96 honda civic running hot after a long drive at stop lightd?

I have a 96 honda civic just changed water pump, thermostat and all belts. Having to check oil every day, losing coolant out if radiator cap which is also fairly new. My husband drives about 200 miles a day, at a constant speed car runs great at normal temps but in the afternoon on his way home as soon as he gets into stop and go traffic temp goes up. What should we fix next?

Replace the radiator cap first - it is defective. I strongly recommend only an OEM cap, and the dealer is not a bad source. Then bleed the cooling system. On top of one of the housings where the radiator hoses connect to the engine there's a nipple, like an oversized brake bleed nipple. With the engine cool, open it 1/2 turn (12 mm socket) and close it when a steady stream of coolant comes out. This step needs to be done every time the coolant is refilled or after it gets very low.

The two of those have a decent chance of clearing up the problem. If not, the next step is to determine whether the overheating is due to lack of coolant flow or lack of air flow. If it is more convenient to check it at home, just let it idle until the temerature gets too high and then turn it off and feel the lower radiator hose. If it is cool the coolant is not flowing; if it is hot the coolant is flowing but the fan is not working. If it is more convenient to check it when he is on the road and the temperature is rising, he can rev the engine to about 2000 rpm for half a minute or so while watching the temperature gauge. Trouble with the coolant flow will show up as the temperature dropping now that he has the water pump turning at cruise speeds, but if the fan is not working the temperature will not drop. The fan also won't be on if the hot coolant is not flowing so that is not a reliable indicator of the fan itself being the problem so this test has to be done.