I'm at a loss on this one and I need some new ideas. Been fighting this on my Ramcharger since the beginning. 1985 4wd with a 318/727.

Plain and simple, it won't control the water temp on the highway. It will idle at 160° until it runs out of gas, you could drive it from NY to LA as long as you never got on the interstate. But start pushing the speed to 65 and beyond and that temp needle will slowly climb and climb until you back it down to 55 again.

First of course you say this is classic symptom of a plugged up radiator. Second you think maybe there is an airflow problem. After that you start reaching for ideas. I'm well past all of that, well past the "replace everything" stage. I'll summarize with bullet points.

- new 3 core radiator (replaced twice)
- new hoses (lower has the spring in it to prevent collapse)
- thermostat (replaced twice)
- water pump
- all air baffles in place
- engine is clean, no dirt/grease blanket etc.
- coolant is perfect color, nice and clean, so no crud is circulating in it
- no water in oil, no oil in water, no exhaust gases in water, no leaks anywhere inside or out
- runs perfect


Basically I'm down to replacing the engine, but I refuse to believe there is anything wrong with this engine, I have to be missing a clue somewhere. I'm serious, you could idle forever in traffic on a 100° day and barely crack the thermostat open. You could drive around the world at 55 MPH. Oil pressure etc. is perfect. There is no way this engine needs to be replaced.

Any other ideas?