Hey everyone, I am replacing the guide pulleys, belt tensioner and belt on my 2014 E550 4MATIC Sedan.

I am trying to find the correct torque values for:
2: ____NM (I believe it's 20NM for the tensioner bolts?)
4b: ____ NM
6: ____NM
7: ____NM
8:____NM



Also, any tips of things to avoid would be appreciated.

Links to parts I purchased:
Location 2: Drive Belt Tensioner + Pulley
Location 4b: Drive Belt Idler Pulley
Location 6: Idler Pulley
Location 7: Idler Pulley
Location 8: Idler Pulley
Drive Belt (compatible for the M278)


Thanks!

Its weird the doc with this info doesn't also give the min torque settings on the bolts for each pulley?? Very Un-German!!

I found this document with some slightly different numbering.

So then using my original location identifiers:
2: 20 NM
4b: 70 NM
6: 35 NM
7: 35 NM
8: 35 NM

Something is 70 NM but I'm not sure. I feel 70 NM is pretty high for one of the guide pulleys.

Thoughts anyone?

I just did this job tonight and I believe you may be incorrect. I'm not totally sure but here is what I went with:
2: 20 NM
4b: 35 NM
6: 35 NM
7: 35 NM
8: 70 NM

I believe guild pulley 8 gets 70NM due to step 11 in the attached document. That is the step where it mentions "guide pulleys (3)" and also mentions "BA13.25-P-1002-01Y" which is listed on the 2nd page with 70NM. If we assume its one of the 3 and then you look at them, you will see 1 of them has a much bigger bolt and is twice as heavy as the other 2 pulleys, so that the one I went with at 70NM. Once tightened at 70 NM it still spun freely, so seems to be fine.

Also, another reason I believe it's not the upper guide pulley at 70NM is that is mentioned in steps 11-15 where it is referenced to "BA13.25-P-1005-01Y" which is listed on the 2nd page with 35NM.

Additionally, yes, I am fairly certain tensioner bolts are 20 NM: "BA13.25-P-1001-01Y - poly-V belt tensioning device - 20NM"

One other thing, don't let "BA13.25-P-1003-01Y" confuse you, it got me for a few min, but it is only bolts for the "guide pulley CARRIER" being mentioned, NOT actual guide pulley bolts. There is no guide pulley getting set to 20 NM. As far as I can tell this is the bolts for the bracket in step 11, since they are small bolts and 20NM makes sense for these.

Id like to bump this thread for confirmation on the torque numbers for anyone who has done this job. Unfortunately op and the other poster have not been online for quite some time

Replying here to confirm everything is still attached and I've had no problems. Hope that helps.

Pulley No3 goes bad faster than No2 due to wobbly compressor misguiding the belt sideways and the head super heating the bearing grease in liquid form. It leaks right out of genuine bearing seal.

No need to scratch head with standard maintenance... new serpentine kit every 65kMi.

Yes, 65k Mi is the way to go, I am approaching 110K. It is always the first time got me really nervous: what parts, what torque, what would I miss.

Just realized that I posted to the wrong forum. Moved to W166. Thanks!

the torque is related to a steel screw in an aluminum head... nothing yields!

This assembly can hardly get tightened without stripping the engine-side threads.

Use blue Loctite or else...