1gmctruckman

Hello, Having a issue for a short time now

The issue is, when pulling long hills at normal throttle (not even necessarily flooring the vehicle) My vacuum slowly drops off untill my ac vents switch to default, I would assume come winter time this will cause 4wd issues as well.

I have replaced the 4wd actuator (torn with trans fluid in it), the vacuum check valve (seemed to have a low pressure leak), and the transfer case vacuum switch (sort of assumed this was the reason my t-case was flooded and trans fluid got in all my vacuum lines).

Some history about when this started:
This HVAC issues did not exist before, but this past weekend I had lost 4wd, Drove it right home and tore it apart, found front axle actuator torn with trans fluid and t-case flooded with trans fluid, so I replaced the actuator, and the vacuum switch on the transfer case. As well as a few of the vacuum lines that looked crappy, I also cleaned out the best I could, the remaining vacuum lines. I also emptied the vacuum canister, which was about 1/2 full with fluid.

Now my question, are the seperate systems, the line to the t-case and the line to the HVAC system suppose to hold constant vacuum or do they bleed down? If I put a gauge on these systems and shut the vehicle off, the vacuum slowly falls off.

With a vacuum gauge after the check valve I maintain 18 in of vac at idle, but at normal driving this starts to fall off. Normal acceleration it falls to around 5 in of vac. Pulling the hill it slowly keeps decreasing until I do not have enough to keep my vents in the selected position.

Should I be looking for a vacuum leak or is it normal for these systems to leak a very little bit?

Any help or ideas are greatly appreciated!

1gmctruckman

Okay, just wanted to check back in. The brand new dorman transfer case vacuum switch was actually leaking more vacuum into the transfer case then the one it replaced. So I ordered a replacement switch from the dealer instead. Took the switch out and plugged it with a cap and vacuum falling off went away, all systems are sealed again.

1gmctruckman

Well it turns out each mode, AC, or defrost is leaking vacuum as well. When I checked before I must of had the selector switch to off.....crap...it seems pulling the dash out is in store for me!