Ok my brother is the kind of guy that would rather push a ford than drive a dodge. Well the other day we were mudding at mud fest and it was pretty deep water like may be up to the bottom of the doors in some spots. Well on the way home his truck started to get hot, we figured it was may be low on water well when we checked the water it was full. It will idle forever and never get hot but if you drive it in about 4 miles its hotter than a volcano. He changed the thermis stat and even took it out. He took it out and ran it without the top hose and that proved the water pump is pumping. And now we are thinking it cracked a head some how but before he pulls the heads i wanted yalls opinions to see if yall would have an answer. thanks in advance

 

Is the radiator full of crap blocking air through it? Is the fan clutch good? If it stays locked it will block air through the radiator. Does it steam out the exhaust? Is there water in the oil or oil in the water? Can you pull a compression test on it?

 

It was full of crap the fan clutch is good the fins were full of mud It white smokes out of the exhaust at an idle. There is no water in the oil that we can tell.

 

what year truck is it? also will it overheat if he leave the cap loose?

 

its an 86 i think with the 6.9 with a banks turbo system

 

Does the lower radiator hose have a spring in it? I know gassers sometimes have problems with the lower hose collapsing, not sure if diesels have that problem. Try holding the throttle at cruising rpm's and watch the lower hose.