NHC250 Air compressor replacement

So the air compressor on my m931 is barely pumping air. I tried replacing the head gasket on compressor and didn't make a difference. So now I'm planning to swap the compressor off my m925a1 with a blown motor onto the m931.

I have been looking through the tm's and haven't had any luck finding how to remove the compressor. Anyone have the procedure to remove and reinstall the compressor.

1st, you should see if there is a leak you can't hear. Pressurise the system with the engine not running and see if it leaks. if no leaks, next put air into the system through the discharge line and see if it airs fast, if not, you could have an obstruction. Does the truck have an air dryer? if so, bypass it and see if that makes a difference. The governor could be an issue also, kinda rare though. Remove the discharge line from the comp and hold a piece of paper in front of the fitting, throttle the engine and see if there is a mess of oil sprayed onto he paper. If not, the compressor itself is good, not pumping oil. Your issue is most likely the unloader in the compressor head. Much easier to repair than replace the complete compressor. It takes like an hour to fix it.

Thanks for the tip about the unloader. Took me about 20 mins and now she builds air in no time.

Replaced mine on the NHC250. TM is 9-2320-272-24-2 Starts on page 898 (4-31). Compressor replacement number is a 3018543X. Can be found on ebay as well. Truckpro had mine. Always replace the plastic spider gear on the injection pump side Cummins # 3046200. I do a lot more crap than I probably need to. I have bad ADHD.





https://youtu.be/rbhtKXIgDzI

Nice video thanks! I do have a question about the output hose on the compressor, is it going to be able to take the heat form the compressor? I know on my trucks the copper output line gets very hot when the compressor is running.

M35A2-AZ said:

Nice video thanks! I do have a question about the output hose on the compressor, is it going to be able to take the heat form the compressor? I know on my trucks the copper output line gets very hot when the compressor is running.

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293-6 parker line is rated to 302 degrees. I havent checked the temps yet but i dont think it gets that hot


Also after the copper line it goes into cotton jacket line before the hard plastic line
Sent from my SM-G935P using Tapatalk

Ok, Let us know how it does.

154 degrees at Idle all the way to max pressure after warm up. 187 max temp at 1600rpms for 2mins continuous. This high temp may drop due to air intake at highway speed though since it does draw its supply air from the intake. This is at the fitting on the compressor.

Thanks! that is good to know you can use that type of hose.

M35A2-AZ said:

Thanks! that is good to know you can use that type of hose.

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Like at the end of my video. All my brake chamber hoses are #6s or #8s as well along with some other lines on the truck. so if something does fail that is vital you can always remove a hose from somewhere else and add it in. I am not fond of that plastic air line crap, but I did replace mine from the front to the air dryer blow valve just cause at 10ft it would have been pricey for hydraulic @ 3/8" hose.

Will bump this with a little parts information and update video on that pesky backside bolt.

Stock unit at 13.2cfm part # 3018543X
Upgraded unit Truflow 550 2 cylinder compressor is 107506x.

They are both around the same price

https://youtu.be/j945HrW9IC8

Fuel lines can be an issue if going the twin cylinder compressor, the pump is pushed back an inch or so and the bottom support is different due to the pump being back farther. Navistar used the Bendix Truflow for a long time, so, if you went that way, and could find a corn binder in a junk yard, the pieces parts could be got pretty cheap.