Cooling System

This section covers cooling system diagnosis and service, cooling system component removal, disassembly, assembly, installation, service procedures and specifications.

 WARNING: DO NOT STAND IN LINE WITH OR NEAR RADIATOR FAN BLADE (8600) WHEN ENGINE (6007) IS RUNNING.

 WARNING: NEVER REMOVE THE RADIATOR CAP (8100) UNDER ANY CONDITIONS WHILE THE ENGINE IS OPERATING OR WHEN THE COOLING SYSTEM IS HOT. FAILURE TO FOLLOW THESE INSTRUCTIONS COULD RESULT IN DAMAGE TO THE COOLING SYSTEM OR ENGINE OR PERSONAL INJURY. TO AVOID HAVING SCALDING HOT COOLANT OR STEAM BLOW OUT OF THE RADIATOR (8005), USE EXTREME CARE WHEN REMOVING THE RADIATOR CAP FROM A HOT RADIATOR. WAIT UNTIL THE ENGINE HAS COOLED, THEN WRAP A THICK CLOTH AROUND THE RADIATOR CAP AND TURN IT SLOWLY TO THE FIRST STOP. STEP BACK WHILE THE PRESSURE IS RELEASED FROM THE COOLING SYSTEM. WHEN YOU ARE SURE ALL THE PRESSURE HAS BEEN RELEASED, PRESS DOWN ON THE RADIATOR CAP (STILL WITH A CLOTH), TURN AND REMOVE IT.

The cooling system consists of the following components:

• Coolant, which consists of ethylene glycol antifreeze and water. It carries excess heat from engine to radiator where the excess heat is transferred to the surrounding air.
• Radiator, which allows excess engine heat to be transferred to the air.
• Radiator hoses, which attach radiator to engine.
• Water pump (8501), which circulates coolant through system.
• Passageways cast into the cylinder block (6010) and cylinder heads (6049), which allow coolant to circulate and absorb excess heat so that engine parts are not damaged by excess heat.
• Water thermostat (8575), which controls coolant temperature, allowing quicker engine warm-up improving fuel economy and reducing pollution.
• Bypass hose or passageway, which allows coolant to circulate within the engine when the water thermostat is closed preventing hot spots.
• Coolant recovery reservoir, which holds surplus coolant. When the system is hot and coolant expands, coolant goes into coolant recovery reservoir. When the vehicle cools, the system draws coolant back into the radiator, eliminating the need for frequent topping-off of the cooling system. The coolant recovery reservoir eliminates the loss of coolant through an overflow tube.
• Degas Bottle, which removes air and combustion gasses from the coolant. This maintains efficient heat transfer capability in the coolant.
• Pressure-vacuum radiator cap, which allows coolant to escape to coolant recovery reservoir when it expands so system pressure does not build, possibly bursting a hose or radiator tube. The radiator cap allows coolant to be drawn back in from coolant recovery reservoir when system cools, refilling system and preventing hoses from collapsing from a partial vacuum in system. The pressure-vacuum radiator cap also maintains 90kPa (13 psi) pressure in the cooling system. Pressurizing the cooling system raises the boiling temperature of the coolant allowing more efficient higher engine temperatures and reducing the risk of boiling over when driving at high altitudes.
• Engine cooling fan, which draws air through the radiator to help cooling at low speeds or when the vehicle is not moving. The system is designed so that air forced through the radiator by the forward motion of the vehicle is sufficient at driving speeds.
• Fan clutch (8A616), which decreases engine power needed to drive fan by allowing fan to free-wheel when engine is cold or when vehicle motion forces air through the radiator. The fan clutch has a thermostatic control so that it drives the fan when the engine is hot and air flow from the vehicle's motion is insufficient.
• Drive belt (8620), which drives the water pump, fan and other accessories off of engine crankshaft (6303). Refer to Section 03-05 for more information on drive belt.
• Engine transmission fluid cooler (7A095). On vehicles with automatic transmissions, a provision is made for cooling the transmission oil by circulating running it through a cooler in the radiator.