I just cannot figure out this problem: The temperature outside is -4 fahrenheit and my truck is overheating in park idling!! The engine is a new 502 with -69 ovalport closed chamber heads and was installed 1 year ago. The heads were checked before installing. The overheating problem started when I drove through muddy waters (not the band). Because the old radiator had a minor leak I installed a new aluminium radiator (Allstar All30016 19"x31"). There is not room for a mechanical fan so I used an electric fan with a shroud, just as I used with the old radiator. The thermostat is 180degree and the water is sirculating, but not only does the upper hose get hot, so does the radiator and the lower (return) hose!! The ignition may be a little off but there was not a problem like this with the old 4 rowe radiator, the new is 2 rowe (wide rowes). There is no bubbles in the water when the cap is off and engine running. Yesterday, for example, (-4 temperature) I went for a test drive. At 180 the thermostat opened and I drove maybe half an mile at 20 mph (2000rpm). The temperature was 186. I put it in low4wd and drove with maybe 1000-1500rpm and the temp slowly rose to 196. Tried to drive a little faster with 2000rpm and it still rose to 209. Got back to the road and with a speed of maybe 30mph the temp got down to 180 again. Is the radiator causing this? Can it be that bad or maybe cracked heads? There is no oil in the water and no water in the oil. The water is not disappearing from the system, the radiator is allways full.