Question Vacuum Problem

[shhorn68]

I have an 04 F350 4x4. When I put it in 4x4, while running the A/C, the air blows from the defrost vents for a few minutes before returning to the vents. I know this indicates a vacuum problem and I have chacked the lines behind the glove box. I cannot find a problem there so I am looking for some advice before taking it to the shop.

 

[Crumm]

I would check for leaks in the vacuum lines that run to the front hubs.

 

[Zookie400]

+1

they always rot out.