Overheating, tried (almost) everything.

[dagnabbitt]

This is a barn find I picked up a couple years ago, I have done the usual stuff that you do to a truck that sat for 15 years. New brakes all round, axle seals, new carb, plugs, wires, etc.

The truck is a hodge podge of what I imagine were spare parts. Its a 1981 with a pre-1976 stepside box, and a 1983-1984 front end. It seems like the interior is built the same way. When I got it it had a 1975 gauge package (or so), and nothing worked. I bought some NVU gauges, and thats when I found out I definitely had a cooling problem. The truck idles nice, and I can drive 40 mph all day long and itll stay at 180. When I take it on the highway though it climbs and climbs, it hit 250 today and I had to pull over.

So far I have:

- flushed the cooling system 3 times
- replaced the thermostat with a 165F
- replaced the rad cap
- moved the temp sensor from the head to the intake and back again.
- changed the oil, set the timing, and all the other stuff that can make a 5 degree difference.
- Although a new rad cap should eliminate the problem I still checked the hoses and none of them are collapsing under revs.


Am I avoiding the obvious... that I just need a new rad, or is there something I am missing?

Thanks all.