Buzzing/Humming Sound Under Hood

[335dye]

UPDATE: Water Pump

I am looking for a little bit of help in diagnosing this noise. When the A/C or heater is blowing, there is a loud buzzing noise coming from under the hood. It seems to be almost dead center on the front of the motor, right behind the radiator. It only makes the noise with air blowing. It goes away when you turn the air off. I did notice that if the heat or air is blowing and you shut the car off, the noise lasts about 5 more seconds. I did take a video and will try to upload it for reference. Thanks for any advice or insight before I end up paying the dealer to diagnose it.

[335dye]

Originally Posted by 335dye

I am looking for a little bit of help in diagnosing this noise. When the A/C or heater is blowing, there is a loud buzzing noise coming from under the hood. It seems to be almost dead center on the front of the motor, right behind the radiator. It only makes the noise with air blowing. It goes away when you turn the air off. I did notice that if the heat or air is blowing and you shut the car off, the noise lasts about 5 more seconds. I did take a video and will try to upload it for reference. Thanks for any advice or insight before I end up paying the dealer to diagnose it.

Video link

[argento]

Maybe something caught in the cooling fan and the blades hitting the object? I caught a license plate once in my E36M3...now that was loud.

[335dye]

Originally Posted by argento

Maybe something caught in the cooling fan and the blades hitting the object? I caught a license plate once in my E36M3...now that was loud.

I will check that out. Last week it seemed like it only made that noise when it was blowing full blast. Now it doesn't matter what setting it is on.

[Dawgz]

Originally Posted by 335dye

I am looking for a little bit of help in diagnosing this noise. When the A/C or heater is blowing, there is a loud buzzing noise coming from under the hood. It seems to be almost dead center on the front of the motor, right behind the radiator. It only makes the noise with air blowing. It goes away when you turn the air off. I did notice that if the heat or air is blowing and you shut the car off, the noise lasts about 5 more seconds. I did take a video and will try to upload it for reference. Thanks for any advice or insight before I end up paying the dealer to diagnose it.

There is a auxiliary pump in that area...that might be the culprit.

• There's an aux pump for the turbos.
• One for the intercoolers
• And a third for the main system/and heater core.


Yours sounds like it's the auxiliary pump for the main system (not the belt driven one on the block). That one is in the driver side front bumper area.

[335dye]

After a little more troubleshooting, I tried running the A/C and the heat and the noise happens in both settings. I noticed that if I start with the temperature at 60 degrees the noise is not present. But as I raise the temperature, a degree at a time, the noise starts and gets louder the higher the temperature.

[335dye]

Another Video. After I let the noise run for probably 5 minutes while waiting for radiator fan to kick on, I noticed the noise and the air would start to get loud and then quiet. I also noticed that no air was actually blowing out of the vents except for the rear seats and the windshield defrosting vents.

[335dye]

Just an update… ended being the water pump. I dropped it off at the dealer and he called saying it was the water pump and that it was covered under warranty. I guess in relation to the class action settlement. Luckily saved a nice chunk of change. Thanks for all of the input.