Periodic humming noise

[AustinRunner]

I have begun to hear a periodic humming noise while highway driving. It lasts for a few seconds and cycles on and off with about a 10 second interval. I have determined that the noise is coming from a device mounted on the passenger sidewall in the engine compartment behind the battery. I think this device is vacuum related and the humming noise is present when it is 'on'. A similar (perhaps identical) noise is heard during the ignition start process. Any help nailing down this problem will be much appreciated. Thanks, Randy

 

[roperteacher]

I had a similar noise on my 06 and it ended up being an AC compressor. If you hold your ear to the front of the COndensor it is real loud.

 

[rbattelle]

I was going to suggest the A/C compressor too.

What makes you think it's related to vacuum? What vacuum pump are you running? And where did you mount it?

Ryan

 

[AustinRunner]

The noise-producing part is indeed a vacuum pump (mounted on sidewall behind passenger side battery). It apparently interfaces with both the AC system and cruise control. I likely have a leak in a vacuum hose that needs to be traced and replaced. BTW, my ride is a 2003 2500 4x4 QC 48RE. This info was not featured in my earlier notes. Sorry. Following up on your collective replies, I'm going to start my search on the AC Compressor side. Thanks.