I know the truck is running at the correct temp because the everything
Jonathan mentioned as in belt, water pump, thermostat and sending unit
have been replaced or checked. The radiator is not clogged either. Bleed
the air out of the radiator? That's a new on me. The temp. gauge needle
would bounce from cold to high, not a gradual move. The check engine
light only came on when the temp needle bounced into the hot range. The
needle is now in the hot range with or withot the key on now.
So I still think it is the gauge or can anyone tell me if there are 2 temp
sending units. I read in another persons question that his GMC engine had
2, one in the manifold by the therm. housing and one near the #2 and 4
cyl. I am not at the truck but will check it this weekend.