ML320 Engine Whining/buzzing
 

Hello,

Hood open, key in position 2 (just before cranking), a buzzing, whining sound comes from the engine. Looks to be coming from an area left of the CPS. Also, there is a water pump (electric) that used to work all the time but now it doesn't This water pump is near the battery compartment. Any ideas?

Thanks in advance.

Pump
 

The auxiliary pump is supposed to run approximately 5 minutes after the engine/ignition are turned off. It's easy to replace. It is called the auxiliary pump.

Is your ebox fan working (fan is located directly under the fuse box under the hood and is designed to cool the critical electronic inside that fuse box? It should be running whenever the engine is running and if recall correctly, even after the engine is shut off.