My M104 makes a noise at idle which seems to come from the front/top of the engine. All aux stuff like alternator, AC compressor, belt tensioner etc. is working and not making any noise. This engine does not have an air pump.

The engine seems to work like normal, milage is normal, performance as well etc. The noise has been there as long as I've had the car..

Mileage is over 300000 km, that'll be close to 200k miles.

Can anyone help me pinpoint this problem?

Check the link here for a short video of the noise: https://youtu.be/Ia_Nniw0ZL4

__________________
'95 E36T AMG (124.092)
'98 E200T (210.235)
'00 E430 4Matic (210.283)