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- Applicable Models
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- 6 Comments
Applicable Models:
- Mercedes-Benz C350 (2008-15)
- Mercedes-Benz GLK350 (2010-15)
- Project Time: 2 hours
- Tab: $30 to $150
- Talent
- Tools: E10, E12 Torx sockets
- Parts Required: Tensioners
- Performance Gain: Quiet Engine
- Complementary Modification: New Tensioner
The idler or guide pulleys in the W204 C350 sits above and to the left of the coolant pump pulley and are high tension stress points in the belt system on your car.
It can fail over time and usually will let you know it is going bad by starting to make a whining sound. If the pulley starts whining you should replace it right away, as it will only get worse and then fail completely. While you are performing this work you should also check your V-belt for wear, cracking, fraying, delaminating and drying out. If your belt shows any of these signs you should replace it. I recommend you buy two belts and always keep an extra one in the car. You don't want to be stranded on the side of the road for the lack of a spare drive belt.
Replacing the idler pulleys on your Mercedes-Benz W204 is one of the easier jobs you will do. You should be able to do it in well less than two hours. It is a great starter project if you are just beginning to DIY or "Do It Yourself" on your car.
Let the car cool so you don't have to work around a hot engine.
Hot tip
Don't throw out your old hardware
Steve Vernon, DIY Expert
Project Photos
Ozmo
October 26, 2023
Great information, I did what you said, done in less than 1 hour. Great asset you have here.
Followup from the Pelican Staff:
Thanks for the feedback. Glad it was helpful! - Nick at Pelican Parts
Emad
June 5, 2023
Thank you for the very detailed and sufficient information. but I have one comment, you are specifying the case model name W204, however, the M272/m273 comes on a vast variety of models such as W211, W221, etc. i prefer if you add the engine name, not the car model. and add the applicant car models under the engine name.
Followup from the Pelican Staff:
Yes, only the single engine is covered here. Thanks for the feedback. - Nick at Pelican Parts
Tim B
August 22, 2022
Good write-up. I have a 2010 C300 4matic Sport with the 272.948 and used an E12 and E14 for the two pulleys, forget which was which. The manual I used says torque to 35nm for initial installation and 25nm for follow-up operations. The INA upper idler pulley came with a new bolt so I went with 35nm, the smooth pulley didnt come with a new bolt so I cleaned and reused the old bolt, torqued to 25nm. Make sure to remove the pullies off slowly and check for any washers that may be installed.
Followup from the Pelican Staff:
Tim, thanks for all the recent feedback and comments. We appreciate the value you are adding to the tech articles. - Nick at Pelican Parts
Jason
March 14, 2022
RE: Don't throw out the old hardware until you see what comes with the new pulleys. These bolts are micro-encapsulated and considered single use only by Mercedes Benz.
So what do you do if the replacement part doesn't include a new bolt? I wasn't offered offered a bolt for the idler pulley without one when I placed my order? Seems as though the old bolt could be reused.
Followup from the Pelican Staff:
You can re-use the fastener, as long as you clean the threads thoroughly and reapply the same threadlocker. - Nick at Pelican Parts
Joseph
February 6, 2022
On my 2011 GLK350, the smooth idler pulley used an E14 head bolt, not an E10, as was the replacement bolt I ordered from Mercedes 0019904803.
Since this page covers both the W204 and X204 platform, the E14 might be GLK-specific.
Followup from the Pelican Staff:
Thanks for the Info. We appreciate it. - Nick at Pelican Parts
Chiefplumber
February 6, 2019
I always appreciate the direct step by step instructions which make the task go smoothly. I replaced both idler pulleys, the tensioner and the serpentine belt in about an hour. Thanks so much for the pictures and steps.
I have two comments on the overall task. First, I have a 2010 C300 and Mercedes used E12 and E14 Torx bolts for the pulleys. Second, when replacing the tensioner save the pin that comes in the new tensioner. If you ever need to perform the job again, use the pin you saved. You won't need the 4mm allen key and you won't need to recover the allen key/pin when you finish the job!
Followup from the Pelican Staff:
Thanks for the additional info and feedback. We appreciate it. - Nick at Pelican Parts
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Technical Forum Message Board Reader Questions About this Article
Applicable Models:
- Mercedes-Benz C350 (2008-15)
- Mercedes-Benz GLK350 (2010-15)
