Honda Repair: Prelude Over Heating, thermo fans, coolant level

Question
I have a 96 prelude and since I bought it about 12 months ago it has over heated on me twice. I have changed the coolant, changed the radiator cap, changed the thermostat. And the thermo fans work fine. I watch the water level like a hawk for weeks and it doesnt change. It pushes out a small amount of coolant into the overflow when the car is driven then pulls it back when sits over night. And maintains the same coolant level. It just every so often pushes a heap of water out of the radiator and over heats. I fill it back up and its fine for another month or two. Its not when the car is working hard. I drove it for a whole month with ac on in heavy traffic in 40 degree temps and it was fine. And yet it just got hot on me driving on a cold day on the freeway. Could it be a head gasket? Or blocked radiator? Or water pump. How can I check these things?
Thanks for any help
Kelvin

Answer
most likely its your water pump, if you change it and it continues then it could also be the head gasket. You may want o have the radiator flushed also. If you flush it and replace the water pump and everything is fine....You have saved yourself a lot of money.Please send me a follow up