4AGE 16V engine overheat when at high speed

[Dave W]

I would first do a compression check, even if you do not have milky coolant. About the only thing left is the actual radiator. You could try a coolant flush to see if that might help. Clean the rad surface, straighten out bent fins, or find a rad shop that can rod the radiator. But you probably looking at a new rad. You can confirm insufficient Flow thru the rad, by seeing if running the heater reduces the temp. You do have an over flow tank connected in your system? I know my cooling system takes 2 or 3 short runs, then topping off the over flow tank, after cool down, to be able to get all the air out of the 4AGE cooling system.
Dave W