First time here, so I hope I'm in the right forum. 2015 E350: Whenever I turn off the engine, a humming noise is evident that seems to be coming from the engine compartment. Sometimes it lasts a few minutes; other times for over an hour! I've read that some owners actually lock the car and that the noise eventually goes away. I've tried that: It works sometimes. And other times, after the noise has stopped, it comes back after some time has passed. The car has not been started again; the noise comes back on its own. I have spoken with techs at MB and they suggested that I take the vehicle to my dealer. The dealer kept the car for two full days and told me that they did not hear any noise! My wife and I are not crazy....the hum is there. Please, if anyone has found a reason for this hum, please let me know. It just seems impossible to think that MB corporate is not aware of this obvious flaw. Thank you!

 

You're most likely hearing the evaporator fan. It runs for a while to help remove moisture in the A/C system. Many of us have discovered and reported this humming noise; usually soon after buying the car. My year old '14 E350 does it too, though the run time is now much shorter than when it was new. All said, it sounds normal to me.

 

Thank you Sgooter. But...it is NOT a fan noise! It is actually an "electronic" sounding hum. I have had several MBs since the late 80's...I know what a fan sound coming from the engine area sounds like. This is not that sound. It is almost like the sound an old radio or TV made when the sound was off...you could hear the "electrons running around....making a HUM!!" That's what this noise is like! I'm afraid it is causing some kind of damage either to the engine, the battery, etc.

 

I have to agree with sgooter, I have the same sound. I'm sure its a small fan motor Like the ones inside a computer. Sounds like a hum, which in reality it is. Usually goes away after a short amt of time or when i open the door and close it...

 

It has to be the evap fan. It always stops when you open the drivers door. If it stops when you open the door than that is it and the techs should have explained it to you. You need to be in a quiet garage to hear this. I could not imagine listening for this sound in an MB service area. You would need to have superman hearing.

 

I would agree..however there are time when the noise lasts for over an hour. Other times it disappears,, only to return a few minutes later and remains for another prolonged period of time. It DoES NOT stop when the drivers door is opened. I am convinced it is NOT a fan motor. I will invite my service tech to my home so that he can listen to it in my garage!!

 

Do you have the MR FUSION option? Could be the flux capacitor.

 

I am treating this subject seriously! I have no idea what you mean by a "MR FUSION option"! The hum I/we hear is most annoying, especially not knowing what is causing it. The fact that it sometimes lasts for quite a while (up to an hour) and will re-start on its own after being quiet for at least 30 minutes, is puzzling. I have spoken to techs at MB in addition to those at my dealer...all of them are stumped! I can't believe they cannot determine what is causing it. Today, I am inviting my service tech from my dealership to come to my home to witness this problem. Maybe then, my sanity will be vindicated!

 

Vindicated. Sounds like you are having a war with your poor car. The Mr. Fusion is from a movie series way before your time called "Back to the Future" and involved a Delorean. Good luck finding some satisfaction.

 

Is this a standard feature? I always switch the a/c off just before I arrive,
but seems this is not necessary then..?

I never heard this fan though, unless the fans of the LED lights drown it out..?

 

"Back to the Future" before my time???/ LOL....I just didn't put two and two together!! Verrry funny! I spoke with my dealer tech; he wants me to record the sound and bring the car to the dealership and leave it for two or three days....again. I'll let you know wha' hoppens!

 

As mentioned just above your last post, do you have the LED lights? They have multiple fans that definitely make a hum noise to cool the ballasts and move air around the lamps and housing.

 

Yes, we do have the LED lights. I had thought at first that the hum was coming from them...but later decided that I cannot pinpoint from where the sound is coming. Very strange that the hum should re-start after an hour, when the entire car, engine, lights, etc. have cooled down.

 

Now I have to go back and watch Back to the Future again. Will report back on the humming sound from Mr. Fusion and the flux capacitor.

Why don't you raise the hood when you get home so you can better pinpoint and record the sound? The LED light sound seems to come up in more and more threads as it is catching owners off guard.

 

I hear several sounds coming from my car when turned off. Some obvious, some not. I'm fairly certain it is something normal, but since it is under warranty, you might take a line from 2001 A Space Odyssey. Let the part/parts fail, then it will throw a code and you can have the dealer fix it under warranty.. I'm still going with the evap fan. When I was a tech, that was a common compaint people had.

 

Dont drive yourself insane if you arent already....its fans for your sensitive led lights that would otherwise burnout prematurely...something you will have to get used to