Geoff Weeks

my bad, sorry, I read it as "I got 6 of these". Age enhanced reading, Sometimes it leads to funny results.

hopefully you got your pictures messed up because that is the same part number you had before, P-2 not P20

Both my air start units came from Manders, also my aluminum air start tank to replace one of the steel ones that rusted. They have some interesting stuff sometimes.

That would be the heavier end of the Loadstar line 1800. Air braked? I think I see an air tank, but could also be for vacuum storage.

I wouldn't try to plug off ports. It is designed to balance the force between the two halves. If you are hell bent on using an E 6 in place of an E-3 then parallel the two sides so both feed the single outlet. If you are trying to go the other way, replacing a 6 with a 3, then there is no way and it would be a red-tag at inspection if you did. Just like single vs tandem master cyl on car brakes.

seeing the paint burned off the tube at the bend behind the compressor, make worry about some "coking" in the discharge line. I would remove and clean or replace to be sure of it. I kept a very close eye on my air system and rarely if ever had a problem. I don't think any of my trucks had a relief before the drier, all had them at the drier.

here it is from the horses mouth (Bendix)

The earlier compressors in the Tru-Flo series, TF500,600, 700 and TF501 I don't think had the provision for a relief the TF 550 I believe does. It is a later compressor. I still have some 500 and 700 models, I'll have to check if I have a 501.

P.S. glad it worked for you. disconnecting the line and running at high speed is kind of a "hail Mary" type situation, may work, but sort of last ditch effort before pulling the compressor.

I don't think the TF501 has that. Replace the elbow from the tube with a T fitting and a pipe to flare adapter and put the relief valve there. Also inspect or replace the copper line. If the head had carbon build up good chance the copper line does also. Be sure to use a high temp relief valve as the outlet temp can be quite hot

Here is a link to the manual, but they barely mention the T brake. Brake manual

They are "obsolete" but I liked them better than the Q's because they held the shoe in position better with the pin and loop on the bottom end. My 1989 had them but it was likely the last year to use them. The "nail and spring" are just there to hold the shoe against the backing plate. There shouldn't be a whole lot of force, just enough to prevent the shoe from "rattling" against the plate when the brakes are released. The above diagram doesn't show two spring on the nail, only one. One is all I have seen also.

I just saw you have spring between the backing plate and the shoe as well as on the shoe to cap side. I have never seen spring on the "inside" the shoe rested on pads on the backing plate, much like a car does. So only one spring on each "nail".

Looks right to me.

these are the type with a pin (loop) at the bottom and a single return spring across the cam end, with "brake nails" mid way that have a spring and a retainer that you compress and make a 1/4 turn correct? I have had problems with the nails/retainers not being right. Other than that, they are like old drum brakes on cars, not much to them. Photo of the problem might help.