Hi all...

2004 late build 3.5 AWD Pac...when the car is warm and I turn the key to "on" (not start) I get a single pop or knock sound from under the hood, this is in addition to the normal 4 second humming sound the engine always makes. I have isolated it to the front of whatever the black metalic thing is under the plastic engine cover, it can easly be felt poping with the bare hand. When the engine is cold it dies not do it.

Any thoughts?

 

ours did the same thing last week in the same spot. Doesn't do it all the time. Seems to be to the right of the alternator.
it sounds likea mechanical pop.

 

check to see if your ac is on. could be clutch engaging. another poster suggested it to me
makes sense, mine does a lot of different things do to the ac being on. cooling fans come on
immediately when ac is on. don't ever come on when it is off.