makes me wonder how much of the problem was the bolt failing and not the assembly's fault. My post here: https://www.e90post.com/forums/showthread.php?t=1976331 And pics: Failing bolt on top, against a new bolt below:
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12-10-2022, 09:52 PM	#14
mgmavant Enlisted Member 17 Rep 31 Posts Drives: 2008 328xi, 2023 X5M50 Join Date: May 2019 Location: Bethesda, MD iTrader: (0)	I wonder if that bolt was reused from a previous tensioner replacement. Those bolts need to be changed once they are torqued down to the proper torque. At any rate, good thing you caught it before it failed!
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12-10-2022, 10:38 PM	#15
mainbearing Lieutenant Colonel 1082 Rep 1,676 Posts Drives: BMW 328i Join Date: Apr 2019 Location: LA iTrader: (0)	Yeah, if this engine ate the serpentine belt I will just dump it for an Audi anyway. This failed bolt was a new one that came with the INA tensioner, so it was used only once and torqued-angled to spec (18 lb/ft+90deg). Maybe the supplied bolt is of defective metallurgy. Anyway the newest bolt that went in today is a Rein. I used 17lb/ft+80deg this time. LOL. Time will tell.
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12-11-2022, 12:50 PM	#19
mainbearing Lieutenant Colonel 1082 Rep 1,676 Posts Drives: BMW 328i Join Date: Apr 2019 Location: LA iTrader: (0)	I did not use any lube or motor oil on the threads. But given the number of so-called "tensioner failures", I wonder how many of those were actually bolt failures. Wish I kept the original tensioner, because I did not see anything wrong with it when compared to the new one. But I just changed it anyway. These tensioner bolts are not the only problems, engine mount bracket bolts (4 on each side) are known to snap (Rein sells a set of bolts to address those). And cylinder head bolts too. It may just be BMW's poor choice of bolt sizes and metallurgy. This engine was the first to use the stupid magnesium composite casting that saved 22 lbs. And maybe the last? LOL Magnesium weakened the block that N54 did not use it. And engines with turbos is the way manufacturers are moving. Hopefully this magnesium joke is the last from any manufacturer. But in the mean time, yes reduced torque just a bit.
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