Cooling System: Description and Operation

GENERAL INFORMATION
The cooling system is designed around the coolant. Coolant flows through the engine water jackets absorbing heat produced during engine operation. The coolant carries heat to the radiator and heater core. Here it is transferred to the ambient air passing through the radiator and heater core fins. The coolant also removes heat from the automatic transmission fluid in vehicles equipped with an automatic transmission.

COOLANT PERFORMANCE
The required ethylene-glycol (antifreeze) and water mixture depends upon climate and vehicle operating conditions. The coolant performance of various mixtures follows:
^ Pure Water. Water can absorb more heat than a mixture of water and ethylene - glycol. This is for purpose of heat transfer only. Water also freezes at a higher temperature and allows corrosion.
^ 100 percent Ethylene - Glycol. The corrosion inhibiting additives in ethylene - glycol need the presence of water to dissolve. Without water, additives form deposits in system. These act as insulation causing temperature to rise to as high as 149°C (300°F). This temperature is hot enough to melt plastic and soften solder. The increased temperature can result in engine detonation. In addition, 100 percent ethylene - glycol freezes at -22°C (-8°F).
^ 50/50 Ethylene - Glycol and Water. Is the recommended mixture, it provides protection against freezing to -37°C (-35°F). The antifreeze concentration must always be a minimum of 44 percent, year - round in all climates. If percentage is lower, engine parts may be eroded by cavitation. Maximum protection against freezing is provided with a 68 percent antifreeze concentration, which prevents freezing down to -67.7°C (-90°F). A higher percentage will freeze at a warmer temperature. Also, a higher percentage of antifreeze can cause the engine to overheat because specific heat of antifreeze is lower than that of water.

CAUTION: Richer antifreeze mixtures cannot be measured with normal field equipment and can cause problems associated with 100 percent ethylene - glycol.

COOLANT SELECTION - ADDITIVES
Coolant should be maintained at the specified level with a mixture of ethylene - glycol based antifreeze and low mineral content water. Only use an antifreeze containing ALUGARD (TM) 340-2.

CAUTION: DO NOT use coolant additives that are claimed to improve engine cooling.

COOLANT SERVICE
It is recommended that the cooling system be drained and flushed at 84,000 kilometers (52,500 miles), or 3 years, whichever occurs first. Then every two years, or 48,000 kilometers (30,000 miles), whichever occurs first.

COOLANT LEVEL CHECK - ROUTINE
Do not remove radiator cap for routine coolant level inspections. The coolant level can be checked at coolant reserve / overflow tank.
The coolant reserve / overflow system provides a quick visual method for determining coolant level without removing radiator pressure cap. With engine idling and at normal operating temperature, observe coolant level in reserve / overflow tank. The coolant level should be between ADD and FULL marks.

ADDING ADDITIONAL COOLANT - ROUTINE
Do not remove radiator cap to add coolant to system. When adding coolant to maintain correct level, do so at coolant reserve / overflow tank. Use a 50/50 mixture of ethylene - glycol antifreeze containing Alugard (TM) 340-2 and low mineral content water. Remove radiator cap only for testing or when refilling system after service. Removing cap unnecessarily can cause loss of coolant and allow air to enter system, which produces corrosion.

COOLANT LEVEL CHECK - SERVICE
The cooling system is closed and designed to maintain coolant level to top of radiator.

WARNING: DO NOT open radiator draincock with engine running or while engine is hot and cooling system is under pressure. Serious burns from the coolant can occur.

When vehicle servicing requires a coolant level check in radiator, drain several ounces of coolant from radiator drain cock. Do this while observing coolant reserve / overflow system tank. The coolant level in reserve / overflow tank should drop slightly. If not, inspect for a leak between radiator and coolant reserve / overflow system connection. Remove radiator cap. The coolant level should be to top of radiator. If not and if coolant level in reserve / overflow tank is at ADD mark, check for:
^ An air leak in coolant reserve / overflow tank or its hose.
^ An air leak in radiator filler neck.
^ Leak in pressure cap seal to radiator filler neck.

LOW COOLANT LEVEL - AERATION
If the coolant level in radiator drops below top of radiator core tubes, air will enter cooling system.
Low coolant level can cause thermostat pellet to be suspended in air instead of coolant. This will cause thermostat to open later, which in turn causes higher coolant temperature. Air trapped in cooling system also reduces amount of coolant circulating in heater core resulting in low heat output.

DEAERATION
As the engine operates, any air trapped in cooling system gathers under the radiator cap. The next time the engine is operated, thermal expansion of coolant will push any trapped air past radiator cap into the coolant reserve/overflow tank. Here it escapes to the atmosphere into the tank. When the engine cools down the coolant, it will be drawn from the reserve / overflow tank into the radiator to replace any removed air.