I have a friend with a 2008 6.4 using coolant there isant any in the oil but he said he has gone through about 2 gallons in the last 7k miles. Any idea where to start ?
Radiator leaking? Pretty common on the 6.4’s. Leave the cap on the degas tank loose and see if the usage lessens or goes away. Also look for coolant “track marks” on the bottom of the radiator.
Radiator, upper and lower hoses, if its stock, the hose to the lower outlet on the horizontal egr cooler, are all common leak spots. There is also the water pump, front covers cavitate fairly often, egr coolers can pop, typically the horizontal one goes first.
I had a small hole in the freeze out plug on bottom of the water pump took forever to find it and like 6.0 said the upper hose is bad to leak especially if it is a 1 gasket design.