Geoff Weeks

You need to look at the whole truck. Ready to roll (brakes off) engine at speed. I bet that 2-3 min drops to less than a min at 1800 rpm.

Not exactly, What they show is a tube that is butted up at each end, then a short piece of hose that seals the two together The amount of exposed hose to the pressure is minimal, not the same as your pictures where there is a long section of hose. Still I would use silicone Radiator hose (rigid hose) to make the joint. You also have a clearance issue with another hose which will rub through the heater hose. New piping, new correct hose. Any compressor will pass oil if its duty cycle is high. A brand new one (not rebuilt) will. So 1st assess the condition of the air system before looking at replacing the compressor. There have been people on this board who have replaced compressors more than once with no gain, because the compressor is always loaded. Time your compressor cycles going down the highway, if the compressor doesn't go 15 min between cycles, you have work to do.

I always used Interstate-Mcbee for Cummins but they have nothing for older Mack. I tried a few PAI gauges, I think IHC an Mack used the same, anyway, The PAI were crap, I ended up taking them apart and only using the rear housing, re installing the OEM in the housing. Took a little work, but worth it in the end. I think I tried a few door latches that were PAI also. I hope their engine parts are better.

Heater hose can only be used if the intake of the compressor is connected to the trucks air cleaner (non pressurized). For those connected to the intake (pressurized on a turbo engine) a hose rated for pressure and temp needs to be used. I had some thick multi braid hose that "looked" like heater hose at a glance that worked well. rated for 300 psi and high temp. Where it has to go around the head, tubing with short connector hose would be best. Steel or aluminum tube bent to fit with a bead to hold the hose at each end. That way, no chance of "kinking" the hose.

You got it backwards, the compressor intake is being boosted from the engine.

I looked at it like this: Eaton made close ratio main box with repeatable shift pattern, wide ratio range box. Spicer made wide ratio main box with close ratio splitters, with a non repeat shift pattern What did Meritor bring to the table that was better or different?

Page 116 shows the isolator, just like Eaton. Meritor parts

There are likely 2000 Eaton's for every 1 Meritor. For parts alone, your better off with what everybody else has. Neighbor had one, I don't know what the problem was but he complained a lot about it. Both are a box of gears, and put together much the same way. Look at the stick right above where it goes into the transmission for an isolator bushing.

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.

If the unloader is stuck, it holds the intake valves open, not the exhaust, so it would not leak back from the tanks when the truck is turned off. It does sound like the exhaust valves are leaking . I would likely remove the outlet fitting and run the truck a max rpm and try and "blow out" any debris that might be keeping the valves from closing. Doing this will pass the max amount of air through the valves. Anything else will require pulling the compressor and/or head.

What little I can make out it is a TF-501 Bendix. One of the most common for its day.