Where is the thermostat on a 1999 Corvette?

The thermostat on a 1999 Corvette C5 is located on the engine, underneath the intake manifold. It's not easily accessible without removing parts of the intake system. You'll need to consult a repair manual specific to the 1999 Corvette C5 with your engine type (LS1 or LS6) for detailed instructions and diagrams.