The coolant temperature indicator system consists of a temperature gauge mounted in the instrument panel and a coolant temperature sending unit mounted on the engine directly below the distributor. If an overheating indication occurs even when the engine is cold, check the wiring between the dash and the sending unit for a short circuit to ground. If the gauge is inoperative, test the circuit by briefly grounding the wire to the sending unit while the ignition is on (engine not running for safety). If the gauge deflects full scale, replace the sending unit. If the gauge doesn't respond in the test, check for an open circuit in the gauge wiring. If the sending unit must be replaced, simply unscrew it from the engine and quickly install the replacement. Use sealant on the threads. Make sure the engine is cool before removing the defective sending unit. There will be some coolant loss as the unit is removed, so be prepared to catch it. Check the level after the replacement part has been installed.