I had a hairline crack in coolant reservoir causing engine to overheat. I replaced the reservoir and still having overheating problems. What can be causing this?

If you replaced the coolant reservoir and are still experiencing overheating, there could be several other issues at play. Potential causes include a malfunctioning thermostat that isn't opening properly, a failing water pump that isn't circulating coolant effectively, or a blockage in the cooling system. Additionally, check for air pockets in the cooling system or possible leaks elsewhere that could be leading to insufficient coolant levels.