DIY: idler pulley replacement

[DontTellMyWife]

I did the work tonight and can confirm the INA part above was OE on the tensioner arms. Had to use the exiting bolt as the one that comes with it are different.

[Davisca455]

I removed both tensioner pulleys and the deflection pulley.
All three pulleys were a different diameter.

A/C and PS Belt Tension Roller
65mm OD x 17mm ID x 26mm Wide (14mm bearing width)
Number found on pulley: F-553814.03-0300

Alternator Belt Tension Roller
70mm OD x 17mm ID x 26mm Wide (14mm bearing width)
Number found on pulley: F-233151.06

A/C and PS Belt Fixed Idler
80mm OD x 10mm ID x 26mm Wide
3 numbers found on pulley: BMW 1128 7841531-01 and 1087790120FR and INA F-564969

The A/C and PS (65mm) tension pulley was difficult to find though. Only place I could find it was eBay Europe.
So I just installed a 70mm pulley instead. The belt was noticeably more difficult to install, but it seems to work fine.

Oh ya, the new pulleys fixed this annoying groaning sound coming from the A/C and PS belt circuit.

[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):
[COLOR="Red"]Global Part #: 5320557100[/COLOR]
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):
[COLOR="red"]Global Part #: 5320342100[/COLOR]
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:
[COLOR="red"]Global Part #: 5320418100[/COLOR]
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

[Davisca455]

The above post has all three pulley, and dust cap part numbers, for my later '08 M3 (center hole fixed idler).
I also added the part numbers for the offset hole fixed idler and its dust cap at the bottom of the list.

I bought all three dust cap sizes (even though we only need two), because FCP's descriptions aren't clear...and they're inexpensive.
So I have an extra dust cap for an offset hole fixed idler (Right side of picture).
If anyone wants it, PM me and I'll drop it in the mail.

[Assimilator1]

Wish I'd found this thread before I did the job, would have saved me quite some time! lol

My car's build date is 4/2008, I don't recall the build day [edit, belt type is single sided], but the 2 idler pulleys were the same size (IIRC), and now one is slightly smaller. After some fretting I just installed them to see how it did (didn't know if the old or new pulleys were wrong), I figured the slightly smaller pulley (~4mm) would end up running slightly faster and very slightly reduce belt tension (the tensioner would have to move slightly further out).
Well the tension isn't an issue as the belt doesn't slip, I suppose the slightly higher speed of the pulley will wear it out a bit earlier.

I'll have to find out and note which type my engine is and note the right pulleys for next time!
Thanks for the info Davisca455 and co

[Califurnia]

Originally Posted by Assimilator1

Wish I'd found this thread before I did the job, would have saved me quite some time! lol

My car's build date is 4/2008, don't recall day or belt type (might have been single sided), but the 2 idler pulleys were the same size (IIRC), and now one is slightly smaller. After some fretting I just installed them to see how it did (didn't know if the old or new pulleys were wrong), I figured the slightly smaller pulley (~4mm) would end up running slightly faster and very slightly reduce belt tension (the tensioner would have to move slightly further out). Well the tension isn't an issue as the belt doesn't slip, I suppose the slightly higher speed of the pulley will wear it out earlier.
I'll have to find out and note which type my engine is and note the right pulleys for next time!

Thanks for the info Davisca455 and co

I have a 6/2008. Is the idler pulley one sided? There's not much difference on each side and didn't check which side it was originally on. Also what are the torque specs for the water pump to housing, water pump pulley bolts?

[Assimilator1]

Your idler pulley question doesn't make sense I'm afraid . The belt is either single or double sided (multi v's on one or both sides), not the pulleys.
Did you mean the pulley size?
No idea on torque specs btw.

[Kiefermeister]

Should look like this if it's the early production offset pulley. And there's plenty of difference as the engine side has a metal extension. Once you have the pulley lined up, it only goes in one way.

[Assimilator1]

I forgot about the offset thing, curiously (for an 4/2008 build) mine doesn't have it IIRC (still need to take a look), guess it must have been built right at the end of the month!
Looking at bimmer.work, turns out mine has a build date of 17/4/08, so I'm even more confused now! lol

[MisterClutch888]

just installed my Macht Schnell pulley kit. my build is Feb 2008. So i can confirm that the idler pulley bolt is "off-center" and the belt routing is definitely "over" the power steering pump.

[Califurnia]

Originally Posted by Assimilator1

Your idler pulley question doesn't make sense I'm afraid . The belt is either single or double sided (multi v's on one or both sides), not the pulleys.
Did you mean the pulley size?
No idea on torque specs btw.

I meant the actual idler pulley not the belt. I didn't know if it mattered what side I put the pulley in (the round thing with the bearings inside it that spins). I ended up putting everything together and the engine works. I figured it out I guess. Thanks

[SuckaFree]

Originally Posted by jfirwin

This DIY really helped.

My M3 was built in Feb 02, so I made sure I had the right idler pulley. (Thanks, Theodore!)

While I was at it, I also replaced:

the accessory belt
the accessory belt tensioner
the accessory belt pulley
the A/C Belt
the A/C belt pulley
and the A/C belt Tensioner

ECS tuning part #2777259

BTW, you can get away with not replacing these, (except the belts) when you start hearing that squealing from under the hood (mine started around 85K miles) it'll be the idler pulley. I've always believed that you should replace parts that'll liable to go bad while you are at it. The pulleys all run on bearings, so they will wear out at some point.

I couldn't get the accessory (alternator) belt off without removing the idler pulley. Perhaps someone knows a better way?

The tensioners and pulleys are 14mm bolts, less the idler pulley.

Those bolts are not on super tight, so make sure you don't wrench them down too tight.

Remember there are rubber bushings that can be crushed.

Be super careful of the radiator overflow hose. The nipple on the upper radiator breaks easily.

The hardest part to removing the fan housing is getting it past the upper radiator hose. Be patient, be careful, and you can get the housing out without breaking anything. (I didn't)

+1 for removing the underbelly cover. Not only does it make it easier to reattach those lower hoses, but also to retrieve those dropped parts/tools.



edit - Just noticed that the picture below is wrong. The A/C / Power Steering Belt goes OVER the Power Steering pulley (#3), not under. It also goes UNDER the Idler pulley (#5), not over. See the pic below.

edit edit - So, ECS sent me the wrong belts. The correct belts for my pre-May 2008 are 6PK1067 and 6PK1460



Hey! It's about time I ask questions here, instead of going to dealers and others.
Have tried to change the belt on my power steering like 2-3 times now, every time I get the wrong belt. So was reading up on this thread and was convinced I had a pre-may build, but I'm starting to doubt it now.

It looks like my power steering belt goes like that picture, with ribs on both sides.. so it's pulling the power steering with the outside of the belt.
2 times the length was completely off, the last time the length was fine.. but the mechanic said that power steering didn't work with it.

Do I need a belt with ribs on both sides? And which one is it? Please help! Haha

[Mdriv3r]

Originally Posted by SuckaFree

Hey! It's about time I ask questions here, instead of going to dealers and others.
Have tried to change the belt on my power steering like 2-3 times now, every time I get the wrong belt. So was reading up on this thread and was convinced I had a pre-may build, but I'm starting to doubt it now.

It looks like my power steering belt goes like that picture, with ribs on both sides.. so it's pulling the power steering with the outside of the belt.
2 times the length was completely off, the last time the length was fine.. but the mechanic said that power steering didn't work with it.

Do I need a belt with ribs on both sides? And which one is it? Please help! Haha

The engine pic shows a early 2008 build. The colored diagram (red and blue) shows a after early 2008 build.

On the older style. The belt is one sided and goes under the deflection (idler puller) and over the power steering pump pulley. The idler pulley also has an offcenter bolt hole, several images are in this thread of that.

On the newer style, the belt is two sided and will route over the deflection pulley (idler pulley) and under the powersteering pulley, hence two-sides belt.

Take the cap off of your idler pulley, and check if it has an offcenter hole. Check the build date as well. Study the diagrams and you should be able to tell what you have.

[Mdriv3r]

To help you. Take off the cap the right of your power steering pulley. That is your idler pulley (note yellow arrow in picture pointing to idler puller cap). This can be done with a flat head screw driver.

If the bolt is off centered like in the second pic, I attached, then you definitely would have an early 08 build and would need the one sided belt. It would be routed as seen in the engine pic from my earlier post.

[Mdriv3r]

Last thing, just call the dealer and give them your vin. Ask for the AC belt part number. That will make sure, by build date that you get the right belt. Then show you mechanic the diagrams. This can be confusing for people who arent familar with this platform.

Oh yeah, since you took the time to learn this. I suggest supercharging good luck!

[SuckaFree]

Thanks! But with my vin-number I get the wrong belt. Found a number on the AC belt, 6PK1425 tho.. so changed that one. BMW offered to try it again, with the same belt that failed, for $400. Hell no.
According to my pic the belt goes below the power steering tho? Tried using a belt with ribs on one side, and the power steering didn't work.
Can't find belts here with ribs on both sides tho! That's why I had to ask here

[SuckaFree]

Do you guys have a number for that double ribbed belt?

[Mdriv3r]

Link AC dual sided belt:

https://www.fcpeuro.com/products/bmw...m3-11287841529

Here is the belt at fcpeuro. They are a good source. Ecs tuning is good too.

AC Belt Dual sided
BMW OEM part number: 11287841529

OE from Continental: 6DK1100

I suggest the Continental belt, its cheaper.

You may wanna do the accessory belt to if you havent.

Link Accessory belt: (same all years, for alternator, water pump etc...)

https://www.ecstuning.com/b-continen...1287837898~ct/


Accesory belt

OEM part number: 11287837898
Continental OE part number: 6PK1460

I suggest Continental for both. You'll spend <$40 for the two. FCPEuro is sold out of accessory belts right now, but ECS tuning has both.

[Mdriv3r]

Also, if you attempt a diy... Be very careful when pulling the fan. If you break it, its a $1000 to replace.

You can search the forum for diys on that. Also, macht schnell has a good guide on most of it for their pulley kit.

Link Macht Schnell vid:

[SuckaFree]

Thanks! Found it after lots of googling. It's impossible to find it here in sweden, everyone say they don't make that doubled side belt.
Will order one right away.

[Mdriv3r]

Originally Posted by SuckaFree

Thanks! Found it after lots of googling. It's impossible to find it here in sweden, everyone say they don't make that doubled side belt.
Will order one right away.

Ah, I see. Glad you got that sorted.

[Harryc9]

nice post, doing my belts this weekend, car is more than 8.5 years old so seems a good idea. also replacing the pulleys at the same time and doing the thermostat (coolant change) too.