I have an 89' F350 bone stock 196k . Rolling along hit a long pull it got hot but cooled out . Next pull it got really hot and wouldn't cool out , got stopped let it cool filled it back up with water , no leaks , no bad stuff . Take off again and running flat ground it's ok but it heats on the slightest hill .........
So in the last 150 miles I've changed the thermostat , lower hose , water pump and lost about 6 gallons of water coolant . With the new water pump it looks like 45 mph and no hills might be a thing ........ I've got 900 miles to go 825 on I40 to get where I'm going .
Is a radiator going to fix it . Could a radiator go from a note temp rise to full blown heat at moderate load in 1000 miles ? Gas typically won't but will a diesel ?