‘84 Pete 359 Park brakes won’t release

Ok, this is an ‘84 Pete 359 with an ‘18 Pete air ride cutoff. The cutoff has abs but the electric side of it isn’t hooked up but valves are still in place. So, truck has been doing fine but applied park brakes yesterday evening, while idling and noticed the park brake knob in the cab felt kinda soft and started bypassing a little air. Got out and the rear brake valve, over the rear differential, was bypassing air from the bottom. I put the brake back on, thinking I blew a pancake. Turned one park brake loose at a time, with park brake released and air out each line(all four have park brakes). So, I think all my brakes are good. Changed the rear valve and the new one is doing the same thing so, it’s not the rear valve. The rear valve shares the small orange line with the front valve. It runs into into the front valve at the top. The black line on top the rear valve, in the first pic, runs up the frame towards the cab. Where to look now? Here’s a pic of the valves.

 

I removed the orange line from the front drive axle valve(bottom pic) and air was coming directly from valve. When I did so, no air was bypassing from the rear valve. As soon as I attached the orange line, air began bypassing at the rear valve.

 

I think I’ve got a plug that’ll fit the park brake line, if I take it loose at the can. I guess I can go that route as well?

 

When I loosen the service line from the chamber, with park brake released, should I be getting air from the chamber or the line, if the chamber is good?

 

Well, I’ve done checked the parking side, is it still necessary to check the service side, the same way to determine if the chambers are good?

 

When I removed the park brake lines individually, I was checking for air coming from the chamber but nothing on any of them, only air from the park brake line.