My 2007 Suburban makes a "kerplunk" noise when I start it first thing in the morning. It doesn't make it at other starting times - only when it's been left off overnight. The noise is loud and felt (like the whole engine is letting down so to speak). The noise occurs right when starting and I haven't even put it into gear yet.


The dealership has it now and has heard the noise for the last 3 mornings but can't figure it out. The noise is only for a split second and then it's done.


Car is in shop for another issue which I don't think is related. It has been shaking when you go over 70 mph but they rotated the tires and although they haven't gotten it out for a test drive, believe that will take care of the shaking problem.


Anyone have a clue on this?

 

Welcome to the forum...
I can think of lots of ideas if it did it at every start but to do it only once when its cold makes it a bit more of a challenge...
The first one that comes to mind is the slugging of Freon in the a/c compressor