Hello,

I have a 2009 Lincoln MKS with the 3.7L in it. Whenever the A/C compressor kicks on there is a putt putt sound like a steam engine. It is proportional to the RPM's/speeds up and slows down with engine speed. I cannot hear it from in the car. It does not come from the compressor itself but sounds like it's coming from the opposite side of the engine on the upper part between the intake manifold or air intake or front valve cover area. Any Ideas, is this common? The A/C works and blows cold and the noise stops when the compressor clutch disengages. I'm trying to figure out how serious this could be. Thanks for the help.

-Travis