Cruise Control Vacuum Pump noise

[DaveHess]

On my 2003 "555" with 48RE with the cruise control engaged, I get a hum that comes and goes from the left dash area of the cab. I found the vacuum pump on the left fenderwell under the hood and was wondering if that is correct operation to hear that occassionally. It's not constant but comes and goes. The cruise works as advertised. Any ideas?

 

[Bill Stockard]

Yep, it cycles off and on as needed to keep the vacuum constant. When you starting your truck after it's been setting a while, you'll hear the vacuum pump running when you first turn on the ignition switch. It eventually cycles off if you leave the switch on and don't start the engine unless you have a vacuum leak.



Bill

 

[DaveHess]

Thanks Bill. Just another one of those unanswered dealership questions. Actually, the dealer here is terrific but the service department leaves a whole lot to the imagination. I kind of figured since it was working as advertised I shouldn't worry. I do notice when I have a tail wind, and we get a lot of wind up here, I'll get a "seat of the pants" surge with the cruise on. RPM and MPH remain constant just that slight feeling of a surge. Thanks again for your reply.