M42 Alternator Belt Tensioner Stuck?

[Bairdogg]

The tensioner for the alternator belt on my M42 appears to be stripped. Any way to reduce the tension to remove the belt without cutting it? (I need to get the new belt on anyway, if anything I would assume the tightness of the belt would help ease the tensioner move inwards.) It's a rack and pinion type deal, but the teeth on the rack are completely stripped. I will snap pics when I get home if what I'm saying is unclear (it's early). If anybody knows a workaround it would be appreciated. Thanks, guys.

[Kershaw]

Loosen the nut on the back until the teeth are disengaged. Then use a prybar to move it around. Or large screwdriver. Or your hands if you're really lucky.

[Bairdogg]

Well, no luck with the pry bar (nothing to pry against that gives good leverage). Looks like I'm replacing the rack part. Anybody know what it's called?




Sent from my iPhone using Tapatalk

[Uturn540]

I believe these are the parts you are looking for.

http://www.realoem.com/bmw/enUS/show...diagId=12_0186

[Kershaw]

Looks like you also need a few cans of this



and get a can of this

[Bairdogg]

Those do look like the parts for sure, I couldn't find them on RealOEM for my life so thanks a bunch. Douchebag at the dealership tried to convince me that they weren't however, instead showing me a bracket that looked absolutely nothing like the old one based on my VIN number. Then he tried to tell me that my engine must not be an M42 and that an old owner must have swapped it. Right. Anyway, the only place I can find that bracket is on ECS for almost $90, so it looks like its back to the prybar for now haha

- - - Updated - - -

- - - Updated - - -

Looks like you also need a few cans of this

You certainly aren't wrong... I don't like the thought of getting Brakleen on the already 27-year-old rubber bits that I haven't gotten my lazy ass around to replacing yet. One day I'll get under there and clean off all that crap. Hopefully.

[Uturn540]

Bavarian Autosport is a little cheaper at $77. Or find someone who has a wirefeed welder, file, and Dremel tool and rebuild the bracket and just buy a new nut.

[Kershaw]

I usually just use a pry bar to tension it and then tight down the gear nut. BMWs system sucks. It only works if all the parts are completely free from corrosion and easily spin.

[Bairdogg]

I usually just use a pry bar to tension it and then tight down the gear nut. BMWs system sucks. It only works if all the parts are completely free from corrosion and easily spin.

Could I ask for more details? What are you prying and what nut are you tightening? As far as I can tell the only adjustable part of the alternator system is the tensioner.


Sent from my iPhone using Tapatalk

[Kershaw]

First off, I work on m20s, the system for m42s is different. YMMV. I pry between the block and the alternator, and try my best to pry the alternator away from the block. If I am lucky a friend (or my gf) will hold the pry bar while I tighten the gear nut. You can see in this pic there is space behind the aluminum timing belt cover to pry on. Definitely don't pry on any covers. (The tensioner attaches to the top empty bolt hole)

[Bairdogg]

First off, I work on m20s, the system for m42s is different. YMMV. I pry between the block and the alternator, and try my best to pry the alternator away from the block. If I am lucky a friend (or my gf) will hold the pry bar while I tighten the gear nut. You can see in this pic there is space behind the aluminum timing belt cover to pry on. Definitely don't pry on any covers. (The tensioner attaches to the top empty bolt hole)

Okay I'm going to give it another shot today. Maybe if I pry the alternator towards the block using the drivers side tire as a fulcrum I can make it work. Not sure, I need to take another look. Can't I just begin to remove the alternator, would that lessen the tension on the belt? Only worry about doing it that way would be stripping something trying to tighten the alt. back down while the belts pulling it to the side. I could probably use a pry bar for that.


Sent from my iPhone using Tapatalk

[Kershaw]

It should move easily in both directions. Did you loosen the bottom bolt as well?

[Bairdogg]

I'm a sleep deprived idiot, the alternator belt isn't the problem, it's the power steering (?) belt, all the way at the bottom, furthest one out. I had taken a break after trying for a few days before posting this thread so I apparently forgot which belt was giving me the issue. So that rules out twisting any of the pulleys.

Those are the only two pulleys I have to work with. Hmm.


Sent from my iPhone using Tapatalk

[Bairdogg]

Okay, I was able to get the belt off by bathing the bolts that allow the rotation in PB blaster then using a clamp to squeeze the belt in the middle until it pulled the tensioning pulley in far enough. And of course Pep Boys gave me the wrong belt size even though I told them what size I needed. But they insisted on using their damn computer, and there was no size on the package on the belt they gave me.


Sent from my iPhone using Tapatalk

[RomeoMike]

Hi:

Part numbers for an M42:
Alternator belt 11-23-1-469-235, 10mm x 1025mm
AC belt 64-55-1-469-268, 13mm x 890mm
Power Steering belt 32-42-1-469-238, 10mm x 800mm

Full post on changing the M42 accessory belts (wrote this in December 2010)

https://www.bimmerforums.com/forum/s...5#post20980635

[Bairdogg]

Hi:

Part numbers for an M42:
Alternator belt 11-23-1-469-235, 10mm x 1025mm
AC belt 64-55-1-469-268, 13mm x 890mm
Power Steering belt 32-42-1-469-238, 10mm x 800mm

Full post on changing the M42 accessory belts (wrote this in December 2010)

https://www.bimmerforums.com/forum/s...5#post20980635

Thanks, I returned the belt from pep boys... turns out the dumbass there gave me a belt for a tractor... in my defense there was no indication of that on the packaging or size, and I didn't have the old belt with me for comparison. I grabbed one from the computer and one we eyeballed to be the right size, so if neither of those fit I'm giving up and buying an s54.

In your write up I saw you said to stand the fan up vertically. Any reason for that? I've had mine lying on the ground for about a month now as I didn't want to break the blades by leaning it.


Sent from my iPhone using Tapatalk

[RomeoMike]

Regarding standing up the fan vertically, it's more for the sake of the fan clutch (lessens odds of fluid leaking from it). That was the prevailing wisdom of people with more experience than me.