So apparently I have a vacumn leak cause when i turn on 4x4 sometimes it wont come on right away or the a/c will start coming out different vents and stuff. This doesnt happen often though. I hear it is hard to trace one but how would you go about doing it anyways?

 

Isolate/plug the various vacuum lines until the system starts behaving correctly. The ESOF 4x4 system is fed by the vac pump on the passenger fender well. From there it goes to a solenoid valve that is activated by the 4x4 switch. Out of the solenoid it goes to a "T" that feeds each of hubs. Assuming the Vac pump isn't running all the time, you can assume the solenoid is fine. The leak is usually in one or both of the hubs. There is a chance it is on HVAC side of the system, but that is rare.

Start by plugging the line feeding the solenoid. Let the vac system pump down and stop. Start the truck and see that the HVAC works correctly. This will verify that the leak is on the hub side of the system.

Plug the line on the back side of sloenoid and repeat. This will verify the solenoid is good.

Follow the line from the solenoid to the "T" and repeat for each leg of the "T" until you find which one (or both) make the HVAC go bad.

You can also put a vacuum pump and gage on the vac nipple on the inside of the wheel and check that the hub assy can hold vacuum.

Various fixes requiring new o-rings and such, or you can purchase a set of WARN manual hubs and never have to wonder if the 4x4 is locked or not.

 

A vacuum/pressure pump like a Mityvac can be a very helpful tool. I bought one to diagnose a vac leak in my old 99 and found it within a minute after receiving the tool (mine happened to be the passenger side ESOF seal). Start testing lines until you find the one that won't hold vacuum, then trace where it goes.

 

Alright cool ill look into doing this when i get some time.