I experienced an overheat while hauling a heavy load (13K) up a 6-7% grade. I wasn't sure whether it was the water pump or cooling fan. During this time, the heat stopped working on the truck. I replaced the tstat, water pump, fan, and temp sensor. Now I am not getting a reading on my dash temp sensor gauge. I check the sensor with multimeter and all is well. What am I missing here?
My car has 260000 miles.
My car has an automatic transmission.
You may have a clogged heater core that may be prohibiting the outer linings of the heater core to get hot. As you know, the heater core is a series of tubes that the coolant runs through that generates the heat from the warm coolant after circulating through the motor. These tubes can occasionally develop a buildup on the inner walls such that when the heater core is "flushed" this buildup on the inner walls of the lines remains and still allows the coolant to flow through the heater core. It is important to note that when the heater core is "flushed" it is possible to get good flow through the heater core while the inside walls of the heater core remain caked with buildup. As a result, the buildup on the inner walls prevents the temperature from rising to its capability due to the insulating effect of this buildup on the inner walls which will prevent the necessary heat transfer to properly heat the inside of the car. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your heater core.