Belt Tensioner Torque Specs

Hi guys,

I searched and couldn't find any info, but can anyone tell me what the torque specs are for the belt tensioners? Specifically bolts 1 and 2 in the pic.

Thanks!

I’m pretty sure those are 13mm M10 bolts which are torqued to 42 Nm.

Pig Farmer wrote

I’m pretty sure those are 13mm M10 bolts which are torqued to 42 Nm.

Thank you!

I noticed bolt 2 in your picture came completely loose when i changed my belt last week. It made the whole assembly moving, however when re-tightening to proper torque, I can't move my tensionner anymore pushing with a ratchet on bolt 3. Is that normal ?

Just to avoid the over-torquing of tensioner bolts 1 and 2 and possibly damaging the block, they are silver zinc (ZNS) M8 8.8, not M10. The torque spec for M8 8.8 ZNS is 19NM per TIS:

[edit] I was installing this tensioner today and noticed that bolt #1 was M8 10.9, not 8.8. Bolt #2 is M8 8.8. I used the 8.8 spec for for both (19Nm)

https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/00-maintenance-general-note/00-03-tightening-specifications/5gDQK89

The bolt for the power steering & A/C deflection pulley is an M10 and requires special torque as specified in TIS:

https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/11-engine/11-28-drive-belt-with-tensioning-deflecting-element/5yhnA2X

Does anyone know the torque value of #3? Just wanting to replace the pulley itself and not the entire assembly.

LKN624 wrote

Does anyone know the torque value of #3? Just wanting to replace the pulley itself and not the entire assembly.

Did you find a source for just the pulley? I didn't think it was available separately (from BMW) per the parts diagram.

frankc wrote

Did you find a source for just the pulley? I didn't think it was available separately (from BMW) per the parts diagram.

Yes I did actually. Its made by INA which is the original supplier of the BMW branded one.

Part number is: INA 532 0342 10

Its about 10 euros for one and you'll need two of them. Comes with a new dust cover and the bolt/washer.

Bump anyone know? Thanks!

LKN624 wrote

Does anyone know the torque value of #3? Just wanting to replace the pulley itself and not the entire assembly.

The bolt has a 10mm thread, so 42Nm (31ft lbs) seems like the way to go.
Additionally, it appears the factory used red Loctite on the threads as well, at least that's what appeared to be on my bolt once I got it removed. Had to use a wrench all the way out.

Davisca455 wrote

The bolt has a 10mm thread, so 42Nm (31ft lbs) seems like the way to go.
Additionally, it appears the factory used red Loctite on the threads as well, at least that's what appeared to be on my bolt once I got it removed. Had to use a wrench all the way out.

Thanks for the research but it seems as though...that 40Nm (I just guessed), might be too tight. I am getting a HORRIBLE vibration from the engine which I can feel through the entire car at idle and also when you rev the engine up. Perhaps it might be less?

LKN624 wrote

Thanks for the research but it seems as though...that 40Nm (I just guessed), might be too tight. I am getting a HORRIBLE vibration from the engine which I can feel through the entire car at idle and also when you rev the engine up. Perhaps it might be less?

The only thing touching the inner race of the bearing is the machined shoulder of the aluminum arm and the head of the bolt.
And the inner race of the bearing looks to be a pretty substantial hardened steel single piece unit?
I hope that isn't so much torque that it could cause the pulley to start seizing its bearing.

Davisca455 wrote

The only thing touching the inner race of the bearing is the machined shoulder of the aluminum arm and the head of the bolt.
And the inner race of the bearing looks to be a pretty substantial hardened steel single piece unit?
I hope that isn't so much torque that it could cause the pulley to start seizing its bearing.

Yeah for sure...is there a certain direction the pulley should be facing? Or is it the same on both sides?

Actually looking at NEWtis Torque chart. Its an M10 bolt 10.9 silver coated which it says 56 Nm...so perhaps i'll need to tighten it more.

LKN624 wrote

Davisca455 wrote

The only thing touching the inner race of the bearing is the machined shoulder of the aluminum arm and the head of the bolt.
And the inner race of the bearing looks to be a pretty substantial hardened steel single piece unit?
I hope that isn't so much torque that it could cause the pulley to start seizing its bearing.

Yeah for sure...is there a certain direction the pulley should be facing? Or is it the same on both sides?

My original pulley is symmetrical.

Davisca455 wrote

My original pulley is symmetrical.

Yeah that is what I thought...I might throw the old pulleys back and see if my new ones are defective.

Davisca455 wrote

The bolt has a 10mm thread, so 42Nm (31ft lbs) seems like the way to go.
Additionally, it appears the factory used red Loctite on the threads as well, at least that's what appeared to be on my bolt once I got it removed. Had to use a wrench all the way out.

I had this bolt break on my tensioner, do you know if the thread is 10-32, 10-24 or 10x1.5?

MikeYQM wrote

Davisca455 wrote

The bolt has a 10mm thread, so 42Nm (31ft lbs) seems like the way to go.
Additionally, it appears the factory used red Loctite on the threads as well, at least that's what appeared to be on my bolt once I got it removed. Had to use a wrench all the way out.

I had this bolt break on my tensioner, do you know if the thread is 10-32, 10-24 or 10x1.5?

I'm 99.9% positive it's M10x1.5, but I didn't actually put a thread gauge on the threads to check the pitch.
I do have my hands and eyes on coarse thread M10s on a near daily basis and it did look like a coarse thread bolt to me, which is what I would expect for threading into aluminum.
I do know that the threads on the long bolt used for the fixed idler is M10x1.5 (because I replaced it with a stud), and that one screws into aluminum as well.
Plus, I doubt the BMW engineers would use different M10 thread pitch fasteners into aluminum.

The bolt head has a unique shape though, so let us know where you source a new one.

Davisca455 wrote

MikeYQM wrote

Davisca455 wrote

The bolt has a 10mm thread, so 42Nm (31ft lbs) seems like the way to go.
Additionally, it appears the factory used red Loctite on the threads as well, at least that's what appeared to be on my bolt once I got it removed. Had to use a wrench all the way out.

I had this bolt break on my tensioner, do you know if the thread is 10-32, 10-24 or 10x1.5?

I'm 99.9% positive it's M10x1.5, but I didn't actually put a thread gauge on the threads to check the pitch.
I do have my hands and eyes on coarse thread M10s on a near daily basis and it did look like a coarse thread bolt to me, which is what I would expect for threading into aluminum.
I do know that the threads on the long bolt used for the fixed idler is M10x1.5 (because I replaced it with a stud), and that one screws into aluminum as well.
Plus, I doubt the BMW engineers would use different M10 thread pitch fasteners into aluminum.

The bolt head has a unique shape though, so let us know where you source a new one.

Ouff, I don't even know where to start looking for the bolt. I'm buying a pulley that comes with a bolt and I hope it's the right one.

@MikeYQM
I bought this 70mm OD pulley from FCP
https://www.fcpeuro.com/products/bmw-drive-belt-idler-assembly-x5-545i-645ci-745i-745li-11281440237
and the pulley itself was correct.
It came with a bolt, but the bolt takes a Torx head, which might not be ideal for getting a wrench onto it when servicing the belt?
Junkyard might be the way to go for the bolt?

Side note:
My A/C & PS pulley was slightly smaller (65mm OD) than the Alternator/Water Pump pulley (70mm OD). The 70mm OD did work for both locations though.
I did finally find the proper part number for the smaller pulley, but it doesn't come with a bolt.
https://www.fcpeuro.com/products/clone-porsche-drive-belt-idler-pulley-cayenne-por-95510211921

Dust Cap:
https://www.fcpeuro.com/products/bmw-a-c-idler-pulley-dust-cap-11287535867

can anyone tell me the torque specs for the deflection pulley with the offset hole?

Pig Farmer wrote

I’m pretty sure those are 13mm M10 bolts which are torqued to 42 Nm.

frankc wrote

Just to avoid the over-torquing of tensioner bolts 1 and 2 and possibly damaging the block, they are silver zinc (ZNS) M8 8.8, not M10. The torque spec for M8 8.8 ZNS is 19NM per TIS:

[edit] I was installing this tensioner today and noticed that bolt #1 was M8 10.9, not 8.8. Bolt #2 is M8 8.8. I used the 8.8 spec for for both (19Nm)

https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/00-maintenance-general-note/00-03-tightening-specifications/5gDQK89

The bolt for the power steering & A/C deflection pulley is an M10 and requires special torque as specified in TIS:

https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/11-engine/11-28-drive-belt-with-tensioning-deflecting-element/5yhnA2X

Bumping an old thread but I will be replacing my belt tensioner assembly (part no. 11287838194) and drive belt tensioner (part no. 11287841546) tomorrow, and if I understand all the info above the correct torque values for each bolt are:

Bolt 1: M8 10.9 - 42Nm
Bolt 2: M8 8.8 - 19Nm

Just wanting to confirm in case anything has changed or different info has become available in the past few years as google seems to give me the torque values below:

M8 10.9 - 34 Nm
M8 8.8 - 24 Nm

Theodore wrote

For those times when you just want the damn torque spec! Click the underlined links for additional DIY help.
Belt Tensioner Machine Screws (machine screws on either side of belt tensioners, both belt tensioners) - 40NM (30 ft lb) Note: BMW TIS for E9X M3 does not specifically speak to the torque requirement for this machine screw, refer to generic BMW standard for M8 course thread 10.9 strength bolts/machine screws to get this torque

https://www.m3post.com/forums/showthread.php?p=25189924

And this thread is giving me a value of 40Nm