DIY: idler pulley replacement

[krayzie]

Just a FYI for anybody doing this
The pre May 08 M3 also has a few other differences besides the offset idler pulley.
AC belt is shorter and originally uses a 1067 belt
Both tensioner pulleys are the same at 70mm

Just wondering for anybody that has ordered 70mm pulley listed......
How did you disassemble the pulley from the round backplate and torx bolt since they seemed press fitted together?
Did anyone reuse the round backplate with the original bolt or just toss it?

[Davisca455]

Originally Posted by krayzie

Just a FYI for anybody doing this
The pre May 08 M3 also has a few other differences besides the offset idler pulley.
AC belt is shorter and originally uses a 1067 belt
Both tensioner pulleys are the same at 70mm

Just wondering for anybody that has ordered 70mm pulley listed......
How did you disassemble the pulley from the round backplate and torx bolt since they seemed press fitted together?
Did anyone reuse the round backplate with the original bolt or just toss it?

Not 100% sure, but I have a vague memory of grabbing the aluminum (?) backing plate with a vice or channel lock pliers and unscrewing the bolt?
Am I remembering a little crimp feature that needs to be defeated?
I know I got it apart though and trash canned the supplied Torx bolt and the backing plate.

I reused the original shoulder bolt.

[Assimilator1]

Unscrewing a bolt from a crimped washer, rings a bell here too.

[krayzie]

Thanks
Eventually got it off by using a vice and breaking the metal retaining tabs on the backplate.

Everything back together but never realized how super close the idler pulley is to the water pump pulley. Seems like 1mm between the two and would cause rubbing issues if they were skewed.
That's probably why my idler pulley melted and the belt snapped after the bearings seized.... luckily no damage to any other parts.

Another FYI
The new supplied torx bolts will not fit as previously mentioned because they are too long but have the right pitch and thread so could be used if cut shorter.

The supplied plastic cap covers will also not fit the original bolts as the bolt heads are taller than the torx bolts so you will need to order new caps if you lost them

[Davisca455]

Originally Posted by krayzie

Thanks
Eventually got it off by using a vice and breaking the metal retaining tabs on the backplate.

Everything back together but never realized how super close the idler pulley is to the water pump pulley. Seems like 1mm between the two and would cause rubbing issues if they were skewed.
That's probably why my idler pulley melted and the belt snapped after the bearings seized.... luckily no damage to any other parts.

Another FYI
The new supplied torx bolts will not fit as previously mentioned because they are too long but have the right pitch and thread so could be used if cut shorter.

The supplied plastic cap covers will also not fit the original bolts as the bolt heads are taller than the torx bolts so you will need to order new caps if you lost them

That is correct, the supplied bolt and cap can be discarded.

Rollers and cap part numbers can be found here…

https://www.bimmerpost.com/forums/sh...php?p=26791901

[Assimilator1]

Has anyone noticed that the offset idler pulley has been superseded by the ctr hole idler?! See here - https://www.realoem.com/bmw/enUS/sho...diagId=11_4120
Err, so the offset isn't needed anymore??

And anyone know what size the AC tensioner pulley should be for the earlier version?

[suk610e92]

Originally Posted by Sean05

If your car sounds like this its your idler pulley

YELLOW ARROW IDLER PULLEY 16mm bolt to remove the Pulley
RED ARROW TENSIONER 14MM BOLT and push down to remove the tension so you can remove the belt.


STEP 1: remove the intake


STEP 2: remove the radiator fan only one screw on the fan upper left if your facing your engine then slightly pull the fan. Make sure to unplugged the fan and move any thing thats blocking the way the only tough part is to move the radiator hose just slowly pull it out again move anything thats blocking and u dont have to take anything off

STEP 3: take the cover off the pulley tentioner and get a 14mm socket and push down. It will move the tensioner so u can remove the belt... This is not the idler pulley its the one on top of that pulley


STEP 4: 16mm socket to remove the idler tensioner and replace


STEP 5: put everything back and done

Would have taken 30 minutes but i took my time

You're a life saver my car was making this exact noise. Tried to search forums and couldn't find anything on it. Searched idler pulley and your post came up, I replaced the pulley and no more noise

[chutak]

Originally Posted by Davisca455

I talked with my industrial bearing guy, Dale, at Motion Industries.
He contacted his counterpart on the Automotive side and they think they found the part number for the 65mm pulley that was on my A/C & PS Tensioner. It's listed as a Porsche part though, so....I'll get one, see if it fits and edit the post when it gets here.

*Edit: The 65mm "Porsche" pulley is the correct part for my car, same exact part number.

A/C & PS Tensioner Pulley (65mm OD):
Global Part #: 5320557100
https://www.fcpeuro.com/products/clo...or-95510211921

https://www.autohausaz.com/pn/IN-95510211921

Plastic Dust Cap:
https://www.fcpeuro.com/products/bmw...er-11287835996



Alternator & Water Pump Tensioner Pulley (70mm OD):
Global Part #: 5320342100
OEM:
https://www.fcpeuro.com/products/bmw...li-11281440237

OEM:
https://www.autohausaz.com/pn/11281440237

Plastic Dust Cap:
https://www.fcpeuro.com/products/bmw...er-11287835996

Excellent post! Just ordered the tensioner pulleys to replace while I'm in there replacing belts. Pretty substantial savings compared to purchasing each of the tensioner assemblies at $150+ each!

For those who've replaced the tensioner pulleys mentioned, what torque spec did you use for the center bolt? I figure I'd use the same as the idler (deflection) pulley, which is 15nm + 70 degrees turn. Does that sound right?

[Davisca455]

Originally Posted by chutak

Excellent post! Just ordered just the tensioner pulleys to replace while I'm in there replacing belts. Pretty substantial savings compared to purchasing each of the tensioner assemblies at $150+ each!

For those who've replaced the tensioner pulleys mentioned, what torque spec did you use for the center bolt? I figure I'd use the same as the idler (deflection) pulley, which is 15nm + 70 degrees turn. Does that sound right?

It's a 10mm coarse thread bolt, so 30ft lbs is what I torqued it to.

Factory install had red thread locker on it, so I cleaned the thread locking compound from threads of the bolt and the threads of the tapped hole, cleaned the bolt and tapped hole with alcohol, added Loctite 271 (red) and torqued to 30ft lbs.

[chutak]

Originally Posted by Davisca455

It's a 10mm coarse thread bolt, so 30ft lbs is what I torqued it to.

Factory install had red thread locker on it, so I cleaned the thread locking compound from threads of the bolt and the threads of the tapped hole, cleaned the bolt and tapped hole with alcohol, added Loctite 271 (red) and torqued to 30ft lbs.

Thank you very much! 30 ft-lbs is the same as the idler pulley w/offset hole, so that makes sense. I will do the same. Think I already have some blue thread locker, so I'll probably use that.

[RocketyMan]

*SUBSCRIBED*
Anyone interested, I am ordering the Continental Elite Poly V belt in addition to the pulleys. These belts have the "gatorback" cutouts so that the belts themselves are even more quiet via acoustic-cancelation.


Waterpump & Alternator:
CONTINENTAL ELITE 4060575

A/C & PS Pump: (clockwise pre-May 2008)
Continental Elite 4060420

[cheezeit]

Originally Posted by Davisca455

I talked with my industrial bearing guy, Dale, at Motion Industries.
He contacted his counterpart on the Automotive side and they think they found the part number for the 65mm pulley that was on my A/C & PS Tensioner. It's listed as a Porsche part though, so....I'll get one, see if it fits and edit the post when it gets here.

*Edit: The 65mm "Porsche" pulley is the correct part for my car, same exact part number.

A/C & PS Tensioner Pulley (65mm OD):
Global Part #: 5320557100
https://www.fcpeuro.com/products/clo...or-95510211921

https://www.autohausaz.com/pn/IN-95510211921

Plastic Dust Cap:
https://www.fcpeuro.com/products/bmw...er-11287835996



Alternator & Water Pump Tensioner Pulley (70mm OD):
Global Part #: 5320342100
OEM:
https://www.fcpeuro.com/products/bmw...li-11281440237

OEM:
https://www.autohausaz.com/pn/11281440237

Plastic Dust Cap:
https://www.fcpeuro.com/products/bmw...er-11287835996




A/C & PS Fixed Idler/Deflection Pulley (80mm OD) Center Hole:

BMW:
https://www.fcpeuro.com/products/bmw...m3-11287841531
(FCP's website prompted me to ask if I wanted the less expensive (Vaico) option, but it turned out to be the offset version. FCP Euro has a glitch on their side, so be advised.)

BMW:
https://www.autohausaz.com/pn/BM-11287841531

Plastic Dust Cap:
https://www.fcpeuro.com/products/bmw...ap-11287535867


A/C & PS Fixed Idler/Deflection Pulley (80mm OD) Offset Hole:
Global Part #: 5320418100
BMW:
https://www.fcpeuro.com/products/bmw...ey-11287841228

BMW:
https://www.autohausaz.com/pn/11287841228

OEM:
https://www.autohausaz.com/pn/11281738605

Plastic Dust Cap:
https://www.fcpeuro.com/products/bmw...ap-11281730349

For anyone doing this in the future, you can also get the INA version of the centered (05/2008+) 80mm fixed idler pulley. It's $21 instead of $83 for the BMW M3 specific part.

The pulley is the exact same - the only difference is the bolt length. Discard the included bolt and re-use your very long idler bolt. You can use the new sheet metal dust shield, it is the same as the old one.

BMW 11287535860 (for N52 with short bolt)
INA 5320512100 aka 532 0512 10
https://www.fcpeuro.com/products/bmw...60#description

On the 70mm pulley, you can use a pick or small screwdriver to break the crimps (they are weak) on the included cast washer and it will slide / unscrew right off.

Also attached is a pic of my 117K mile belts compared to a new one. No cracks but the grooves are deep. The pulleys that came off my car were also still tight and greased, but replacing them at my mileage seemed like a good idea.

When re-installing the belts, I found it easiest to slide the belt over the smooth pulleys - specifically the tensioner pulley on both the alternator and AC sides. On the AC side you must have the belt already looped over the fixed idler pulley before screwing the idler pulley in or there is not enough space to squeeze the belt in between the pulley and fixed oil line.