1993 blazer with a 4.3L vortec engine is showing overheating on guage. My brother replaced the thermostat, heater core, and waterpump. I noticed the gauge did not seem to work correctly, so I replaced the temp sensor and temp switch. Gauge works ok now, but vehicle heats up to 234-240+ on gauge. Top of radiator feels hot, but bottom feels cold. Do you think the radiator is plugged or could my brother have possibly put the wrong water pump on as I don't think it is circulating well? Any way to test to see if it is the water pump? Thanks! John (wolf654u@yahoo.com)

 

did he put the thermostat in correctly? as in not upside down?

 

Hi, The thermostat was in correctly and we tested it before we installed it to ensure it opens ok. We think that the temperature gauge may have a problem. With the engine idleing, the temp gauge is showing 240 degrees, but the motor has not even warmed up completely. You can still put your hands on the valve covers at this point and nothing is boiling out of the radiator with the cap off. We placed a themometer in the radiator and temp shows 165 degrees. Is it common to have temperature gauges go bad?

 

Sticking a thermometer in the radiator at the cap location is not a good indication of what the engine temperature is. #1, that is the cold side of the radiator.

Temp sending unit can go bad. It is not unheard of, but I would really suspect an air locked cooling system or something similar.