Q: Truck is overheating and the heater is blowing cold air.

asked by on December 20, 2016

It started overheating and the heater blows cold air. Yesterday I replaced water pump and thermostat, same problem. The upper radiator hose is hot and the lower radiator hose is cold.

My car has 180000 miles.
My car has a manual transmission.

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Hi there. There is a blockage in the engine preventing the engine from cycling the coolant. If there is a new water pump and a new thermostat, then the coolant should be cycling. Check the radiator for any blockages. Drain out the coolant into a clean container and move aside. Then remove both the upper and lower radiator hoses on the radiator. Put a garden hose on the top of the radiator and fill up the radiator. If nothing comes out of the lower radiator port, then the radiator is plugged and needs replaced. If the water flows smoothly through the radiator and comes out, then remove the thermostat and put the hose where the thermostat was and see if water will come out of the lower radiator hose. If nothing comes out, then there is a blockage in the engine preventing the coolant from moving. If water comes out smoothly, then the thermostat was installed upside down. If you need further assistance with the engine coolant not cycling, then seek out a professional, such as one from Your Mechanic, to help you.

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