Hi, I bought a used Civic recently and had an issue where the temperature gauge was reading really cold, just above the lowest reading (1/4) most of the time but occasionally after long drives and particularly in traffic would read really hot (3/4) and would only cool off at high speeds. I replaced the temp sensor and thermostat (it turned out the previous owner had removed the thermostat, and even with the new thermostat it’s still running cold. I also hear the sound of sloshing water which I understand could be either low coolant or an air bubble but shouldn’t it run hot in that case?