Before dumping any more money into it, I would measure the temperature going
into and coming out of the radiator. This will tell you if it is doing its
job or if it might be a sensor problem. Some engines will get hotter when
shut off because of residual heat that is not taken away by circulating
water.

How stock is the engine, fan, and radiator? Is it missing a fan shroud? Are
the pulleys the correct diameter? Could be timing or carburetor adjustment.
The obvious is the thermostat. Has it always done this or is it a new
problem? Was coolant used when parts were new? water only would cause
corrosion.



> wrote in message
ups.com...
> Have a 68 Buick with a 430 V-8. The "Hot" light comes on when the car
> has been driven and then sits with then engine off for approximately 20
> min. If the car is started and the light comes on, I can rev the
> engine up a bit and the light will go out. If I drive it below 75mph
> the temp light stays out...if I drive it fast...then slow down and
> drive 65mph...the light eventually comes on.
> The engine was rebuilt about 2 yrs ago, the engine has a new radiator,
> water pump, themostat and temp sensor. I took a chance and replaced
> the water pump....no such luck. The sensor was checked to make sure it
> works...works fine. I am thinking about replacing the radiator and
> finding a differant fan. Any thoughts? Please contact me at
> .
>
> Thanks!
>