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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 12-14-2013, 04:12 AM
MJVV MJVV is offline
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Belt tensioners

Hi All,
Daughter's 2002 325i threw the main belt yesterday, literally shredded and wrapped around fan clutch. Question is regarding the tensioner pulley. I see many reports that these cars are notorious for failing tensioners. If it seems to spin freely, is it still recommended to replace simply because the belt failed, or can I assume the squeaking and belt failure were nothing to do with the tensioner(as long as it seems to spin freely by hand). No idea how long the tensioners have been in there. Thanks!
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Old 12-14-2013, 04:52 AM
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ahull ahull is offline
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Spinning freely means the grease is almost gone. New ones will spin with resistance almost not spinning. There's also the idler pulley. Usually they'll squawk or chirp a little on cold starts when they're near total failure. You may have some damage from the belt. Fan blades shroud hoses and expansion tank etc.

A good life for pulleys is 60-80k miles. If you see lots of little cracks in the underside of the belts then they're ready. A few cracks here n there is ok. 80k miles is good life for belts.
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DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
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Last edited by ahull; 12-14-2013 at 04:55 AM.
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  #3  
Old 12-14-2013, 06:33 AM
MJVV MJVV is offline
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Quote:
Originally Posted by ahull View Post
Spinning freely means the grease is almost gone. New ones will spin with resistance almost not spinning. There's also the idler pulley. Usually they'll squawk or chirp a little on cold starts when they're near total failure. You may have some damage from the belt. Fan blades shroud hoses and expansion tank etc.

A good life for pulleys is 60-80k miles. If you see lots of little cracks in the underside of the belts then they're ready. A few cracks here n there is ok. 80k miles is good life for belts.
THANKS! I'll do a good look over once I get the shroud and fan out of the way, will pick up a new tensioner as well. Appreciate the response.
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Old 12-14-2013, 06:47 AM
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ahull ahull is offline
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Originally Posted by MJVV View Post
THANKS! I'll do a good look over once I get the shroud and fan out of the way, will pick up a new tensioner as well. Appreciate the response.
You can get just the pulleys themselves for less if the tensioner mechanism appears to be ok. Check the wiki near the top of the page:
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2003 330i TiAg Sport Pkg
DIY MODS: AA Stage I supercharger, Meyle HD FCAs w Powerflex CABs, Bilstein shocks, Meyle HD Rtabs, Angel Eyes, Clear Corners/Markers w/ LEDs, LED tails, ZHP rims, Akebono pads, AUX input
DIY E46 Merit Badges: Sunroof resurrection, CCV, OFHG, VCG w/ VANOS seals, DISA, Cooling Refresh I, steering giubo, window regs, Magnetic Infandibulator (see wiki)
DIY On deck: Rear Diff bushing. UUC SSK, clutch job eventually, Wavetrac LSD
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Old 12-14-2013, 08:02 AM
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SJBimmer SJBimmer is offline
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If tensioner is mechanical, I suggest converting to hydraulic. More expensive for sure, but the mechanical is no longer available from BMW directly from what I have been told. There must be a reason for this if is in fact true. When I had a tensioner problem under my CPO warranty, they installed a new hydraulic tensioner. It also supposedly has a more robust mounting system utilizing 3 bolts instead of 2 if my memory serves me correctly. Mine was done back in 2007, and I researched it all at that time. Detail are a little hazy, and I'm sure someone will correct me if my statements are incorrect. Good luck!
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Old 12-14-2013, 08:54 AM
cvx5832 cvx5832 is online now
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The hydraulic tensioner is nice, but I haven't seen evidence that they were indeed "better". Lots of us with mechanical tensioners (albeit with replaced pulleys) have 100k+ even 200k+ miles. There was a thread on E46F for that specifically some time ago and most stayed with the mechanical setup unless BMW paid for it.

SJ is right in that the mechanical (11281427252) can't be bought from BMW anymore. Even the online OE BMW sellers won't sell it. But they're still dime a dozen at all the OEM retailers like autohausaz and rmeuropean. The pulleys alone can be had just about anywhere.
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Old 12-14-2013, 09:30 AM
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SJBimmer SJBimmer is offline
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Quote:
Originally Posted by cvx5832 View Post
The hydraulic tensioner is nice, but I haven't seen evidence that they were indeed "better". Lots of us with mechanical tensioners (albeit with replaced pulleys) have 100k+ even 200k+ miles. There was a thread on E46F for that specifically some time ago and most stayed with the mechanical setup unless BMW paid for it.

SJ is right in that the mechanical (11281427252) can't be bought from BMW anymore. Even the online OE BMW sellers won't sell it. But they're still dime a dozen at all the OEM retailers like autohausaz and rmeuropean. The pulleys alone can be had just about anywhere.
I believe they were considered better because of a more robust mounting system than the mechanical. May have an effect at sustained autobahn speeds, which BMW must take into consideration, but most in this country will probably never see an advantage. I would think they would last longer though. My mechanical failed at about 35K. This is an unacceptable service life in my opinion. It is true that cost always plays a part in a replacement. I like to take the long view in any parts critical area, as far as what would happen if that part failed? That's just me though. When i was young and trying to afford school while working nights, I made some of the worst half a$$ed repairs on my car imaginable.
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