Hi there -

My '91 has developed a nasty heating up problem.

When i accelerate, the temp guage goes from the "o" in normal way up
sometimes to the "l" or higher.  When you coast it drops back down again.
At a stop light to goes right back to the the "o".  Hit the gas and within a
minute - it shoots right back up again.  It also does this in park, if you
rev the engine up to 2800 and hold it there.

I changed the thermostat tonight and had no improvement.  Last summer I
replaced the radiator, fan clutch and water pump - mainly due the the age of
the items.  Two years ago, the temperature sender died and we replaced it.
We have not used the truck very much in the last year, if that makes a
difference.  We finally replaced the u-joints in the rear drive shaft to get
rid of the nasty 35 - 45 virbrations.  We now have 186,000 miles.

What kind of ideas are out there?

Thanks in advance,

Randy