OK, overheating first.
I assume you have no leaks anywhere in the system. Just in case crawl under the front of the vehicle. Look up at the bottom of the water pump. You will see a small hole. Is it filled or dripping coolant, any amount, even a drop? Yes, replace your water pump it is finished. NO coolant visible, it will certainly be a tempurature sending unit, usually the defective one will be on the intake manifold near the thermostat housing.
Before you replace this part though, when was the last time your drive belt was replaced? Push down on it. Does it move more than 1/2 inch? If yes, replace it it should not move more than a 1/4 inch.
Overcooling: you said your thermostat is new, that cannot be one of the problems. You said the temp gage works fine. So that cannot be the other reason for overcooling.
Look at it logically. Check your drive belt condition first More than 2 to 3 years old replace it anyways. Then Check the water pump for defects. Start the engine with the rad cap off heater on high, and watch the flow of rad fluid. Really good flow as it warms up, put cap back on. Rev engine to about 2000 rpm for 1 min. Build up pressure in system. Is the top rad hose hot and really tight to squeeze. If yes, pump ok. No? Check under car while running check the weep hole for even a single drip. Clean/no drip, pressure in system, heat in truck runs well, at this point you will nedd to replace your temp sensor.
How old is your rad cap? If original replace it now. Clean out he coolant resovoir and refill to cold line with 50/50 mix.
For more help just ask.
Thursday, December 14th, 2006 AT 4:12 AM