Need help fast. Short reverberating sound coming from engine after cold soak start.

[IBrokeDadsCar]

Hi there. My dealer cannot seem to recreate this issue that I hear almost every morning since temperatures have dropped down around freezing. Each morning when I start my vehicle, approximately 6 seconds after startup (right when my automatic climate control kicks in) I am hearing an unusual noise from the engine passenger side compartment, and it doesn't seem to come from the top of the engine. This will ONLY happen on a cold soak start, for instance when I come out and the car has been sitting for awhile in the cold (<40 degrees). If I were to start it, create the sound and immediately turn off the engine, then start the vehicle again right away, it would not re-create the noise. The sound is loud enough to echo throughout a parking garage. Also, it will NOT make the noise if I have turned off my climate control, so I am led to believe something with my climate control hardware is causing something to move in the engine compartment (or excess load on a belt) that would cause this noise. When I push the climate control AUTO button to turn it on while the engine is running, the noise immediately shows, for only a second. Turning the climate control off and then on again will not create the noise. It's a one-shot deal until the car soaks again in the cold, but is very annoying every morning.

My vehicle is an Explorer AWD V8 engine Limited, with 36k miles on it. It is currently at the dealer again (they're honoring Ford's warranty) but they cannot seem to recreate the issue. I have posted two videos of the sound here:

http://www.youtube.com/watch?v=iQTtqdGV6Qw

http://www.youtube.com/user/KeyboardTrouble2?feature=mhum#p/a/u/1/4xKETsgGhpQ

Since it is currently at the dealer I value anyone's input as to what this noise might be. It doesn't sound normal and I'd really like to get it fixed while they're honoring the warranty. It would seem to me that something that turns on in the engine compartment when the climate control turns on, but I don't have the knowledge like some others in here and could use the help. Please let me know if you have an idea what this is.

 

[Bill Kemp]

Just a guess......May be the AC compressor. I dont know why it would make that noise but it is about the only thing under the hood that is effected by the climate control.

 

[swetrid]

It is pretty common occurence on all model lines now adays. It is the ac compressor getting liquid slugged because freon settles in the compressor and that has to pump it out on the first application. It is normal and wont hurt anything. Ford had a bulletin out that says its normal.

 

[IBrokeDadsCar]

It is pretty common occurence on all model lines now adays. It is the ac compressor getting liquid slugged because freon settles in the compressor and that has to pump it out on the first application. It is normal and wont hurt anything. Ford had a bulletin out that says its normal.

This would make the most sense to me, and I appreciate the feedback. Dealership told me they thought i was my aftermarket alarm tied into the starter, but that just doesn't make sense as to why it would only come on with the climate control. I'm going to assume it's normal since the dealer gave it back to me and the info provided here. Glad to finally feel confident about the issue, and thanks guys.