New member stupid question. Leak

I just picked up a m931a2 and today for the first time I engaged the front axle . There is a constant air draw sound for as long as I leave it engaged. Not sure if that’s normal or not
Then I un-engaged the front axle , drove for a mile and noticed I’m leaking from the front ABS limiting valve and from somewhere above . Not sure if it’s a coincidence or if that leak was caused by pressurizing the front axle.


Known issues I’ve found

.. the leak I just described
.. abs light goes on and off periodically
.. abs light does not go out before start up
.. the tank selection lever is stuck and cannot be moved from the passenger side fuel tank

Any suggestions would be appreciated

Not on the same system. Replace the Q2 valve. This is the front valve in front of the front axle. That is only for equal pressure to the front brakes. Not the ABS.

When you engaged the front axle your leak is either on the line going to, the linear valve at the linkage on the transfer case or the linear valve to front axle Engagement line after if.

With the truck in low range and the axle switch off see if you have the same leak. If you do then it is in the linear valve or the short line from the linear valve to the front axle Engagement on the rear of the transfer case behind the driveline brake drum

If your transfer case is leaking it may be bypassing the interlock solenoid and pressurizing the transfer case. You can sometimes hear large air escaping it just varies on how the air lines are hooked up. Correctly.or not

No, constant air draw is not normal, you should hear a brief ssspt, as you select in or out. Sure it's not the CTIS moving air? I don't recall it doing that but then I'm getting old and haven't driven them a lot lately.. Try using a pair of adjustable pliers for leverage to turn the tank selector. I know on my wrecker it was hard to move the selector switch. Probably that one too. Should be easy to find where it's leaking. Get the truck up to full pressure, shut it off. Then select in. Hunt for the sound of leaking if it wasn't the ctis moving air.