pcy

Hi,

On my '07 C280, when I don't have stereo on, I noticed a knocking noise coming from the passenger side rear (near fuel filler neck) area.

Symptoms:
- knock, pause of about 3 to 5 seconds, then knock, pause of 3 to 5 seconds, ...
- one knock at a time.
- this knocking noise ONLY is heard after the car comes to complete stop with brakes on. Again, the car is at 100% standstill.
- the sound is similar to tapping on the car body panel with back of the finger

I remember seeing another thread within the recent past regarding the similar issue. I am not able to find that thread.

Any one has any ideas where the noise is coming from?

LILBENZ230

That was my thread, I think. Mine sounds like I have someone trapped in the trunk. A few other people posted that their cars do the same thing and always have. I just laugh about it now when people are in the car and tell them I have my boyfriend locked in the trunk.

I think we decided it was fuel level sender units banging around in the tank, by the way.

pcy

Matt, does your car still make that noise?

Glyn M Ruck

I still suspect that one of the fuel senders has become noisy.

pcy

thanks guys for your feedback. I will continue to monitor the noise and see if it gets worse.

johnand

I remember Sanf had that problem on his 07 when he 1st got it. Don't think he got it resolved before he sold the car. Let me check my TSB's and see if I can find any info.

LILBENZ230

My car always has made this noise and I suppose it always will at this point.. I've had it since 25,000 miles and now am at 96,000.

BigBodyBenzC240

Mine makes same noise as well. No clue what it can be. Any insight onto this anyone?

W203E35

I had this exact same problem and you know what it ended up being???

MY STOCK EXHAUST HITTING THE BUMPER (VIBRATION). I USE TO HEAR THIS WHEN I CAME TO A RED LIGHT. IT WOULD BE WEIRD BECAUSE IT WOULD BE OFF AND ON. NOW WITH MY AFTERMARKET EXHAUST I HEAR IT MORE OFTEN.

pcy

Karo, I can't see how exhaust can make that kind of noise. I checked under the car. Nothing on my exhaust system is loose. I am not saying your analysis is wrong... I am saying I don't see how exahaust can contribute to this noise...

On my car, the noise comes when I stop at a traffic light (after the car comes to a complete stop). No other exahust noises. Clean 'knock'... pause for about 3 seconds... then another 'knock'... another pause...

W203E35

Mine was the tip, my exhaust tip was hitting the bumper cutout. With my new exhaust I hear it more often. Mine sounded like an engine knock but from the rear.

yvanlavoie20

on my c280 2007 4 matic ... i have the same noise, it is the same sound as door locking inside the rear door. my car have 72 000 km now and the sound come only after stopping and hold on brakes, it dont come if i put tranny in neutral.

Yvan

W203E35

I'm not kidding it might be your exhaust. Mine happens the same as well, when I come to a red light and not the whole time..just a little. I know it will be hard to replicate it but sit in the drivers seat and have your friend or someone move the exhaust left and right fast. It should sound similar.

Mine for sure is that.

R. Pizano

I had the exact same sound happen to my 2007 C230WZ. When I took my car in to get serviced, I asked about that noise. I went on a test drive with a mechanic who's been servicing Benz's for 30 years, and he mentioned that this is very common. It's the fueling system, something about a process needed to release some type of vapors (as you can tell, it was very technical, I don't fully remember every detail). The process/cycle only occurs when you are at a complete stop. However, you must be stopped for atleast 10 seconds for the process to fully finish. If you accelerate before 10 seconds, then the process restarts the next time you stop.

I hope that helps clear things up. There's nothing that can be done to prevent that. They have been working on fixing it for newer models.

yvanlavoie20

this is probably the thing i listen

thanks R.Pizano

Yvan

aigooalex

i guess it's an 07 thang? i have the same problem as well... i always think someone is in the trunk whenever the car is stopped in motion.