96 Chevy Lumina and Ive replaced the thermostat water pump and flushed the radiator on your 96 Chevy lumina and now it jumps from 125 to 260 while im driving?

Answer 1

You did not state whether you had this problem already before you did the work or if it suddenly started happening after. If it just started overheating after you did this, but was running fine before, the first place I would start is with the thermostat. I have bought a few over the years, that were defective right out of the box... that's why I test them all before I install them now. First, take the water neck off and make sure that you installed the thermostat correctly the first time and have the flow going through the thermostat in the right direction. If it was installed correctly, the next thing to do is take the thermostat out and test to see if it is opening as it should. Rinse it off thoroughly to get all of the antifreeze off it, put it in an old kitchen pan and fill it with enough water to cover it. Next put it on the stove and turn it on. Watch the thermostat to see when it opens... you can check the temperature of the water with a meat thermometer when you see the thermostat begin to open. I believe most thermostats open at around 190 degrees Fahrenheit now for most modern cars. Most should have it stamped somewhere on the thermostat. If the thermostat was installed properly and is opening at the correct temperature, then the next thing I would suspect would be a bad head gasket or a cracked cylinder head... which you would notice by a loss of antifreeze either around the outside of the head or internally either mixing with the oil and turning it a milky color or being burned with the fuel in the combustion chamber and producing a distinctive sweet smell at your exhaust.