Hi I have a 1985toyota corolla 1.3 GL 2A engine I didn't have coolant in the car so with it being summer now I noticed the heat gauge going up faster then normal but not too much to over heat. So I bought coolant and filled it in the radiator with just a liter if water now I'm noticing that on longer trips the car is cool and when parked off it's just below the hallway mark what can I do?

water expands and contracts with heat, if you don't have to keep adding water, that's normal. If you do have to add, try this video https://www.youtube.com/watch?v=evpaTW2WJ5Y