Why does your 87 reliant overheat after having changed the radiator heater valve and thermostat?

If your 1987 Reliant is overheating after changing the radiator heater valve and thermostat, it could be due to several factors. First, ensure that the thermostat is installed correctly and is functioning properly; if it's stuck closed, it will restrict coolant flow. Additionally, check for air pockets in the cooling system that may have formed during the repairs, as these can impede coolant circulation. Lastly, verify that the radiator and heater valve are not blocked and that the water pump is working effectively to maintain proper coolant flow.