Air Brakes on M923 Locking up

Fulton Volunteer Fire Dept has M923 that we have coverted into a brush truck. I have posted before about airbrakes locking up and have not been able to get them fixed. My first question is, does anyone on here live in the Corpus Christi area? Second does anyone have anymore suggestions on what could be causing the brakes to lock down completly when air is applied to system whether the park brake is on or not? We are desparate and need help the truck has been out of service for a month now. Thanks for your help!!

Bring it to a big rig shop. It's all basically standard big rig braking components.

Check to make sure the glad hand dummy coupling on the front passenger side has a vent. Otherwise, the air brakes on the 900 series should be able to be repaired at any heavy duty truck shop. The system is not military-special.

wedge type...

They are wedge type brakes. If the wedge is sticky/rusted/gummy from a lack of service then it will apply but not release. Just a possibility.

Justin Wehring
979 997 3112

Will try and get back to you !! thanks for input