You intstalled a new thermostat and now radiator coolant is leaking?

If radiator coolant is leaking after installing a new thermostat, it could be due to a few reasons, such as improper sealing during installation or a damaged gasket. Check to ensure that the thermostat is correctly seated and that all connections are tight. Additionally, inspect the radiator and hoses for any signs of damage or wear. If the issue persists, it may be wise to consult a professional mechanic for a thorough diagnosis.