E-Class (W212) 2010 - 2016: E 350, E 550
Sponsored by:
Sponsored by: CARiD

M278 Pulley & Belt Tensioner Torque

Thread Tools
 
Search this Thread
 
Rate Thread
 
Old Jun 4, 2023 | 09:41 PM
  #1  
claytonncox's Avatar
Thread Starter
Newbie
 
Joined: Jun 2023
Posts: 9
Likes: 4
From: Connecticut
2014 E550 4MATIC Sedan
M278 Pulley & Belt Tensioner Torque

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!
Reply
Old Jun 4, 2023 | 11:26 PM
  #2  
Aussie_E350_Wag's Avatar
Senior Member
5 Year Member
Photoriffic
Liked
Loved
 
Joined: Feb 2021
Posts: 278
Likes: 146
From: Canberra ACT
2013 E350 Facelift (Japan Import) 2007 E350 Elegance Wagon, 2014 E350 Wagon facelift model Jap Model
Its weird the doc with this info doesn't also give the min torque settings on the bolts for each pulley?? Very Un-German!!
Reply
Old Jun 5, 2023 | 07:51 AM
  #3  
claytonncox's Avatar
Thread Starter
Newbie
 
Joined: Jun 2023
Posts: 9
Likes: 4
From: Connecticut
2014 E550 4MATIC Sedan
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?
Attached Files

Last edited by claytonncox; Jun 7, 2023 at 12:57 PM.
Reply
Old Dec 17, 2023 | 10:05 PM
  #4  
ssmiller60's Avatar
Junior Member
 
Joined: Sep 2016
Posts: 17
Likes: 5
2014 E550 coupe
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.
Reply
Old Feb 19, 2025 | 09:38 AM
  #5  
bentz69's Avatar
Super Member
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Oct 2015
Posts: 723
Likes: 115
From: Long Island
'16 CLS63S
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
Reply
Old Feb 19, 2025 | 09:42 AM
  #6  
ssmiller60's Avatar
Junior Member
 
Joined: Sep 2016
Posts: 17
Likes: 5
2014 E550 coupe
update

Replying here to confirm everything is still attached and I've had no problems. Hope that helps.
Reply
Old Mar 1, 2026 | 01:44 PM
  #7  
Seiko's Avatar
Newbie
 
Joined: Feb 2026
Posts: 6
Likes: 3
2017 GLE-350 4MATIC W166.057 A89 276.955 722.906
Moved to W166

https://mbworld.org/forums/gle-class...st#post9268426

Last edited by Seiko; Mar 1, 2026 at 04:21 PM. Reason: Posted to the Wrong Sub-Forum, Moved to W166
Reply
Old Mar 1, 2026 | 03:06 PM
  #8  
CaliBenzDriver's Avatar
Out Of Control!!
Community Builder
Community Influencer
Liked
Community Favorite
 
Joined: Apr 2019
Posts: 11,921
Likes: 6,775
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
EVERYTHING MUST GO...

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.
Reply
MB World Stories

The Best of Mercedes & AMG

story-0

6 Mercedes Models That Did NOT Age Well (But Are Somehow Still Cool)

 Verdad Gallardo
story-1

Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun

 Verdad Gallardo
story-2

Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren

 Verdad Gallardo
story-3

8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine

 Verdad Gallardo
story-4

Flawlessly Restored Mercedes 190E Evo II Heads to Auction

 Verdad Gallardo
story-5

Electric Mercedes C-Class Unveiled: 11 Things You Need to Know

 Verdad Gallardo
story-6

Mercedes EQS Gets A Major Update: Everything You Need to Know

 Verdad Gallardo
story-7

5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve

 Verdad Gallardo
story-8

Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping

 Verdad Gallardo
story-9

10 Most Reliable Mercedes-Benz Models You Can Buy Used

 Verdad Gallardo
Old Mar 1, 2026 | 04:24 PM
  #9  
Seiko's Avatar
Newbie
 
Joined: Feb 2026
Posts: 6
Likes: 3
2017 GLE-350 4MATIC W166.057 A89 276.955 722.906
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!
Reply
Old Mar 1, 2026 | 04:43 PM
  #10  
CaliBenzDriver's Avatar
Out Of Control!!
Community Builder
Community Influencer
Liked
Community Favorite
 
Joined: Apr 2019
Posts: 11,921
Likes: 6,775
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
limit is narrow

Originally Posted by Seiko
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...

Last edited by CaliBenzDriver; Mar 1, 2026 at 04:59 PM.
Reply

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 


You have already rated this thread Rating: Thread Rating: 0 votes,  average.


All times are GMT -4. The time now is 03:05 PM.

story-0
6 Mercedes Models That Did NOT Age Well (But Are Somehow Still Cool)

Slideshow: Not every Mercedes design becomes timeless, some feel stuck in the era they came from.

By Verdad Gallardo | 2026-05-12 18:09:07


VIEW MORE
story-1
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun

Slideshow: Yes, Mercedes built manual cars, and some of them are far more interesting than you'd expect.

By Verdad Gallardo | 2026-05-02 12:36:58


VIEW MORE
story-2
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren

Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.

By Verdad Gallardo | 2026-04-29 11:19:28


VIEW MORE
story-3
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine

Slideshow: Before curves took over, Mercedes mastered the art of the straight line, and some of those shapes still look right today.

By Verdad Gallardo | 2026-04-25 12:05:49


VIEW MORE
story-4
Flawlessly Restored Mercedes 190E Evo II Heads to Auction

Slideshow: The 190E Evolution II shows how a homologation necessity became a six-figure collector icon.

By Verdad Gallardo | 2026-04-22 17:53:47


VIEW MORE
story-5
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know

Slideshow: Mercedes is turning one of its core nameplates electric, and the details show just how serious this shift is.

By Verdad Gallardo | 2026-04-21 13:58:06


VIEW MORE
story-6
Mercedes EQS Gets A Major Update: Everything You Need to Know

Slideshow: Faster charging, longer range, and a controversial steer-by-wire system define the latest evolution of Mercedes-Benz EQS.

By Verdad Gallardo | 2026-04-15 10:35:34


VIEW MORE
story-7
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve

Slideshow: These overlooked Mercedes-Benz models never got the spotlight, but they quietly delivered more than most remember.

By Verdad Gallardo | 2026-04-13 19:35:45


VIEW MORE
story-8
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping

Slideshow: A well-used 1991 Mercedes-Benz 300D with more than one million miles is now looking for a new owner, and it still appears ready for more.

By Verdad Gallardo | 2026-04-10 10:05:15


VIEW MORE
story-9
10 Most Reliable Mercedes-Benz Models You Can Buy Used

Slideshow: From bulletproof sedans to surprisingly tough SUVs, these Mercedes models proved that the three-pointed star can go the distance.

By Verdad Gallardo | 2026-04-08 09:55:49


VIEW MORE