HVAC Vacuum leak, anybody ever track one down?

Nathan Plemons · #1 07-28-2008, 04:35 PM

Slowly but surely my truck is starting to show it's age. Recently the A/C has taken to transferring itself to the floor if I go up a hill without downshifting out of 5th gear. As soon as I top the hill and/or let off the throttle, it comes back to the upper vents.

This sounds like a classic vacuum leak to me. Any opinions on where to start looking? Does this seem like it would be under the hood, or under the dash up near the HVAC controls?

I guess what I really need to know is if this is a particularly common problem, and if so, where's the most common leak?

Thanks!

Nathan Plemons · #2 07-28-2008, 04:57 PM

I should pay more attention. I probably won't get many answers to my braking question if I posted it under my HVAC thread.

timack · #3 07-30-2008, 01:19 AM

http://www.f150online.com/forums/hvac/249376-help-my-moving-vents.html

Nathan Plemons · #4 07-30-2008, 09:15 AM

Thanks!

I easily found the hose white hose in question this morning but it appears to be fine, at least until it disappears into a wiring bundle. All the other vacuum lines look ok too, they're still somewhat flexible and none are obviously broken. I was really hoping to find something under the hood rather than having to rip the whole dash apart. I guess I'll start with a vacuum pump and see if I can pinpoint a leak. I've had trouble with check valves before on other vehicles. Maybe it isn't working right, that would be easy enough.

My Haynes manual seems to be distinctly lacking for a vacuum schematic. Does anybody know of one?