If your car is still overheating after changing the head gasket, there are several potential causes. First, make sure that the new head gasket is installed correctly and that all of the bolts are tightened to specifications. If the head gasket was not installed correctly or if the bolts are not tight enough, this can cause a leak in the cooling system which will lead to overheating.
Another potential cause for overheating could be a faulty water pump. The water pump circulates coolant through the engine to keep it at the proper temperature. If the water pump is not working properly, it can cause the engine to overheat.
Another possibility is a clogged radiator. The radiator needs to have good airflow so that it can effectively cool the engine coolant. If the radiator is clogged with debris or bugs, this can restrict airflow and cause overheating. Inspect the radiator and clean it out if necessary.
Finally, check thermostat for proper operation. The thermostat controls how much coolant flows through the engine. If it is stuck open, too much coolant will flow and this can cause overheating because it prevents proper heat transfer from occurring within the engine.