bnz616

I've had this loud whining sound come up a couple times already. It sounds like a mix between a whining whirling sound. Almost like the supercharger wind sound. It happened three times when it was cold and i started it up for the first time in the morning. It went away after i turned off the car and started it back up. This happened a few weeks ago. I thought it was just related to starting the car up on a cold day. Today, after parking in an underground garage for like 10 hours, i started the car and drove to another parking lot a few blocks away and parked, opened the door and noticed that the same whining sound was going. I turned the car off, turned it back on and everything was normal again. Any idea what this noise is?

It whines changes in frequency? pitch? when I rev the car. I couldn't isolate the noise to the exact location because I turned off the car right away again.... but it is from the front of the car.

A similar thread regarding this sound....but I heard it even after i drove for about 5-10 mins.
https://mbworld.org/forums/showthrea...t=engine+whine

Another thing I just noticed since I had the radio totally off. Do you guys usually hear the brake light switch click when you step on the brake pedal gradually and when you let go of the pedal gradually?

xqwizit

I've got the same noise in my 2002 C32 (early production, made in 2001). How long have you had yours? I've had mine for two months (bought it used). If you've had yours longer, has this problem recently came up or was it always there and you never noticed it? My car is at the dealer right now and I mentioned this as one of the problems I have but they said that it may be a vacuum pump of some sort simply recharging or the exhaust purge valves. Regardless, I said that it doesn't sound right and it's not always present but when it is, it is very noticeable. I can even hear it on the highway going 80mph. They said that they'd have a tech listen to the engine and make sure that everything that makes noise should be and nothing should be out of the ordinary. I'll report back tomorrow. I'm hoping it isn't something more serious. But if it is, I'd be glad that they at least did something about it. The noise that I hear is definitely coming from the driver's door and is noticeable even with the window up so it's definitely coming somewhere from the drivers side. It could be either inside the driver's front fender or right underneath the driver.

bnz616

The noise I am hearing isn't quite from that side of the car. It sounds like the very front of the car. I haven't taken it to the dealer because it happened only a few times, weeks apart and I know even if I drop the car off to the dealer for a few days, they would never hear it.

I also bought the car used, so I am kind of sensitive about sounds, since I'm not familiar with how everything should sound, like when the car was brand new.

If it does happen again (I'm not sure when, might be awhile), I will try to isolate the exact location the sound is coming from.

MadC32

When I had this problem, I had to replace my air pump. Wouldnt shop whining until I pulled the plug on that thing..

bnz616

Hmm...that might be the problem. Did it happen occasionally until it completely crapped out one day? Which air pump are you referring to? Is it a major repair?

MadC32

exactly.. one day it died lol..

The pump I mean is a bit behind the right frontlight. Wasn't a big thing to repair. Took the mechanic 30 mins to do.

MercedeSChink

I always thought that noise was the s/c kickin in...

xqwizit

MadC32, what did the air pump control? Curious if it's something critical to the operation of the car. On mine, it's a whirring noise and the noise varies with different throttle pressure.

Vadim @ evosport

bnz616: This is common problem on W203s. The noise you hear is a dying secondary air injection pump. It's function is to reduce cold start emissions, this is why you hear at cold start up.

Take the car to dealer, they should be aware of this problem and get it fixed within a day.

Good Luck!

Vader13

or the smog pump

bnz616

Does this secondary air injection pump actually cause any large problems when it starts to fail? I can't repeat the noise for the dealer, so I'm guessing the service advisor is going to give me the excuse that theres nothing wrong. Maybe I might have to wait until it does it more often?

Vader13, is the smog pump the same one as the one stated above? "secondary air injection pump"

xqwizit, do you still hear the sound when you start driving? does it always have the noise now?

Thanks guys. When the noise comes up again, I will check for the source of the noise near the foglights.

Vader13

Mine was making a whizzing noise too.
It was the smog pump thats all I know...

xqwizit

bnz616, yes, I intermittently hear the noise when I'm driving (even on the highway). The noise seems to vary with different throttle pressure. Sometimes I can hear it, sometimes it's not there. It's hard to reproduce but I know it's coming from the driver's side of the car.

IdriveFast

i took my car in for service today for the noise you guys are describing. I hope I dont get my car back tomorrow with them saying "we couldnt find out what was wrong"

MadC32

could be called the smog pump, all I know it's purpose is to lower emissons.

It's really no big deal.. can't cause an engine failure or something. It really just is here to lower the smog emissions.

IdriveFast

well... i got my car back today...and they said they couldnt find out what was wrong! T_T

bnz616

The squealing noise came back again tonite. Was parked outside for about 10 hours....probably around 55 degrees outside. I checked for where the noise was coming from, it wasn't behind the foglight. It came from directly center front, so I popped open the hood and listened to where it was coming from. It sounds like its coming from right under the mb badge on the engine cover. I peeked under there and there are some small pulleys. Does anybody know what the pulleys directly under the engine cover (right under the mb badge on the cover) do? What do they belong to?

I turned off the car for about 30 secs and turned it back on and it went away. I drove home and parked the car inside the garage. The squealing noise apparently came back while I was driving home. I turned off the car again and it went away....don't hear it anymore. It's annoying me because I know I won't be able to replicate the noise for the dealer to hear.

Vadim @ evosport

bnz616: Right under the cover is upper idler pulley. Sometimes it will squeal, mostly when cold. Have the dealer do a cold start. They should be able to hear it.

bnz616

The squeal doesn't come up all the time, which is why I'm thinking the dealer might not hear it and will dismiss the problem. Is this noise normal? and is it even a problem? What is a possible solution?

Thanks.

bnz616

Where is the plug to the secondary air pump located? The sound came up a few times these two days and I think its time to bring it in. It happened even in the afternoon, so it isn't happening necessarily on fresh cold morning starts. If the noise comes back again, I might disconnect the pump to see if it is the pump that's causing the noise. It's loud...reminds me of a screaming kettle. Sometimes goes away if I shut off the car and wait a minute or two before starting it up again.

What happens if I disconnect the pump? How does this secondary air pump / pollution pump work anyways? Will it affect anything if I disconnect it until I get a chance to bring the car in?

BenzoAMGpower

i have a noticalbe whining sound comming from under my hood but it seems that as the sound becomes louder my butt and back get pushed further back into my seat.... :p

bnz616

Haha yeah. But this sound is a nasty squeal/whirl!

360_iti

r u sure it didn't come from your BACK seat ? :p
I've been having the same problem .. I'll take it to the dealer tomorrow.

BenzoAMGpower

oh thats a louder whining, screaming, and moaning noise, last time i diagnosed it, it was my girlfriend and I that caused that :v

alafrance

I had the same thing happen in my 02 C32. I did the same thing, I unplugged the pump, but I did mine over night while my car sat in the garage, then the next day I plugged it back in and it worked fine for a few weeks. Then I took it to the dealership for some other work and I mentioned the problem that I had and they told me it was a bad relay switch on the smog pump (pollution pump, air pump, whatever they want to call it ). The overnight unplug I did may have let the electronics reset because it did work fine after that but the switch did need changing. And yeah, it took the MB mechanic about .5 hr.