I have 2 ISL Cummings in a Crane Carrier Corporation truck 2007 one is fine the other turns the antifreeze black. I have flushed it three times, no fuel smell or oil in it just black. It takes about 2-3 weeks to turn it. I was told electrolysis could be an issue I ran 2 10 gage wires from radiator to engine. the ground strap from engine to frame is good. Looking for any help out there.