Yellow knob not staying pushed in

Tractor protection valve? That’s my only guess.

 

I don’t recommend it but as a stop gap to replacement, on some models of brake release valves it is possible to replace a worn o-ring to solve the not staying in problem. (Was a former employer’s solution to hitting a bump and the brake setting while driving)

 

Did you get this sorted? My yellow knobe won't push in due to have air pressure behind it.

It's quite hard to push in and won't stay pushed in because of high air pressure behind it, wondering if it's the yellow brake valve, or if something else could be back feeding into the system

 

Great to see a thread starter respond. So many threads like this go unanswered after a length of time, frustrating when searching for an issue, finding several threads on the topic without answer or resolution. Kudos to you sir.

 

Are all Mv3 valve ls the same? They are aren't they?