What causes a car to over heat.

Short answer, yes. But there are also other things that need to be checked out first. Thermostat operation, cooling fan operation, coolant condition and level, air flow through radiator, and coolant flow through system including water pump operation. So while you may have a head gasket leak, a thorough inspection may reveal other problems or even what may have caused the head gasket to fail in the first place. Clint