My carburated 1500 (D15A2) civic EW1 (115k mi) is pushing out coolant. The story goes like this, the impellar fell off the water pump shaft and then it came to me. I replaced the water pump hoping that there was no damage. Got it all back together with new belts, hoses, etc and took it for a ride. Idles rough and takes a long time to warm up. Last time out I replaced the radiator cap with a new one, filled the system with water and left the overflow empty. I went for a 10 mile drive and then checked the overflow. It was nearly at the top with water even thought the engine temp barely reached 1/8 of the normal range. Left it sit for an hour but the water stayed in the overflow. Drained the system and the water is milky white, maybe a stop leak had been added or is this consistent with combustion gases entering the cooling system? The only cooing system components I haven't replaced are the radiator and the thermostat, but they are both gonna be done next. I need some advice, I suspected the head gasket all along but sometimes I jump to conclusions and do stuff that doesn't need to be done.