Have a 1992 c-class rv with a 454 engine. The engine will overheat 5 minutes after running. Temp goes all the way to red during that time. I have change the fan clutch, thermostat, fan and temp. Senders. The return hose from water pump remains cool and the bottom hose is warm during this time. The overflow tank is bubbling/boiling with the radiator cracked open. The fan clutch does not kick-in either. Is the radiator blocked? How do I check. Repair? This just started to happen recently.
First make sure it's really overheating. Touching the top hose and if it's really hot then it may be. Check to make sure you didn't put eht t-stat in upside down. If you suspect the radiator. Then get it hot and shut off engine and feel in different areas. If you feel any hot then cold spots then the rad isn't working right. Also look for loose fins on the sides and bottom as well as green corrosion. You may have a head gasket problem as well. Also have the rad cap checked as it may be bad as well. If you have a thermometer that is either laser type or can stick int he rad and goes to above 200 then see what the temp is. Also your best mix for antifreeze is 50/50 no matter what type.