C250 serpentine belt replacement
04-20-2019, 05:14 PM
#1
Member
Thread Starter
C250 serpentine belt replacement
I recently changed the serpentine belt on my girlfriend's '14 C250. I had searched here ahead of time to find any info about the job and hadn't found anything for the C250 other than a thread in the coupe forum. I updated that thread, but figured I would stick the same info here in the sedan forum, too.
Other than the fact that (as far as I can tell) you need to access the belt from underneath, it's not that difficult. In addition to the little socket needed for removing the under panels, you need a T60 bit** to take the tension off the tensioner, and then something a couple/few inches long and thin (I used a small allen wrench) to "lock" the tensioner in the untensioned position so you can get the old belt off and the new belt on.
[** - I used a T60, because that's what I had. It fit perfectly fine. However, it looked to me like the star opening may actually be a Torx Plus. Hard to tell, since I obviously couldn't get a straight-on view to clearly see the shape of the star.]
Pic from above. Nope, not getting to the belt from here! The intake tract is very much in the way of getting one's arms down in there, and removing that intake pipe is not a trivial task from what I could see. So, to the lift we go!
Looking up from underneath I drew myself a diagram so I knew where I needed to route the new belt.
Although access from below is better, it's still not great. If you've got fat or short arms, it's gonna be tough. But there are gaps on both sides (on either side of the cooling fan, yellow arrows) where you can reach in/up to get to the belt.
Looking up on the passenger side. Crank pulley is out of view off the right side of the picture.
Looking up on the driver side. Crank pulley is in the bottom left of the picture, with the tensioner pretty much in the center of the picture.
I used a T60 Torx bit on a 1/2" ratchet to loosen the tensioner; with the handle of the ratchet pointing towards the passenger side, I pulled down to take tension off the belt. In order to have both hands free to manipulate the new belt into position, I "locked" the tensioner by putting an allen wrench through a small hole on the tensioner so that it would catch on the bracket or whatever was behind the tensioner. I assume that's what that hole is there for; if not, it came in handy anyway!
Once I had the new belt properly routed, I used the wrench and T60 to take tension off the allen wrench, pulled the allen wrench out, then gently let the tensioner put tension on the belt. Good to go!
Bonus picture of the underside of a C250 automatic with the 3 front underpanels removed. (Two pictures pasted together, so there's some mismatch due to parallax.)
Other than the fact that (as far as I can tell) you need to access the belt from underneath, it's not that difficult. In addition to the little socket needed for removing the under panels, you need a T60 bit** to take the tension off the tensioner, and then something a couple/few inches long and thin (I used a small allen wrench) to "lock" the tensioner in the untensioned position so you can get the old belt off and the new belt on.
[** - I used a T60, because that's what I had. It fit perfectly fine. However, it looked to me like the star opening may actually be a Torx Plus. Hard to tell, since I obviously couldn't get a straight-on view to clearly see the shape of the star.]
Pic from above. Nope, not getting to the belt from here! The intake tract is very much in the way of getting one's arms down in there, and removing that intake pipe is not a trivial task from what I could see. So, to the lift we go!
Looking up from underneath I drew myself a diagram so I knew where I needed to route the new belt.
Although access from below is better, it's still not great. If you've got fat or short arms, it's gonna be tough. But there are gaps on both sides (on either side of the cooling fan, yellow arrows) where you can reach in/up to get to the belt.
Looking up on the passenger side. Crank pulley is out of view off the right side of the picture.
Looking up on the driver side. Crank pulley is in the bottom left of the picture, with the tensioner pretty much in the center of the picture.
I used a T60 Torx bit on a 1/2" ratchet to loosen the tensioner; with the handle of the ratchet pointing towards the passenger side, I pulled down to take tension off the belt. In order to have both hands free to manipulate the new belt into position, I "locked" the tensioner by putting an allen wrench through a small hole on the tensioner so that it would catch on the bracket or whatever was behind the tensioner. I assume that's what that hole is there for; if not, it came in handy anyway!
Once I had the new belt properly routed, I used the wrench and T60 to take tension off the allen wrench, pulled the allen wrench out, then gently let the tensioner put tension on the belt. Good to go!
Bonus picture of the underside of a C250 automatic with the 3 front underpanels removed. (Two pictures pasted together, so there's some mismatch due to parallax.)
04-27-2020, 12:46 AM
#2
Reviving an old thread. Is there a certain mileage it's recommended to do the serpentine belt?? No info whatsoever in the maintenance schedule. Normally it's something like 80k I believe?
04-27-2020, 12:58 AM
#3
Senior Member
Hi,
I did mine at 100,000KM and changed the pulley on the tensioner at the same time.
When you have the belt off carry out a test of the sprag one way clutch bearing inside of the alternator pulley mine was seized and making intermittent strange noise when idling and did not realise what the problem was when replacing the belt thinking it was the belt or plastic idler pulley related.
I did mine at 100,000KM and changed the pulley on the tensioner at the same time.
When you have the belt off carry out a test of the sprag one way clutch bearing inside of the alternator pulley mine was seized and making intermittent strange noise when idling and did not realise what the problem was when replacing the belt thinking it was the belt or plastic idler pulley related.
06-08-2023, 01:05 PM
#4
I apologize for bringing up this old thread. I had a similar issue with my vehicle recently; I had a visible crack in my serpentine belt. I get a proper tool for the DIY and then follow certain procedures on how to replace it. I came across an in-depth article that may be worth reading. Search for "Mercedes-Benz Serpentine Belt Replacement Guide on YOUCANIC" and you will see an article that goes over common causes and possible fixes. You can read about it yourself. I hope this information can assist someone else with a similar issue.
