Intermittent, Catastrophic Air Loss, Mechanics Can’t Find

The only experience I’ve had similar to your problem was due to an unloader valve sticking…wouldn’t kick the compressor on. Problem came and went over a couple months.

Maybe worth looking into.

All I got for you!

 

Only thing I ever saw cause the air to plummet and not repeat it was a brake chamber. This was a roll off container truck. So it had an inversion valve that changes things a bit from a tractor. The regular driver had been complaining about it for several weeks. No one could find anything wrong. While I was driving that happened and locked the brakes down. I could here an air leak jumped out and found a brake chamber leaking badly. Then it was out of air and stopped. Got back in the truck. Air was going up released the brakes and drove it back. Got out and checked. It was not leaking.
All I got for you.

 

And your brakes didn't set?

 

If the mechanics haven't done it already i’d check for the leaks by.
1). Chock wheels.
2) release brakes like you are driving off.
3) let system air up to purge and shut down engine.
4) push brake peddle and apply the same amount of air as you did to stop in that scenario and listen and look around for leak. If you don’t have a helper for that part you may need to hold peddle down with a stick of wood or something.

the plummet and not repeat could have been a release valve that got a bad attitude and just stuck open a bit too long or if the system was at cut in pressure right at the time the peddle was pushed it may have sucked that much more air as the compressor unloader was opening at the same exact time. The compressor is open to engine manifold at that time and if manifold pressure dropped at that time i could see it effect the air to the compressor by pulling it away for a brief second.

 

The mechanics at Love's are the best in the world, bar none. If they can't figure it out, you are most likely hosed.

 

I had this happen once on my 359 Pete. It would come and go, and was about to drive me crazy. Finally got where it would happen quite often and figured out. It was the Foot valve.