You don't need a fan that's larger than the original, but more importantly, how did you fit that in there? Is the shroud missing? If it is, that will let the hot air go back around repeatedly through the radiator and get hotter and hotter.
Most of these had electric fans, and since you found a related relay, I assume that's what you have. Obviously check that the fan is turning on. If the fan is dead, the engine will not run hot at highway speed.
The next thing is to look at the cooling fins on the radiator. If they're corroded and crumble easily when you rub them, that will reduce their effectiveness at giving up the heat to the surrounding air. The additional clue will be both radiator hoses are real hot.
If the cooling fins are in good shape and not blocked with debris, look for the rubber seal under the leading edge of the hood. That has to make a seal on the core support to prevent air from bypassing the radiator. There also can't be any holes in the core support, for the same reason.
Wednesday, August 12th, 2015 AT 7:31 PM