M1083 air brake issue question

Suprman · Feb 27, 2016

Swapped just about everything. The schematic makes it a bit easier to deal with. Had to find it on the net I didnt have that TM. Confusing as heck though. I couldnt find a specific flow chart for troubleshooting my issue though. Looking at the schematic I dont think the treadle valve can be my issue though.

Suprman · Feb 27, 2016

So I tried the rear gladhands and they don't work properly. With trailer and brake valve in I don't get service air in the rear when braking. There is a tm troubleshooting action for this issue. Started following the flow chart but ran out of time. I have one more air line to check Monday if air is present then replace tractor valve if not I move on to the inversion valve. Good thing I have parts trucks.

tburk49760 · Feb 28, 2016

When you get this all sorted, please come fix mine... When I pull my air brake type trailer, it takes forever for the maxis to release. The service brakes work fine though...

Suprman · Feb 28, 2016

There is a tm flowchart for low rear gladhand flow. I am leaning towards the tractor valve. Which can be rebuilt. I have a spare I would swap in and then play with the old one.

Oxyacetylene · Feb 29, 2016

If you want to check the tractor protection valve, before you take the whole thing off, I would check the one rubber diaphragm that is located closest to the crimped on vent cap. There are just 4 screws holding that plate on and you can do that without taking the valve off the truck. On my truck that particular diaphragm was the only bad part, but then again my issue was a little different. I was losing air pressure through that crimped on vent cap when pressing the service brakes. If you take the valve off and decide to rebuild it, in case this helps: http://www.steelsoldiers.com/showthread.php?140345-Air-Brake-Info-and-Troubleshooting

Suprman · Feb 29, 2016

The crimped vent cap on the cover piece over the front service brake gladhand?

Oxyacetylene · Feb 29, 2016

no, sorry that sounded confusing. The tractor protection valve itself has one of those crimped on vent caps. It's the same style cap like is crimped on the front gladhand covers. On my truck I was losing air out of that vent cap when applying the brakes. It also helps isolate the air leaks if you let the air pressure build up and then shut the engine off. Have someone apply the brakes while you walk/crawl around listening for the leaks. That's how I found the vent cap issue.

Suprman · Feb 29, 2016

I followed the tm troubleshooting. According to the tm my results show a good tractor valve.

lmtvjunky · Mar 4, 2016

I've had the same problem Will, it was a small hole in a diaphram in a check valve up front, took me 2 days to find it and replaced a lot of stuff doing so. Not saying you might have the same issue, just your symptoms are identical to mine. Good luck, I'll help you by spirit *_*

Suprman · Mar 4, 2016

I swapped all 3 with ones from my parts truck but I wonder if they could be bad also. I have new ones on order.
Will

lmtvjunky · Mar 4, 2016

I had to take them apart to find the problem, small hole dead center, also there a ton of rust and soot crap in everything, lines valves, etc, these trucks are aging quick when sitting, not to mention anything with air systems have continous moisture issues

Suprman · Mar 11, 2016

Got it finally!!! 2 air lines under the cab were switched. I compared each line one at a time to a functional truck seeing where each went to and from.

Rmtaunton · Apr 8, 2019

Do you remember which two I have the same issue and all valves are new

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Suprman · Apr 8, 2019

I think it was 2 lines that went from the cab pass thru to the 3 valves under the drivers area.

SausageGuy · May 20, 2019

I just replaced air dryer with a modern one from MME and now mine is doing this exact thing. I don't think that is relevent but made it easier to use truck air to break down a tire.

Alg1288 · Nov 25, 2019

Hi guys, I have a 2012 m1083a I'm working on wit has the same issue. Would the location of the check valves be different? Been looking near the washer tank and can't seem to find any.

Suprman · Nov 25, 2019

The check valves are under the cab

Alg1288 · Nov 25, 2019

Would you happen to have a pic?

Andyrv6av8r · Nov 25, 2019

Alg1288 said:
Would you happen to have a pic?

Tilt the cab, look on the left inside, underneath above the steering box; 3 check valves there.

Alg1288 · Nov 25, 2019

Checked everywhere near the left side where steering box. Can't seem to find it. Could it be that the 2012 configuration is different?

M1083 air brake issue question

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