Re: NNG Westinghouse Air Brake M24C .

First - you picked the wrong forum to post your question, as this is primarily steam or narrow gauge. There was a 24ET for steam, but it was extremely rare. The "standard" brake valve for diesels in this era was 14EL for small switchers, or 6BL (6SL in Canada and exports). 24RL was an extra cost option for "road" units, and is the successor to the 8ET/8EL. I'm not aware of any 24RL being applied to narrow gauge, though it was possible.

Second - 24RL isn't a bad brake to run, but there are so many factory variations and subsequent modifications that it is impossible to just say how it works. If it is actually an M24C valve, then it is an entirely different type of brake valve used for transit and maybe some early streamliners.

Third - If you don't have any air brake experience, don't try to fix it yourself. These vavles are well worn and being ring and piston need to be tested with the proper test bench for excess ring leakage and proper operation. You can try Ralph at Multi Service Supply http://www.multiservicesupply.com/ for a repair and return. They are usually pretty decent at repairs of older valves, but it will cost you.

Best source for manuals is eBay. Be sure what you are looking for. M24C is somewhat rare, if it is a D24MC (diesel) then you need a later 24RL manual.