Engine Cooling Systems

The ILM states that the main purpose of an engine cooling system is to:

Keep the engine as cold as possible at all times Maintain engine temperature within an optimum range for performance, efficiency and durability Heat the passenger compartment directly Cool only the transmission and differential

The three basic methods of heat transfer described in the cooling systems ILM are:

Absorption, reflection and refraction Conduction, convection and radiation Compression, expansion and evaporation Boiling, condensing and sublimation

Conduction in an engine cooling system occurs primarily when:

Heat moves from hot engine metal into the coolant in contact with it Hot air leaves the radiator fins to the atmosphere Coolant circulates through the pump Air passes through the grille

Convection in the cooling system is best described as:

Heat transfer through solid metal only Heat transfer by movement of the coolant and air as fluids Heat transfer by electromagnetic waves only No heat transfer at all

Radiation in an automotive cooling system is mainly:

Heat transfer by direct contact between metal parts Heat radiated from hot engine and exhaust components to surrounding air and nearby parts Heat picked up by the air conditioning evaporator Heat moving only inside the combustion chamber

The ILM explains that the basic components of a liquid cooling system include:

Radiator only Radiator, water pump, thermostat, hoses, passages, fan and coolant Only water pump and thermostat Only overflow bottle and pressure cap

Modern coolants are typically mixtures of:

Straight water only Ethylene glycol or propylene glycol with water plus additive packages Engine oil and water Alcohol and gasoline

One major function of antifreeze, besides freeze protection, is to:

Increase exhaust emissions Raise the boiling point and provide corrosion and cavitation protection Reduce oil pressure Increase combustion temperature

The ILM distinguishes between conventional 'green' coolant and extended-life coolants mainly by their:

Colour only Corrosion inhibitor chemistry and service life intervals Density Freezing point

A water pump in a typical automotive cooling system is usually a:

Reciprocating piston pump driven by air pressure Centrifugal pump driven mechanically by the engine or belt Hand pump used only at start-up Gear pump located in the fuel tank

The thermostat in a cooling system is designed to:

Reduce oil pressure Restrict or allow coolant flow to the radiator to maintain engine operating temperature Pump coolant through the block Control radiator fan speed directly

The ILM notes that most thermostats begin to open at approximately:

40–50°C 80–90°C (typical modern engine range depending on application) 120–140°C 0°C

A radiator pressure cap raises the boiling point of the coolant by:

Adding more coolant to the system Allowing the system to operate under pressure above atmospheric Cooling the coolant chemically Reducing engine compression

If a cooling system is operated with no pressure cap or a failed cap, the likely result is:

Higher boiling point and less chance of overheating Lower boiling point and increased chance of boil-over Improved fuel economy Elimination of cavitation

The ILM describes that crossflow radiators differ from downflow radiators because they:

Use no fins Route coolant horizontally across the core instead of vertically Operate without coolant Eliminate the need for a fan

Electric cooling fans are controlled by:

The brake pedal position Thermal switches or the engine control module using temperature and A/C inputs Battery voltage alone Exhaust system backpressure

A thermostatic fan clutch on a belt-driven fan operates by:

Locking the fan solid all the time Using a temperature-sensitive fluid or bimetal control to engage more strongly when air leaving the radiator is hot Using coolant pressure to stop the fan Using fuel pressure to adjust fan speed

Air-cooled engines mentioned in the ILM rely primarily on:

Water jackets and radiators Cooling fins and forced air flow over the cylinders and heads Oil coolers only Exhaust manifolds as radiators

Shutters or grille covers on some heavy-duty equipment are used to:

Increase air flow at all times Control air flow through the radiator to help the engine warm up or maintain temperature Reduce cab noise only Increase exhaust restriction

A plugged or restricted radiator core will usually cause:

Low engine temperature Overheating under load or at highway speeds Faster warm-up and improved heater output Reduced fuel consumption

The ILM emphasizes that improper coolant disposal:

Has no environmental impact Is hazardous to the environment and animals and must follow approved procedures Improves soil quality Is recommended if coolant is old

Electrolysis corrosion in cooling systems is caused by:

High oil pressure Incorrect electrical grounds and stray voltage in coolant attacking metals Low tire pressure Brake fluid contamination

Cab heater cores are essentially:

Fuel coolers Small radiators that use engine coolant to supply heat to the passenger compartment Oil coolers in the trunk Exhaust gas recirculation devices

From a parts technician’s viewpoint, common cooling system replacement parts include:

Only exhaust manifolds Radiators, caps, hoses, thermostats, water pumps, heater cores, fans and fan clutches Only brake pads Only wiring harnesses

Cavitation erosion around cylinder liners is reduced by:

Using straight water only Using correct coolant mixture and additive packages specified for liner protection Eliminating all additives Overheating the engine regularly

A temperature gauge or warning light in the cooling system is used to:

Control power steering pressure Indicate engine operating temperature and warn of overheating Measure battery voltage Control transmission shifting

The ILM notes that coolant mixture is typically:

10% antifreeze, 90% water for all climates About 50/50 antifreeze and water in many automotive applications unless otherwise specified 100% water in all conditions 100% antifreeze in all climates

Cooling system bleed screws are provided to:

Add extra coolant to the system Release trapped air from high points in the system to prevent hot spots Increase system pressure Measure oil level

Low coolant level can result in:

Improved temperature stability Overheating and possible engine damage due to lack of heat transfer Higher fuel economy Reduced emissions only

The module stresses that mixing incompatible coolant types can:

Always improve corrosion protection Cause sludge, reduced inhibitor performance and possible cooling problems Have no effect on system performance Increase heater output

A coolant recovery or expansion bottle is used to:

Store fuel Capture expanding coolant when hot and return it to the radiator as the engine cools Measure oil pressure Raise engine compression

When selecting replacement radiators, the ILM indicates that important details include:

Vehicle colour and trim package only Core size, thickness, row count, inlet/outlet locations and transmission/oil cooler provisions Only approximate physical size Type of floor mats installed

On heavy-duty trucks, additional coolers may be provided for:

Window glass Engine oil, transmission fluid and charge air (intercooler) Seat fabric Washer fluid

Air flow across the radiator at low speed is primarily provided by:

Vehicle motion alone Engine-driven or electric cooling fans Alternator output Intake manifold vacuum

The ILM stresses that cooling system service opportunities for parts technicians include:

Only coolant sales Coolant, flush chemicals, caps, hoses, clamps, thermostats, pumps and heater parts Only engine blocks Only transmissions

On some equipment, shutters or winter fronts must be used carefully because:

They cannot affect engine temperature Excessive restriction can cause overheating under load if left closed They always improve cooling They only affect cab comfort

Coolant hoses are typically reinforced because they:

Carry only low-pressure vapour Must withstand system pressure, temperature and pulsation without collapsing or bursting Are not exposed to heat Only guide wiring

A slipping drive belt for a water pump and mechanical fan can cause:

Improved cooling and charging Reduced coolant circulation, reduced fan speed and overheating Lower engine temperature at all times No change in system operation