There is a device that looks to be a small vacuum pump that sits in the engine compartment, on the driver's side, on top of the fuse box. It has one electrical connection and is attached to several small hoses that appear to be vacuum hoses. This has always made a sound when the ignition is turned to the first position and lasts 7 - 10 seconds. Lately it has been coming on about every 5 minutes, even while driving. I had not noticed this happening this frequently (or at all) before, and believe this is something new.

Is this part of the vacuum system, and what is its purpose? Should this "pump" be coming on this frequently? Could I have a leak in my vacuum system?

For reference, it's an '08 F-350 Crew Cab diesel that I've had since April. I've got a little over 12,000 miles on it now.

Thanks for any advice!

 

Zeplik,

Sounds like you have a vacuum leak. Check all hoses and connections for leaks. Does your A/C-Heater vents select properly or defualt to defrost mode?

 

Well here's what it turned out to be.

I noticed that in tight right hand turns the truck felt like the front hubs were locked, but I was not in 4wd. So I cycled the SOF a couple times, and ech time the vacuum pump came on. Then made sure my hubs were completely disengaged by turnning the front wheel drive shaft by hand. Voila! The pump no longer comes on consistently and in fact it seems the vacuum can hold over night as I no longer get the pump turning on every time I start the truck.

My best guess is that one (or both) of the auto lock hubs was in a "halfway" position where for what ever reason, the hub was losing vacuum. After a couple of cycles it settled into its proper position and now there is no more leak by.

Anyone seen anything like this?

Thanks.