I was ordered to deadhead to St Louis yesterday, great, quick payday! Only problem is there were plenty of crews in the hotel, we ended up spending plenty of extra time there before getting ordered to dogcatch or relieve a train leaving the TRRA in Madison Il with power and air issues. Sounded like a troublesome train and it was very contrary to work with. When I relieved to originating engineer after 11 hours on duty he told me that the third engine was red tagged and not to be used in any circumstances, of course it was the newest. The two engines on the headend were BNSF 679 and 783, 2 old warbonnetts still in silver paint. They definitely showed their age. 783 had issues coming out of Madison, everytime the train stopped the engine quit loading amperage to the traction motors. Through a lengthy discussion with mechanical he was able to get it to build power, the process he relayed to me. The lead engine had a faulty Automatic (train brake) valve, everytime you set air it had an excessive amount bypassing and making a horrible racket in the cab. I dealt with these issues for about 4 hours of stopping and going trying to figure out the best way to run this train without further damaging the motors or hardware. The lightbulb finally went off as to a cause of the second unit not loading after stopping. we are taught to almost always use the dynamic braking feature to stop the train and with the bad brake valve the first engineer was surely only using this method. I left the conductor in the seat and i headed back to 783 and turned the dynamic breaker off and had my copilot put the train into dynamic and pack to power. Problem solved! While operating a 9900 ton train with only 1 dynamic and 2 motors under power is not favorable, it is better than operating a 9900 ton train with only 1 operable engine under power. At 12 hours on duty we rolled into Beardstown and a yard crew added an extra engine to get it on to Galesburg. Crisis averted, lol. Good night to all and Happy Railroading!