I have read a bunch of stuff try iij ng to figure out what is causing the overheating. It is a f350 470 automatic transmission. I have changed spark plugs wires and adjusted timing to 12 adv. New water pump, 4 thermostats at different temps, fan clutch, temp sending unit, and the radiator is 2 years old. The truck feels like it has tons of power but anytime I drive it it gets warm and bounces the temp gauge from 3/4 of the way and boiling to 1/4 of hot and not boiling. When I have on the gas stays cool but when I let off and coast it will warm up. After I get it home and park it will warm up a bit. Then when I rev it will cool down. I notice when it's running it dont look like any hoses are collapsing but when I shut it off it seems like it is trying to suck from the thermostat to the top of the radiator. And when I take the cap off it sucks air and stops boiling. I don't know what to do next.