Locked up coil, possibly due to air

Heatsink

I got this large air handler that that a few times a day locks up and stops working.
others before me have replaced the trap (f&T) as well as the strainer.
after a few days fiddling with it, I got the system to work continuously (I hope) by cracking loose the plug on the steam side of the trap. So, after making this discovery I installed 2 new air vents one of them I put in place of the plug I cracked open. it stopped working again. the traps worked great when there was a large amount of air during start up.
I will remove the air vent I installed on the trap and leave the plug cracked again just to make sure.

Any thoughts?
By the way, Dan, I love your book. just started reading it yesterday.

JStar

That looks like it should work. Is the return main hot? Maybe there is another bad trap in the system that is equalizing the supply and return pressure in the coil.

What pressure is the system operating at? Cut-in and Cut-out.