bmw 128i whining noise

[Majestic128i]

I have a BMW 128i n51 sulev manual and when I start the car and start driving it (cold start) I hear a whining noise, it gets louder if you step on the gas harder. After the car gets warm and I drive it for a while, the whining noise disappears. I only get this noise while driving after a cold start. Does anyone know what the issue might be?

[atomic837]

09 135i manual here.... I've recently noticed a subtle whining that is related to accelerator input.... seems to be louder on a cold start and less noticeable as it warms up. I'm guessing it's a belt or something-related, but am not sure.

I'm at 125k miles and it seems be a recent thing.

Any ideas?

[dtla1]

Belt tensioner is a common issue on these cars, relatively cheap and easy fix. I think it's recommended to replace the belt at the same time.

[Gangplank]

This ^^. Often caused by oil dripping on the belt from a leaking Oil Filter Housing Gasket (OFHG). If you see fluid around that area change the OFHG, belt, tensioner & Pulley.