Cooling System Function

The air and fuel mixture exploding inside the engine produces the power needed to move the vehicle. This combustion process also produces great heat that, if left uncontrolled, can damage the engine and reduce its operating efficiency. The cooling system removes enough heat to keep the engine at a safe temperature for best performance. A secondary function of the cooling system is to provide interior cabin heat during cold winter.

Components of the Cooling System

Coolant: Commonly called antifreeze, this specially formulated liquid flows around the cylinders through hollow passages in the metal engine block called the water jacket. The coolant absorbs the heat from combustion, then continues through the cylinder head out to the other cooling system components where it transfers heat to the atmosphere.

There are two coolant varieties widely in use today. Green-colored ethylene glycol is the type commonly used for more than 35 years. The newest type is an orange-colored, extended-life coolant first introduced on General Motors vehicles in 1995 to reduce maintenance requirements. This coolant is ethylene glycol with special additives to reduce chemical reactions between the coolant and engine metals. Extended-life coolant cannot be mixed with tap or well water at any time. It must be mixed with distilled water only. For the extended-life coolant to truly be “extended life", an additive package must be added at about 2.5 to 3 years of use, or it must be serviced as if it were conventional coolant. These two types of coolant should not be mixed in the cooling system since the individual additive packages are incompatible with one another.

Water Pump

This component is belt, gear, or electrically driven to pump coolant through the engine block and cylinder head, then it forces fluid out to the other parts of the cooling system.

Radiator

This component transfers engine heat to the atmosphere. Hot coolant flows through radiator passages called coils, which are surrounded by numerous metal surfaces, called fins. Air flows through the radiator, and across these fins to remove engine heat from the coolant. Radiators are made from special metals such as aluminum and brass that help transfer heat quickly to the surrounding air.

Hoses

These components allow coolant to flow freely from the engine to the radiator and heater core.

Thermostat

This component is a spring-loaded valve that reacts to heat by opening to allow hot coolant to flow from the engine to the radiator at a predetermined temperature.

Radiator Cap

This component maintains a constant pressure on the cooling system to raise the boiling point of the coolant, and ensure a consistent supply of fluid to the water pump.

Drive Belts

These components are V-shaped or flat, ribbed rubber belts that use engine power to turn various engine accessories such as the water pump, and cooling fan.

Heater Core

This component is really a small radiator that is used to heat the passenger compartment during cold weather. When the heater control valve is open, hot coolant flows through the heater core as the ventilation fan forces air across the fins to provide warmth.

Fan Clutch

This component reduces drag on the engine by slowing cooling fan speed. Non-thermal clutches depend upon engine speed and resistance within the clutch to vary cooling fan speeds. Thermal clutch mechanisms react to engine temperatures by varying the clutch resistance to alter fan speed.

Hose Clamps

These components secure pieces of the cooling system together to create leak-proof seals. Replacement clamps use a worm-gear drive that makes them easier to remove and replace than many factory-style clamps. Replacement clamps also often have a greater clamping surface than original equipment fasteners.

Causes of Component Failure

The number of miles a vehicle has traveled causes less worry than the age of the vehicle when dealing with cooling system maintenance. As vehicles age, they encounter extreme temperature changes, and prolonged exposure to harsh chemicals. Operating under these conditions has a negative effect on the cooling system, causing such problems as corrosion, heat cracking, dry rot, and chemical deterioration. Here are some common problems facing individual cooling system components.

Coolant

Quantity – Low coolant levels can create air pockets in the system, which may cause damage to the aluminum water pump impeller as well as other aluminum engine components. Low coolant levels also do not allow the system to build up the required pressure for effective heat transfer. Quality – Coolant loses its lubricating and corrosion-inhibiting properties over time. Chemicals in the coolant break down from exposure to too many heat cycles, so replacing it periodically maintains its protective value. Having only water in the system combined with excess engine heat will cause rapid corrosion in many metals. Adding coolant to water in the recommended ratios raises the boiling point of the mixture, and lowers its freezing point.

Water Pump

Over-tensioning of the drive belt can cause premature shaft bearing wear on the water pump. Improper lubrications can also cause bearing failure and coolant leakage from seal deterioration. Corrosion can also destroy the impeller and pump cover.

Thermostat

Corrosion can cause the thermostat to either stick open or hold shut. Thermostats with an improper temperature rating can adversely affect engine operation. A colder-rated thermostat will not allow the engine to warm up to proper operating temperature during colder weather, which can adversely affect drivability, increase emissions, and decrease gas mileage. Using a hotter-rated thermostat will not warm up the engine any faster. Instead it can make the engine run too hot, possibly causing pre-ignition and detonation.

Radiator

Corrosion ruins radiators by causing leaks wherever the thin metal is eaten through. Scale can break loose from the walls of the radiator and cause damage to other components as it migrates through the cooling system. Mineral deposits can plug the radiator, hoses, and heater core as well as coolant passages in the block and head.

Hoses

Exposures to harsh chemicals and high heat can deteriorate hoses from the inside out, causing them to collapse and restrict coolant flow through the engine. Such internal damage may not readily be noticeable to the eye or touch. Hoses can also split and crack, as well as develop soft spots that may eventually cause them to burst.

Preventative Maintenance

The best time to perform maintenance on the cooling system is before it fails, stranding you or your customer alongside the road. Here are some tips and general guidelines to help prevent a cooling system-related breakdown.

Coolant:

• Loses protection and lubrication abilities over time
• Should be changed every 2 years on older vehicles or vehicles with known corrosion problems
• System needs to be kept at full level for maximum protection
• Follow manufacturer’s recommended coolant change intervals and mix ratios
• Use phosphate-free coolant with aluminum radiator and engine constructions
• Use approved coolant in late model vehicles to satisfy warranty requirements
• Extended-life coolants lengthen change intervals, provide superior protection for system components, and satisfy most manufacture’s warranties
• Dispose of used coolant in an environmentally responsible manner

Chemicals

• Additives inhibit corrosion and lubricate moving parts for quiet operations and long service life
• Chemical flushes help loosen scale and deposits to improve cooling system efficiency
• Flushing the system removed contaminants and scale that can damage new parts or interfere with proper operation
• Cooling system should be flushed prior to the installation of new parts or the addition of fresh coolant
• Available flush kits and adapters ease procedure

Hoses

• Deteriorate from exposure to high heat, and harsh chemicals
• Need regular inspection and periodical replacement to prevent the inconvenience of unexpected failure
• Should be replaced to contain higher system flow volumes generated by new parts

Radiator cap and thermostat

• Are mechanical devices with moving parts that wear out
• Corrode and deteriorate from exposure to high heat, and immersion in liquid
• Should be replaced to ensure proper system operating temperatures and pressure

Belts

• Deteriorate and crack from exposure to high heat, and the physical stresses of operation
• Should be replaced to prevent the inconvenience of unexpected failure, and to ensure proper operation of new parts
• A good time to change belts is when components are made accessible by related repairs

Hose clamps

• OEM-style clamps typically are a single-use design that loses spring tension over time
• Should be replaced with hoses to ensure proper sealing and system operation
• New worm drive clamps typically speed installation time and allow future ease of service

Fan clutch

• Should be inspected for wear and correct operations
• May cause overheating condition symptomatic of other component failure if defective
• May cause premature pump shaft bearing wear or water pump failure if worn or defective

Gaskets and sealant

• Fills surface imperfections on mounting surfaces to ensure leak-proof installation
• Should be applied sparingly to both mounting surfaces to be mated together
• Should be applied sparingly to both sides of mounting gasket