M1088A1 - All Service Brakes will not release

[Tga]

Break down:
120 PSI in both front and rear tanks
Air temp - 27 degree F
Engine at operating temp
Park brake released - regular driving.

No leaks in the Air System

The event:
Normal driving conditions - 30 mph, coming up to a Stop sign, apply the brakes to slow vehicle, release the brake pedal to allow vehicle to roll a little further before actually applying the brakes to come to a complete stop.

At the point that I released the brake pedal, I could tell right away that the brakes had not released, the sound you normally hear when you release the brake pedal sounded soft, almost whisper like compared to the norm. I've looked at the TM, to no help at all, any thoughts?

Sometimes when you have a diaphragm (pancake) going out in a brake chamber you will get a slow release of the service brakes after application. It's sometimes hard to tell while you're driving or engine running because the air leak only occurs when you activate the service brakes. Have someone stand at rear of truck while you apply the service brake and listen for an air leak while applied. If not that, there should be a purge valve to release the air pressure. that may be sticking. Not sure of its location on the LMTV series but should be able to locate via tech manual.

 

[Suprman]

The service brakes have a quick release valve its behind the front bumper more to the drivers side. Try cleaning that out. The tm has troubleshooting steps for the brakes dont release issue its not uncommon.