I have a new water pump and radiator. The thermostat was replaced, then removed. The oil is clean. My car is still overheating.
The cooling system would need to be tested to see if the combustion gasses are getting into the cooling system from a blown head gasket, or cracked head or block. This test involves a tester at the radiator to measure potential gas buildup in the cooling system. The thermostat should be installed again, since it is needed to manage the flow of coolant through the engine. I recommend that you hire a mechanic, such as one from YourMechanic, to run a diagnostic on your overheating issue, which would likely involve the test mentioned above.
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