Bendix brake valve question

[biscuits and gravy]

Oh, yeah... That looks like that can turn into a little nightmare and foul language if that valve starts malfunctioning.

That's weird how they have a black plastic T valve and another brass metal T valve under the port marked DEL.

I think I'd replace those 2 T valves also if I had to replace that main valve above it too. That way you don't have to go back later and trouble shoot those two little ones.

I was told in the past that Bendix has free online training courses (video) for anyone who wants to watch them. Covering brakes and air systems.

If you don't pin point the culprit soon, maybe one of those videos will cover that valve in your photo.