Honda Civic 2003. Expansion tank fills and radiator is empty on 3 occasions now. No white smoke or mixing of oil and coolant. Want to know how to see if radiator cap is broken but don't know how to check this. Also, just thought about buying a new radiator cap but the car parts place has 2 types?

If your engine is overheating, Try this procedure:

• Dirt and debris can get lodged in the radiator air flow paths. This can block the radiator and cause your engine to overheat and damage the engine.

• The thermostat can be stuck close. If you feel the upper hose very hot and the lower hose cooler than normal, it may be a stuck thermostat.

• Make sure the radiator and the overflow bottle are filled to the proper levels.

• Bleed air from the coolant system:This is best done by running the engine with the radiator cap off until you see when the air bubbles stop coming up.

• Check the radiator fans: The easiest way is to turn on the cars air conditioner and turn up the A/C fans. Both radiator fans should come on when the A/C starts

• Make a pressure test by using a pressure testing tool (available at most auto parts stores). Use the pressure shown on your radiator cap. Most cars are 16 PSI or less, so don't exceed that pressure. Replace the radiator cap if it doesn't hold the pressure.

1.take in a sample is the best method,2.to test a cap you need to put it under working presure