Release of air RH front of engine

[Bigusdickus]

Some help please

My 1998 SOHC explorer makes a sound like a compressor, Fairly loud 'Chuff' unloading, the front of engine looking from the front, near the EGR valve?. Any idea as to what this is.

Thanks Dick

 

[Bills98Explorer]

My 98 does this to.But only when the a/c has been run,and only after I shut the engine off.Done this since I bought it almost 5 years ago.I call it normal.