I have the same problem now with my 1997 ch613, I got an E7 355 and it's pushing coolant to the overflow tank but it's not retrieving it, i notice that when the bottom tank gets full and the fan clutch kicks in, the coolant gets sucked back up to the top tank and that's when it cools normal, but now it's not doing it and it's pushing coolant off the bottom tank cap until the alarm turns on and shut off the truck, it doesn't get hot it's just low on water. I've try almos everything
change water filter, change top tank, change most of the main hoses, new gaskets on air compressor, took off water pump and its good, oil cooler is clean, radiator got clean twice now. What else can I do? We did some test to check head gaskets but we didn't find any carbon monoxide . I can run 100 miles before alarm is on.