The 4 wheel drive on my 1989 isn't working. I assume it's a vacuum line put not sure how to find the leak or fix it. I found one line in the engine compartment that doesn't seem to have anywhere to connect to. It's the blue line and it just ends near the heater core. Could this be the problem? thanks

 

plug it and see what it does, my old xj did the same thing

 

pull it off at the actuator, if my memory is right you can crank it and have vaccuum down there. It could just be off, i picked up a jeep one time cheap cause the 4x4 wasnt working. The hoses on the axle had come off.

 

the blue line isnt supposed to be hooked up to anything, that black thing at the end is a one way check valve, that line is a vent.