mike62

Recently noticed this sound becoming more frequent over the past few months. Hard to describe, sounds like hi pressure air escaping with a little tapping. Doesn't always follow engine RPM. At times it will stay constant, fading in & then out. Other times, it happens for a few seconds, then cuts out abruptly. It's heard more in the cabin, seemly in front and toward the left of you, not as much with window down. No exhaust smoke or oil level change on the stick. Getting good MPG, performance not affected adversely. Just a nagging sound? or valves need adjusting? Maybe manifold gasket? Got suggestions? Puzzled!

ohlord

start the engine.Listen at start up if you hear the tap tap tapping of the purge valve located on the drivers side above the wheel well.
Diy cleaning procedure on www.benzworld.org w210 forum


it is stamped MOT

RichardM98

While the sound you describe sounds like the purge valve as ohlord mentions, I'd be surprised if you could hear it while in the cabin with the motor running and the hood closed. I can only hear mine while standing next to the left side of the car with the hood open. And yes my hearing is still adequate.

There are some vacuum operated 'doors' in the heater case and maybe the sound could travel to the left air nozzle but that's all I can think of. Just my $0.02.

Good luck.

01BlackE320

I hear mine from in the cabin sometimes when I'm waiting for a light. I know exactly what it is and it never bothers me. I love how quiet and tight my E320 is for a 10 yr old car

mike62

Guys-

Thanks for the input a while back on this, re: valve adjustment thread.
What does the MOT do? Asking because I had a "check engine" light and dash message "check engine electronics" come on today. Coincidentally, right at 140K miles. Engine sounds the same, MOT taps the same. No obvious problems. Suggest replacing this MOT? Get a computer read and clear the codes? Looking for suggestions please.

ohlord

are self adjusting.
get the codes read or go to harborfreight and buy a code reader and read them.
We need to know whats up in order to figure out what's up.