rh71

It's a '10 C300. Halfway through I close the hood and it still seems louder than what it once was. Opinions? Ideas?

rh71

can you guys confirm at least if it's louder or more awkward sounding than you're used to?

rh71

*bump* getting pretty obvious that it's louder than it should be. Even in the cabin while idle and during acceleration. Nobody has seen this before? Sounds like I'm operating a hovercraft or something.

Not due at the dealer for the annual oil service until September and if I bring it in just for this they'll probably charge an hour just to look at it.

Paddlefoot64

My 2010 C300 is very quiet at idle. Maybe a bearing (water pump or alternator?) has gone bad.

AkaSigFreak

My 08 C300 was incredibly quiet. Why is the engine bay so filthy? Did this car get run through deep water or something? Can you see the pulleys? Are they covered with dirt like the rest of the engine bay?

MDMercedesGuy

Definitely something like an idler pulley bearing is going out.

I'll second AkaSigFreak - that engine bay, particularly the amount of dirt near the air intake is one of the dirtiest I have ever seen on a road going car. It makes me wonder what could have gotten into the bearings and caused premature wear.

One thing is for sure - stop driving the car until you get it looked at. Putting something like this off only makes for more dollar signs later and that definitely does not sound good.

C300Sport

Im with Sig and MD. The unusual amount of dirt has likely caused premature aging onmost everything under the hood. I coudln't hear anything in particular but it did sound like a lot of "friction" causing an overall loud engine.
Get it cleaned up and checked out and hopefully it won't be anything major. Be sure whoever works on it knows what they are doing....you don't want some shop flunky blasting away with steam and water under there just to make it look pretty and end up in worse shape than before.

C300Sport

Did you check the condition of your air filters?

Glyn M Ruck

Idler or tensioner on it's way out is most likely.

rh71

thanks - may be when the landscapers use the leaf blower around the garage area it all gets tossed in there. No other reason why it would be unusually dusty that I can think of - surprised that doesn't happen more often to others? Bringing it in Fri. From a little bit of searching, the entire pulley should be less than $50. But of course there's labor.

AkaSigFreak

I can't imagine that kind of dirt from a leaf blower. It almost looks like the car was run through some deep, muddy water and wasn't cleaned afterwards.
Good luck with the repair. Hopefully its something simple.

rh71

nope, between a 3 mile commute to a quiet parking lot at work and sitting in the driveway most weekends, that surely has not happened. I think it's only got 10k miles in nearly 3 years.

Weird. We'll try and get it cleaned up and see how it gets again over time.

One other thing I should mention is that because of the low mileage, we had only been doing the oil changes (but full Service A after year 1). We skipped Service B (just did oil/filter change last 2 years) but I don't think there's anything in there that says replace something. Both A & B say check and clean air filter. Does the air filter not get replaced? I will check the filter out if someone can point me to where it is. Some other thread indicated it was under the glove box in the interior? Or maybe I'm supposed to look at the engine air filter --> https://mbworld.org/forums/c-class-w...tallation.html I didn't find it in the online manual I have.

frogs9497

If I dropped $30k+ or $40k+ on a car and were concerned about an unusual engine noise, I wouldn't hesitate to pay the dealer to check it out. That said, I think my MB dealer would at least diagnose the issue before charging me. Either way, I'm not taking that risk.

rh71

almost forgot to update the thread... they found it was the alternator (bearing) that had to be replaced which was under warranty still. Probably explains why the first battery only lasted 3 years and they put a new one in last year. They said it's nothing we caused since there's a cover on the bottom and sometimes these things just go bad. They didn't say anything about the dirt. I gotta say it doesn't look that different in terms of cleanliness than my car parked elsewhere.

CzchMex

Obviously the people mentioning about the dirt being a culprit have never driven where dirt is prone. Trucks. Farm vehicles. Desert locations. All have tons of dirt. But those cars don't fail early. Dirt will not get into a sealed bearing unless the bearing was bad to begin with. Lol...dirt

Glad you found it. Definitely sounded like a bearing.

Also if you change your oil with full synthetic you will be ok with the length of time between changes. Synthetic oil takes a lot longer to break down then conventional oil

C300Sport

It's funny when people are so sure they have everyone else figured out...
I spent the first 19 years of my life on a farm down a dirt road from the main road. Yes, our engines got pretty dirty but that was in the days of completely open engine bays and minimal airflow management. Today's cars tend to route clean air around the engine, greatly reducing the amount of "dirty air" blowing around everywhere. Even the switch from belt driven to electric driven cooling fans has reduced the "dust cloud" effect from the old belt driven, non clutched cooling fans running over dry pack.
Anyhow, his engine is dirty and dirt can indeed cause all types of mechanical maladies...just ask any military mechanic that has worked in the dessert.

CzchMex

Well said. +1

robnyc

very similar sound on my car too after a small accident in a black ice street, i hit a parked car and had to replace my passenger side headlight, bumper, fog led .. I believe this is a result of the accident.

Mechanic thought it could be a idle pulley or alternator as well after further investigation he called met his morning saying its the ac/air compressor and that he doesn't see any visuals of it being damaged from the accident.

I called my previous insurance to let them know of this, I just switched to a different insurance 1 month after being fixed. Any advice?