engine hums at idle

My wife,s engine has a loud hum that can be heard at idle . It is a very pure tone that stays at the same pitch even if the engine is reved. It seems to come from the passenger side of the engine compartment . Does anyone have any ideas? Could it be some type of intake air management or polution control valve that is stuck?

thanks , tom

Yes this is known as knocking, very common with subarus. It happens with cold start ups or just not turning you car on for a while. It's not going to blow up, just trying to warm up a little.

AS for the passanger 's side of the car, that could be from a lot of things. Take it to the dealer and have them check it out.

Great seection on buying a subie. :)

For a Subaru genius, you sure misdiagnose things.

For a Subaru genius, you sure misdiagnose things.

^^^ ?
Ok, the guy asked a question about his wife's car and all you say is subaru genius can't figure anythings out? :disappoin Now you pissed him off by changing the subject like now, and he's just trying to get a question answsed. PM me if you wanna rip on my willing'ness to help, or atleast put somthing of use for him.

All I am saying is you're confusing a 'hum' and engine knock.

A hum like say, a power steering pump.

I apologise if you have such a delicate ego.