Hey guys, I'm still working on my overheating problem and I think the hoses on my heater core might be backwards. I have a 89 f150 4x4 with a 5.8l efi. According to Chilton's manual p. 290 the heater hoses exit the firewall one above the other. It shows the top hose going to the water pump with a "Tee" connection going up to the TB air inlet( flow coming from heater core to water pump) and the bottom hose coming from heater core to a tap entering the manifold ( flow exiting manifold going into heater core). On my truck the hoses are side by side with the hose nearest the fender going to the the manifold and the hose closest to driver side going to water pump. Is this correct and if not would it cause truck to overheat? (it will overheat and boil over under ten minutes. I have a new radiator, 192 degrees stat, extreme duty fan clutch, 60/40 mix coolant to water, and good airflow across rad. Help, I'm stumped.

 

A little further info. When the engine is cold, and I start the truck then walk around raise the hood and feel the heater hoses, they are hot within 30 seconds. But the top rad hose is still cool. with the radiator cap off and engine running water will burp out of radiator slightly. After 3 - 4 minutes water will suddenly flow steady out of radiator and top rad hose gets hot and hard. Heater core hoses will burn your hand by this time.

 

Are you sure you got all the air out when you filled the system? It almost sounds like a big air bubble trapped behind the thermostat in the block; you have to wait for the thermostat to open with the cap off and the engine running to do the final fill - you will get a big drop in coolant level just after the thermostat opens and that allows the air to come to the radiator and get out - recheck every time you drive for the next several days to keep the overflow tank full. Sorry to go thru all this if you did evreything. I wouldn't think the heater hose orientation would cause your problem. If it is not air in system, could be something serious like a headgasket to make it oveheat that fast.
Good luck.