ml320 whinning sound- cold start???
 

Help!!!2003 ML 320 --When I first start the auto and if it's cold- 30 degrees or lower it make a high pitched whinning sound that only last a few seconds up to a few minutes then goes away. Makes the sound with or with out the heater turned on. Sound seems to be coming from dashboard in front of driverside, maybe in front of firewall --don't know.

Is it road speed dependent or RPM depenent?

Car is just idling, in park. doesn't make a difference if i rev up rpm's. the sound also stops all at once. It's also high pitched. Thanks for any ideas!!!!
When I took in ---course it didn't make the sound but was warm outside.

Is it the AIR (Air injection reaction) pump used to reduce cold start emmissions? If so, it makes some noise when it runs which is normal.

Don't know?? This is a new sound and not normal ---the colder it is the louder the whinning sound. Can this pump start to fail and become louder? Or any other ideas? With hood up --still hard to pin point where the sound comes from---but seems to be on the drivers side.

Could it be a bearing on one of your accessory drive pulleys?

UPDATE---after listening a couple of times You can hear some type of motor that shuts down after the engine idles down This is after first starting the engine when cold. I believe the problem is in that motor/pump/what ever that is???