Why does the Tekkit (New) Buildcraft Redstone Engine get overheated in the nether?
Solution 1:
In recent versions of Buildcraft, Redstone Engines can't overheat. Turning green and orange and speeding up is good, this means they're getting to operating temperature. Only if they turn red and stop, that means you've got a problem, but, as answered here, Redstone Engines don't do that.