tpdietz

My vehicle: 2008 C300 Sport 4-matic 79,000 miles.

So two days ago we had our first really cold morning (-8 degrees Fahrenheit). I'm not sure if the temperature is relevant but, that day I noticed a chirp from the engine. The chirping repeats in sync with the cycle of the serpentine belt. It's not loud enough to hear from inside the vehicle (windows closed). Nothing (belt or pulleys) appear to be wobbling. I've done a lot of searching online and have decided it has either has to be the belt tensioner, or the idler pulley(s) (maybe both). Apparently our engine has two idler pulleys. From what I've read there is one near the top left, and another one closer to the center.

A few questions:
- Is there anyway for me to know if the tensioner is bad? Should I just suck it up and replace the tensioner for good measure while I'm down there anyway?

- Any idea's on part numbers for the idler pulleys? According to genuinemercedesparts.com they are different (I've deduced this because they are different prices) On amazon.com I have entered in my vehicle information and have found both the tensioner and a idler pulley that supposedly fit my vehicle for much less than genuinemercedesparts.com, however, only one idler pulley is listed and of course I have no idea which one. Any suggestions on where to purchase these pulleys would be greatly appreciated.

- I bought the vehicle at 59k and I am not sure the last time (if ever) the belt has been replaced. I would imagine it hasn't. Is it recommended to replace the belt while I'm working in that area? If the belt appears okay, should I leave it be? I have found no conclusive answer on the longevity of these things.

I am new to the "working on your own car" hobby and would appreciate any tips or concerns.

Thank You
Troy

Domm

I have roughly 45k miles on my 2008 and the belt has yet to be replaced. It has been extremely quiet and has no signs of cracking, but the belt on the corolla has been changed three times and has 38k miles. I'd imagine at 79k, the belt would need servicing regardless of the quality.

The worst thing about a chirp is the trial and error of finding what's causing it. I would try replacing the belt first since it's the simplest fix. While the belt is off, rotate the pulleys to make sure they are moving freely. Once you've changed the belt, move on from there.

Assuming the process is similar to any other car (I have yet to attempt a belt change in this car), take a picture so you know how to put the new belt on. Have an extension to your ratchet or you'll regret it (leverage is key when loosening the tensioner). If you can, find someone to assist you when putting on the new belt. It may be difficult to loosen the tension while weaving the belt through the pulleys.

Bosnia1992

I had a chirping noise when they replaced mine. ill let you know what they replaced on mine to fix the problem when I'm home.


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tanktube67

Sometimes the serpentine belt appears to look good, on my experience the belt wears out, I will recommend to replace the belt first if the chirping persist definitely it will be the tensioner.

09C2304MATIC

I had a loud chriping sound on cold starts (-26 degrees celcius). It got worse in the past few weeks. Dealer suggested a new belt. The belt looked fine, but I thought for the $61 I'd have it done. I told them to leave the car outside for a few hours then to start it in order to replicate the nosie. Dealer called me back on Monday, and said that they also hear a groaning sound. They ended up replacing the belt tensioner assembly and an idler pulley, as well as the belt. I asked to keep the old belt as a spare, which still looked in perfect condition (51,00kms). I have been driving the car for the past few days. there is no noise anymore. The engine is quieter, and even the braking idle is a bit smoother (which is an ongoing problem with my car). The pulleys were replaced on my extended warranty. I had to pay for the belt / belt install. I am glad I purchased the extended warranty. I believe that my belt was ok from the start, and the culprits were always the pulleys. My car is a 2009 C230 MATIC - 51,000kms (Canadian Issue Car).

Bosnia1992

first they replaced upper and lower pulleys ( sheave and guide pulley) part numbers : 272 202 10 19
and 272 202 14 19 and that only fixed it for about two months then they replaced the belt tensioner 272 200 02 70 and problem has been gone since last year.


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illlojik

I'm at 53000 on the dot today.
I started getting an annoying squeak once the temps dropped below 30. It worsened over the past month or so. I finally ordered a new Belt (Gates Belt: They manufacture both our belts and tensioners btw) The noise went away for 2 days. I can hear a very low squeak intermittently at cold starts, so I went ahead and ordered the tensioner. Which I plan to put in this weekend. Since I see no DIY how too's I'll try my best to take pics. It's cold as ***** out here so That's a big if.

Boydigital1986

I just went through this! My car only has 50k miles and the belt started squeaking and then the guy at Jiffy Lube noticed that it started to shred slightly. I took it to Mercedes and they replaced the two idler pulleys and the belt tensioner. I also have a 2008 C300. The mechanic told me it's a known issue with the 2008-2012 models. However, the replacement should be fine for another 5-6 years.

tpdietz

Let me know if you do this. I'd be eager to hear if you ran into any problems. Seems like a pretty straight forward job.

Do you mind if I ask what the final cost was at the dealership?

illlojik

The job was actually straight forward. There's limited space, so getting to the bottom tensioner bolt was trouble without having a holding pin to keep the tensioner pulley wheel out the way. It took me 1 hr 3 minutes. Ok consider it was raining and most of that was plastic bag prep to cover the engine.

tpdietz

Thanks for part #'s!

I ordered: new belt, upper pulley, lower pulley, and Gates tensioner. Parts should be in within a week. Total cost: ~$145 incl. shipping costs. I would not be surprised to see this job costing over $500 at the stealership.

Thanks for your response. I do have a set of pins, so hopefully this will be a non issue.

Does anybody out there know the torque (nm) of the bolts (pulley's and tensioner)? I've been searching around and haven't found a conclusive answer.

Richard2011

I just noticed this chirping today, and I'm only at ~28.5K miles. Sounds like the same issue. I'll take it to the dealership tomorrow.

nnkfws333

This has been helpful but I had one more additional question. Has anyone used the Gates Belt Tensioner part #38319 ??? Trying to decide to either try this or go with the Ina part #2722000270. Just trying to see if anyone had problems with the Gates one or not or are they exactly the same?

tpdietz

I bought the Gates off amazon. So far so good, I wouldn't hesitate to recommend you do the same.

black lavender

Just to comment, I had the same chirping/squeaking by the belt area. Dealer replaced the tensioner and v-belt.

The mechanic said the belt was about to fly off the pulley...

nnkfws333

Well I got the Gates tensioner off of Amazon, , and it didn't work for my 2009 W204 C300 Sport 6 Speed Manual. On the back of the tensioner, where the shock absorber attaches, there is a screw that secures the shock absorber to the tensioner but the tensioner doesn't have threads for the screw. I wasn't going to put on the tensioner without the screw so I am just going to go for the oem part off of Autohausaz. Maybe some C300's don't have the shock absorber for the tensioner but I doubt it. Hope this helps someone in the future.

Cy3

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