My friends 94 Honda Civic is having an overheating problem. He had a leaking water pump which would drain the coolant, and it would than overheat. He overheated the car a few times. I replaced the water pump and timing belt, and it doesn't leak any more. Also replaced the thermostat. When he starts the car now, it still overheats. Blocked coolant passage maybe? Any ideas on what is wrong?