Geoff Weeks

Our school buses chained up and kept going. I can still "hear" the sound of the 392 and the tire chains. And that was if lived far enough out not to walk (up hill both ways in a snow storm). They did call off school before the chains were needed on the steer tires tho, softies!

Water, unless it has antifreeze mixed in is not from a mechanical defect in the compressor. Oil can pass and get excessive on a well worn compressor, BUT it can also come from too much on time. Look at it this way: your system cycles 23 times more than mine, meaning that 23 time more air, condensate and oil are put into the system then mine does. even my worse truck passes 10 times less than yours is. On mine, the small amount of oil gets separated at the labyrinth passages in the AD-4 base, the moisture gets stripped in the drier bed, both get expelled when the drier purges. Even with an air starter, air wipers, air ride, I never saw any moisture in the wet tank, the air use was such that the air drier could do its job. With yours passing so much air, you are likely going to need to service the air drier when your problem is solved, but no point doing so until the air leaks are addressed. I had a problem with the AD-9's where the drier cartridge would back out of the base and just be rattling around inside the dome. They used a single threaded bolt on the bottom of the cartridge into the aluminum base, heat and vibration would cause them to loosen. enough time on them, the thread in the base would wear and not stay tight. AD-4's have some draw backs but that isn't among them, I switched to them. Spin on filter air driers don't have there internal purge air and must take it from somewhere.

water and oil is more a sign of excessive "on time". Knocking, like piston slap or con rod bearing is a sign of a worn out compressor that is on its way out. You can read what Bendix say in the attached .pdf TF 501.pdf

Well, he did say he ohm'd out the sensor, that implies electronic of some sort.

I would think a 1990 would have a Prestolite Trekstar electronic speedo

electronic speedos came out around 1983 +/-. However my 1992 Marmon came with a cable driven speedo, but fairly sure it was one of the last. When electronic engines and ECM's came around in the early 90's, and then the speedo's became operated on the Can Bus from the ECM. The early electronics had 3, 4 or 5 wires. power + and -, signal and signal ground (two grounds are combined on 3 wire speedos) and then they often have a extra wire for 2 spd axle correction. Most common are 4 wire, + and - and then two wires to the pick-up. Tach is the same but of course no 2 spd axle wire.

"Send us your trash (bags)"!

I have no hard evidence either way, but suspect OEM's design and build some prototype items in house then contract to another company that say, make cyl liners to make them to the OEM specs for production. Pistons may be made by Mahle, a big piston mfg, for the OEM and then make aftermarket pistons to sell. I know with Cummins, if you want the most up to date design, you need to buy OEM but the previous design will show up in the aftermarket. You can get good quality in the aftermarket, and you can get junk, you might even get the same item sold by the OEM with an aftermarket branding. As far as roller bearings, Timken comes out of Asia now, not Canton, OH. Mack likely contracted to one of the big bearing mfg to make their "branded" bearings.

3rd world is where the demand is for older engine parts. They are still running stuff that is considered too old here. Ran into the same problem working on a 30 year old Kubota, Kubota doesn't show any parts in the system, plenty from India and the rest of SE Asia.

Bendix's method of timing the time the compressor is compressing vs off time is the most accurate. It is hard to tell when the compressor starts compressing esp sitting in the driver seat. Timing the time between drier blow-off rolling down the road at a constant highway speed is a good approximation, and easy to hear from the drivers seat on most trucks. You can also watch the pressure gauges. If the go to cut-out pressure and never move, but the drier keeps cycling, the leak is between the compressor and wet tank (inclusive). If one gauge drops to cut-in while the other stays higher, then look at that side of the duel line system. If both drop, (esp if towing a trailer) it could be the trailer that is leaking. All trailers are "single line" brake system that can be fed from either the primary or secondary side of the tractor brakes.

Ahh, that is what you are going to have to find. My best truck, air ride truck, air ride trailer, air wipers, air start, fully loaded on the interstate would go 45 min between blow off of the air drier. My worse truck was around 15-20 min. The differance between the two most likely had to do with the best used nylon air tubing and the other used airquip hose. Every hose, every fitting and valve are potential leaks. Not a fun job tracing them all down. Bendix says 25% duty cycle, meaning the compressor is compressing 25% of the time MAX. (high use is 25% low use is 15% between those two is normal) That is you time the when the compressor starts compressing till when it stops, then time to when it starts again. Put the 1st number of minutes over the 2nd and the result should be less than 0.2. Stop and go driving is going to use more air, but if you compressor is already struggling to keep the system up, it will be running continuously in stop and go traffic. You'll notice that intake pipe is clamped to the rear head to keep it tight to the fittings at each end. Your pictures don't show a tube/pipe anywhere near the head.

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.