Aluminum heads...

AJ/FormS said

The problem is not the 200 by itself. It the change over time and the ease with which the temp rises.
I would suspect the airflow through the rad has been compromised. Either the condenser fins are packed with dirt or mud, or the rad itself may also have blocked fins.
If that don't find it I would be checking the exhaust back-pressure

'Course the check-engine lite is off;right?

As to the heads eroding into the rad, I guess that must take more than 17 years cuz my rad is is still fine.

Click to expand...

You are correct, no CEL. Exhaust is free flowing. Intercooler is in front of the radiator, looked at it the best I could, don't see any obstructions. While back a piece of a tarp got sucked up in front of the Intercooler. Truck still ran at its normal temperature so I don't know if some bent fins would be enough to cause this. Few months ago I had 7500 pounds behind the truck. Was only 55*...climbed the grade just across the bridge. Gauge hit an time high of 225*. Grade is perhaps a mile. Truck didn't even unlock the converter or come out of OD...so the truck wasn't working hard. Have hauled 14k up the same grade, in 90* heat....and the temperature didn't climb over 190*...something definitely ain't right.
I need to check my maintenance book...I may be wrong about the frequency of coolant changes. Of course the radiator has plastic tanks...so a simple rodding ain't gonna happen..