Low air pressure while driving on freeway!?

Check your blue return line as well as see if you hear an air leak outside your truck.


Do you hear air escaping by the red and yellow knobs?

 

Might need to get the governer checked too.

 

That is a pretty nasty leak. Find a safe parking place to try and locate the leak. With one parking brake set at a time walk around the truck with the engine off a listen for leaks. After that sit in the truck and release both and watch the pressure while you get on the service brakes. You shouldn’t see more than a 4 psi drop in a minute. Unless it is a loose coupling you can solve, get roadside to fix it or take it to the nearest truckstop if safe enough to do so.

 

If you were able to build air then the compressor is good. And the tanks would hold air. That leaves hoses and connections everywhere else.

Grab a windex and a rag go around it all with the air built up engine off and see if you can hear and catch leaks.

Sometimes the leaks would be inside the brake chamber itself. It's not always obvious. If you did find Mr Bubbles showing leak, there is a possibility that you can use a vice grip to loop it off and lock it temporarily until you get to a shop.

 

Probably a brake chamber. Keep a set of vice grips to pinch line and a wrench to back brake off, in case next time you’re too far or the leak is worse. Keeps from getting stranded, still Legal also unless on steer

 

Are you in a cold area? Tues I had the same basic issue. Truck lost pressure for a moment, but I was going slow enough to hear the trailer valve pop. Only took a minute or so to equalize the pressure.
As it only happened that time, I'm guessing a small chunk of ice finally worked it's way out and allowed the trailer tanks to fill.

 

My trailer brakes grabbed very hard Yesterday when applied normally. Hopefully just the cold weather. Very strange