[MillTek]

Hi,
While investigating a weird noise I posted about earlier tonight I noticed that there's a tear in one of the edges of the accessory serpentine belt so I guess I'll replace it. While searching this forum I did not come across a diagram of the belt routing or any information about how to do it. Anyone have any ideas?

Also, I did find several posts about bad pulleys and/or belt tensioner. Is there any instructions for replacing these anywhere that I can access??

Thanks

 

[a02stang]

most of the pulleys just have a single bolt holding them on. the tensioner has a 17mm. to replace it you will have to take the tension off...then on the underside their is a opening that you have to stick a pin into to lock the tensioner to access the 2 bolts.

 

[MB-SV]

This happened to my 2008 C300 at about 112K miles, about $450 to have belt, tensioner and pulley replaced. How many miles on your 2009 when this started making noise? My C300 made the noise first thing cold in the morning and it gradually worsened.

 

[MillTek]

Hi,
Thanks for the information and the diagram a02stang. Really helped. Working that tensioner without knowing about the 17mm tension relief would be an absolute bear!!

I really depend on the car for work so I went to the dealer and got a belt ($50), Sheave Pulley ($47.50), Guide Pulley ($55) and Belt Tightener ($177). I know I could have got clone parts for a lot less but whatever else about Benz, their parts are pretty good. I also probably didn't need to replace the tensioner but I read somewhere here that the newer version is better.

Anyway, the bearing in my guide pulley was trashed and that had frayed the side of the old belt. That presumably was the cause of the noise. It's gone now. The noise started about a week ago and sounded like a bit of dirt on the belt. Last night when I pulled in to the house and opened the door the noise was awful. So it looks like they can squeak fairly quietly for a while and then collapse.

MB-SV, mine is a 2009 with only 37K miles on it so you did well. I asked a tech at the dealership and he said if you are behind one or more vehicles that are throwing grit up from the road that can cause premature failure. Who knows?

I used to have a 1989 190E and when the guide pulley on that died the new one had a plastic disk that totally covered the front of it so presumably that would stop grit getting in??

 

[a02stang]

dude honestly i don't think dirt can cause a noise, mb has come out with multiple attempts to fix these chirping noises. trying to shim idler pulleys and what not. now they are seeing its the tensioners. along with possible worn drive belts. if you go to your local parts shot they give away engine belt depth gauges. if you place that in your belt and you cant see gauge the belt ribs are worn too deep and can cause noises.

 

[MillTek]

a02stang,
I didn't explain properly. When I said it sounded like dirt on the belt I was comparing it to a noise I had in another car years ago after I drove though a muddy puddle in a building site and some of the belts got muddy water splashed on them and made a weird chirpy noise for a day or so.

On the 190 E I had, the improved pulley was bolted on with a recessed hex bolt and a plastic shield with a hex piece in the middle pushed into the bolt after it was tightened. That way, any dirt or grit particles that made it in couldn't get into the bearings.

 

[a02stang]

oh ok.

 

[MB-SV]

I was told (in the case of my 08 C300) that as the tensioner begins to fail and starts making noise when cold, the belt gets grooved and shredded gradually.

Yes, to my untrained ear the chirpy sounds when cold sounded like a belt problem and it just got worse.

 

[Rjones383]

most of the pulleys just have a single bolt holding them on. the tensioner has a 17mm. to replace it you will have to take the tension off...then on the underside their is a opening that you have to stick a pin into to lock the tensioner to access the 2 bolts.

My tensioner is bad also. Thanks for the drawing. I was quoted $475 to replace the tensioner and belt but honestly, this only looks like and hour job. I'm just going to go ahead and do it myself. My car is doing as described above. Making noises while cold but it stops after the car is warmed up. I have a 2008 with 90k miles.

 

[Rjones383]

one more question. Does anyone know if the two idler pulleys are the same part #?

Thanks

 

[MB-SV]

My tensioner is bad also. Thanks for the drawing. I was quoted $475 to replace the tensioner and belt but honestly, this only looks like and hour job. I'm just going to go ahead and do it myself. My car is doing as described above. Making noises while cold but it stops after the car is warmed up. I have a 2008 with 90k miles.

That's how my noise started and in a few weeks it was much louder.

 

[bujapeople]

Hey I am having exact same issue. By replacing the pulley and tensioner fix the issue?

 

[MB-SV]

and belt too

 

[FCP Euro]

Replacing the belt and pulleys with a kit like this one (click image) will solve the issue. What I normally see is the bearings in the idler pulleys going bad first, rarely does the tensioner give issues however it's good practice to do the tensioner at the same time.