it got hot and cracked the head..Air in coolant system?
pressure check the system to find the leak, if your adding coolant then there IS a leak, replace part that is leaking.check thermostat housing, hoses, heater core, and radiator for leaks. after the leak is fixed make sure to (burp) the cooling system.Air in coolant system?
Any air will take care of it self when you run the car to operating temp. The air will be forced from the block in to the radiator. Sounds like you have a leak or a cracked block. Park the car and let it run for several minutes and watch for any leaks dripping to the ground. If not It's possible you have cracked the block and water is leaking internally. Check for water in the oil. Is the engine running any different due to water leaking into the cylinder and being burnt off with the gas. If so would will need to see auto shop. It can also leak from the heater core-- Check the passenger side front floor to see if it is wet-- if so you have a leaking heater core.Air in coolant system?
There may be a bleeder screw close to the thermostat housing. I like to warm the engine up with the radiator cap removed and parked facing up a hill. That way any trapped air bubbles will tend to rise to the top of the radiator. Keep the radiator topped off as the engine warms up. You can actually measure the temperature of the coolant by pointing a non-contact Infrared temperature meter at the thermostat bell housing. That way you can calibrate your dash temperature gauge and make sure it's reading right. If the car overheats while traveling at highway speeds, it would seen you either have a plugged radiator, or maybe a head gasket that lets hot exhaust gases into the coolant. A simple gas tester held near the mouth of the radiator (cap off) will register the presence of exhaust gases in the coolant. If you didn't change your coolant every 2 years, even your water pump impeller blades may be eaten up partially by corrosion. The water pump will leak from the weep hole under the pulley shaft and leave tell-tale white residue stains typically and eventually start leaking coolant under the engine. If you haven't changed your timing belt, change the water pump at the same time with a new tensioner pulley.