Well, I gave the radiator a good soak with white vinegar. It seems to
have helped quite a bit. The only real test will be getting it out in
some serious traffic or on the interstate.
For those not following my previous overheating thread, the temp gauge
was exceeding 210° (12 o'clock, or directly in the center of the
gauge). When I'd slow down in the stop-and-go traffic of Atlanta, the
truck couldn't dissipate the heat, so when I'd take off again, it'd
continue heating up. It was compounding and just kept getting hotter.
The only way I could keep it out of the danger zone was to run with the
heat on--not exactly fun in 95° weather.
I first connected a garden hose to the side of the heater box that
returns to the radiator. Then I flushed the whole system till it ran
clean. Then I removed the radiator, and after flushing it with clean
water, I capped it off completely, and filled it with White Distilled
Vinegar. I let it sit for about 3 hours, then drained it, flushed it
with water again, re-capped, and refilled it with vinegar. I drained
and flushed again after 3 hours.
I then filled it with vinegar a 3rd time and let it sit overnight.
This morning after a good flushing I reinstalled it with new hoses, and
ran a hose straight from the intake manifold to the radiator,
eliminating the heater core. (hopefully to improve the performance of
I took it out for a spin a few minutes ago, and it was better. In
fact, after trying some Prestone radiator flushing product (waste of
time if you ask me) I took it out on a cool night, and it still ran
hot. Today, it's 93° outside, and it did NOT overheat after the
vinegar treatment. I even tried to make it overheat by running up
steeper grades while keeping the carb out of power mode (richer) and it
would not get up to 210°. I don't know what temperature "normal" is,
but it's around the 1/3 mark on the gauge, 1/2-way being 210°.
Thanks to SnoMan for the vinegar suggestion and all the others who've
helped. I'll be installing an auxillary electric fan, maybe one of
those neat dual-fan setups, as time and money permit.