Hey guys, on my sisters 2011 c300 sport there is an odd noise coming from the engine bay. It sounds almost like a lawn mower, or more precisely, like when you used to put a baseball card in the spoke of your bicycle rim when you were a kid. Sort of like that clicking, ticking noise. I believe the noise is coming from just beyond the driver side firewall, as I hear it louder from the left side in the passenger seat.

It happens under engine load and gets louder with higher rpms. Usually starts around 2500 or so rpm and clicking gets louder/faster when higher rpms. I have searched google and these forums and came up empty handed on the w204. However, with the w203 a "erroneous fuel vapour purge valve" or fuel purge valve for short was a common problem and describes this almost exactly. Either way the car is less than 3,000 miles on the clock and certainly covered under warranty, so I will be traveling to the dealer. However, my dealer is very lazy and prone to (can't replicate it, sorry) or, that's normal, deal with it attitude. Not very helpful at all; but if I sound like I know what I am talking about, they do something.

So before I go talking about a purge valve or its mount making a problem, anyone have any other suggestions or recommendations as to what it could be?

On a side note, car is getting pretty poor MPG compared to my 2009, she gets 19 and change, I get near 24mpg. She does more city driving, but not that much more to account for that difference. I know mine was bad on gas the first couple thousand miles, but I never remember averaging 19...

Lastly, her power steering is much louder than mine and her car has a much worse drone noise, but I don't think her car was considered part of the power steering recall MB issued, right?

Tell the dealer to check the purge valve & it's rubber mounting if it has one. All SA cars should have the purge valve mounted on rubber. Make them replace the purge valve if it's noisy.

Does the PS make more noise at full lock? If so it is low fluid level & air is shreeking through the pressure release/relief valves. Top up the fluid to the correct level & repeatedly - 5 or 6 times - turn the steering from lock to lock to bleed the system. Then you might have to top up further. These systems are very level sensitive.

The recall was a re-torque of the PS hose coupling. The car might have leaked a little fluid.

Good luck!

What a timely post. I just noticed something similar on my brand new (delivered less than two weeks ago) 2011 C300 luxury. It first appeared last night driving at highway speed, and definitely sounds like cards shuffled through bicycle spokes. Thing is, from my perspective in the driver's seat, the sound seems to be coming from the passenger rear side? I'm going to run it again today at high speed to see if the noise recurs.

I can't really narrow down where the noise is coming from, in my opinion it sounds right by my feet in the engine compartment, but I could be wrong, I was only in it for 10 minutes or so. Maybe it is a problem with 2011. Her's is a South Africa build, and so is my 2009, so I doubt its related to SA.

In regards to the power steering, it just has a bad drone all the time when moving the wheel in any direction at slow speeds (goes away at faster speeds). It doesn't get any worse on full lock from either side besides for a loud knock and then the drone surges for a second and returns to normal drone). But not only her power steering, but her car in general just "whines" where as I hear more muscle or engine in mine.

I can't seem to find any of the fluids I need to check levels for besides the washer fluid and brake fluid. Lol, any tips?

If its the Purge valve - It is mounted straight in front of the driver on a US car with pipe running to the saddle tanks & filler at the rear.

If the PS pump just drones make them replace it.

The PS reservior & calibrated cap is under the RHS air intake tube facing the engine compartment from the front. Pull off air tube to access.

Thanks Glynn, it was in fact the Purge valve, they are replacing it now, hopefully the sound will be gone after that. I also mentioned that the 2011 had a recall on the Power steering but he denied such a fact (maybe I was mistaken) they are taking a look into it regardless; will let you know how I make out. Thanks for all your help!

Great - darn purge valve - They usually go about 80,000 miles before they get noisy. Pleased they are replacing it. Some are noisy - some are not.

Take no nonsense from them on the PS recall. It's well documented & they have the VIN numbers for which unit's require re torqueing

Yeah, well, at first he tried to B.S. me saying its "normal" but then I informed him my 2009 c300 nor my grandmother's 2008 c300 have this sound. Then he had me take him for a test drive, and oh how the story changed. I hate how they treat everyone like a moron until you prove to them otherwise.

He said the recall was only for 2010 models, but I think he is just bsing and doesn't really know anything. I will see what he says when I get his call later today or tomorrow and if it still has the problem, I will complain or take it to another dealership.

I believe the recall is only 2010's. However it's not every 2010. As was stated before, the dealer can look up the vin to see if yours qualifies, you should have also received a letter in the mail. I have a 2010 and dealer checked and my vin was not included.

Apparently the Purge Valve was not the only thing that was attributing to the sound, after they replaced it they still heard a slight rattle. Turned out to be a loose exhaust clamp or something, so they fixed that issue and now everything is in tip-top shape.

The P.S. was not part of the re-call, but they did confirm that it was a bit "noisy" so they replaced that as well. Thanks for all your help guys, everything is back to the way it should be now. Hope you figure out what is causing your rattle Iggier.

That's good news - The way it should be. Pleased it did not end up in a fight. Benz knows full well that they have the odd noisy PS pump & the clicking purge valve problem goes back a long way. That's why I enjoy my dealership. It's owned by Benz & if you show the service manager a problem he just instructs his team to fix it or replace it depending on the fault. He has an attitude that if you buy a Benz from them you own a few bricks in the walls of the building - how refreshing not to have BS.

hi guys ,i just bought a 2010 mercedes c 300 .the car is running good but i noticed a clicking noise when the car is on p .on drive or reverse the noise is gone .does anyone experiencing the same ?thanks