When I first start up my truck, every 11 seconds (I counted, haha) I hear a hiss. I sounds like its coming from the bottom of the truck, on the right side.. I just can't pinpoint it!

When I put it in drive and start driving, the hissing stops.. If I stop the truck, you still don't hear it..

What could it be??

Thanks!!

John-Robert

 

Sounds like condensation dripping from somewhere onto your downpipe or cats... After It runs it would probably be too hot to hear the hiss anymore since it would evap right away.... Do you have your ac on when you start it up???