Fan clutch faulty.
Fan shroud missing or broken.
Radiator air flow may be blocked from outside with debris (leaves and stuff).
Assuming it did not overheat before you replaced thermostat and water pump you may have installed the thermostat backwards. It is also possible the cooling system wasn't refilled properly and was air bound.
We don't know what relay you are referring to. Check your thermostat and radiator fan. Fluch out your cooling system.
thermostat is more than likely stuck shut from the overheat. Have to be changed.
Possibilities: Cooling fan not working. Low on coolant. Clogged radiator, radiator hose or block.
You may have to replace the cooling fan relay or the cooling fan itself, I had the same problem and I first replaced the relay and it helped but then the cooling fan went out and I repalced it and now everything is fine.
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The sensor on the thermostat housing is a cooling fan switch. Cooling fan switch closes the circuit to engage the cooling fan(s) when the optimum temperature is reached. When not replaced, cooling system fans will either remain continually "on" or not function causing the engine to overheat, internal engine damage and/or temperature light illumination.
water pump or cooling fans or thermostat low coolant
A 1991 Subaru Impreza might overheat because of a leaking cooling system or because of a damaged thermostat. You might also have a damaged or leaking radiator or a cooling fan that is not working.
If your 2001 Chevy Silverado is still overheating after replacing the thermostat and water pump, check for other potential issues such as a clogged radiator, low coolant levels, or a malfunctioning radiator fan. Inspect the coolant for contamination, which could indicate a blown head gasket. Additionally, ensure that there are no leaks in the cooling system and that the radiator is functioning properly. If these checks do not resolve the issue, consider consulting a professional mechanic for further diagnosis.
Type your answer here... IF WE CHANGED ONLY COOLING FAN THEN IT WILL BE OVERHEAT BECAUSE WE DON'T CHANGE OR FLUSHING OF RADIATOR. WE CAN REMOVE THERMOSTAT VALVE ALSO MAY BE HOSE PIPE WILL BE BEND
If the electric cooling fan(s) are not coming on that may be the problem.