If the diagnosis made is a coolant fan electrical malfunction, refer to Engine Controls.

The engine coolant temperature switch will close the circuit to the temperature indicator (Temp) light when the coolant reaches the temperature range indicated on the sending switch.

The engine coolant temperature switch is not serviceable. If it is faulty, it should be replaced.

If the pressure in the cooling system is too low, or if the coolant does not contain enough ethylene glycol antifreeze, the coolant will boil without an overheat condition. Pure water can boil at 119 ° C (247 ° F) and the Temp indicator will not show an overheat temperature, even with a 103 kPa (15 psi) cooling system. Pure water lacks the necessary rust inhibitors and water pump lubricant. The engine should never be run without the cap, or with the cap loose, as the coolant will boil before the temperature display shows a high temperature reading.

When adding coolant, use a 50/50 mixture of water and GM Goodwrench® DEX-COOL ® or Havoline ® DEX-COOL ®. For freeze protection at temperatures less than -37 ° C (-34 ° F), add pure ethylene glycol antifreeze until the desired freeze protection is reached.

Notice: Do not add cold water to the cooling system with the engine at or above operating temperature. Adding cold water causes rapid cooling, resulting in possible engine damage.

The coolant level should be checked at each engine oil change, and kept at the proper level. When coolant must be added, do so at the reservoir (not at the radiator), unless the reservoir has been emptied by a large coolant loss. When this happens, let the engine cool, then add coolant to both the radiator and the reservoir.

Before draining the cooling system, inspect the system. Perform any service needed to ensure that the system is clean, does not leak and is in proper working order.

Refer to the Symptom Diagnosis Chart for further diagnosis.