Howdy all!

I have done a number of searches for my 2003 SD 4x4 PSD and still need help. My ESOF quit working about 2 years ago and I just used the manual hubs and figured I would fix the problem later (Later became now as I am currently unemployed!). About 1 month ago, the AC system started blowing out the vents (on my way to a hot NM antelope hunt!). I know this is a sign of a vacuum leak. I found two leaks under the truck where sagebrush broke the vacuum line between the wheels and pulled 1 line out of the right side and fixed them. Still no AC!

I bought a vacuum tester and found the following:

1: 16-17 in Hg to Canister
2: 16-17 in Hg other side of Canister
3: Vacuum pump never turns off!
4: Tested all vacuum lines to solenoid and they do not leak.
5: put vacuum line to solenoid then turned on 4 whd- Built to 7 in Hg then lost all pressure.
6: put vacuum line to 4 wd system and eliminated solenoid- found 16-17 in Hg at right and left wheels: I was pretty happy that the my line fix worked!

Questions:

1- The vacuum pump pulls 16-17 in Hg but never turns off. What pressure should I have and how long should it take to turn off?

2- Solenoid seems to work but only builds to 7 in Hg before it bled pressure... Ideas?

For now I have blanked off the vacuum line to the 4 wheel drive system and got the AC back but am worried the vacuum pump will go bad soon as it runs full time!

Thanks for your help,

Cory

 

The solenoid only pulses a vacuum pressure to the hubs, it's not constant. I'd guess your leak is either in the vacuum "tank" or the solenoid itself.