I have changed the thermostat, the water pump, the fan clutch and flushed the radiator but it's still overheating. What could be the issue?
My car has 150000 miles.
My car has an automatic transmission.
It sounds like you may have a restriction in your cooling system that is preventing the proper flow of coolant through the engine.
I would recommend having the system power flushed to remove any restrictions that may exist. The restriction is likely in the coolant passages inside the engine if the radiator and water pump have already been replaced.
If the power flush does not resolve the issue, it is possible that the engine may require an overhaul from a qualified professional in order to resolve this issue.
I would suggest having this overheating issued diagnosed by a certified technician, such as one from YourMechanic, for an accurate repair.