If you diagnose a cooling fan electrical malfunction, refer to Engine Electrical.

The engine coolant temperature switch closes the circuit to the temperature indicator lamp (TEMP) when the coolant reaches the temperature range on the sending switch. The engine coolant temperature switch is not serviceable. If the switch is faulty, replace the switch.

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 lubrication.

Do not run the engine without the pressure cap, or with the cap loose, because the coolant will boil before the temperature display shows a high temperature reading.

When you add coolant, use a 50/50 mixture of water and DEX-COOL™ antifreeze. For freeze protection at temperatures less than -37°C (-34°F), add pure ethylene glycol antifreeze until you reach the desired freeze protection.

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.

Check the coolant level at each engine oil change. Maintain the coolant to the proper level. When you need to add coolant, add coolant to the recovery reservoir (L36 & L67) or the surge tank (L47), unless the cooling system has been emptied by a large coolant loss. When this happens, let the engine cool, then add coolant to the radiator and the reservoir/surge tank.

Before draining the cooling system, do the following inspection on the system:

Do any service needed to keep the system working properly.