The Cooling System

What does it do? Maintains a constant engine operating temperature It removes excess combustion heat to prevent engine damage Also speeds engine warm-up Lubricates water pump

Cooling system types Liquid cooling Air cooling Surrounds the cylinder with coolant Is circulated through the water jackets by the water pump No hot spots/constant temperature Air cooling Circulates air over cooling fins on the cylinders Can be found on motorcycles, lawn mowers, and a few high-performance cars. Can not maintain as constant a temp as liquid cooled engines Lightweight/cheaper

Liquid cooling Advantages More precise control of engine operating temperature Less temperature variation inside engine Reduced exhaust emissions because of better temperature control. Improved heater operation to warm passengers

Basic Cooling system Water pump: Radiator hoses: Radiator: Forces coolant through the engine and other system parts Radiator hoses: Connect the engine to the radiator Radiator: Transfers engine coolant heat to outside air Radiator cap regulates pressure

Basic Cooling System Fan: Thermostat: Heater: Draws air through the radiator Thermostat: Controls coolant flow and engine operating temperature Heater: Provides warm air for passengers

Cooling System

4 Functions of Antifreeze Prevents winter freeze up Prevents rust and corrosion It provides a protective film on part surfaces. Lubricates the water pump Cools the engine Antifreeze conducts heat better than water and therefore cools the engine better Higher boiling point than water alone Boiling point rises 3 degrees for every PSI!

Coolant mixture 50/50 mix is best for most conditions Will provide protection from ice formation to about -34°C (-37°F) Very cold climates may need higher ratios of antifreeze

Reaching operating temperature quickly… or else! Poor combustion Part wear Oil contamination Reduced fuel economy Increased emissions

The Thermostat Senses engine temperature and controls coolant flow through the radiator. It reduces coolant flow when the engine is cold It increases coolant flow when the engine is hot

The Thermostat Can be located at either the coolant inlet or outlet on the engine. Normally fits under a thermostat housing

Thermostat rating Stamped on the thermostat to indicate the operating range Normal ratings are between 180°F and 195°F (82°C and 91°C) Higher thermostat heat ranges are used in modern autos because they reduce exhaust emissions and increase combustion efficiency

Thermostat Operation When the engine is cold, the thermostat is closed and the coolant cannot circulate through the radiator. Instead the coolant circulates around inside the engine until the engine is warm

Thermostat Operation The thermostat has a wax filled pellet contained in a cylinder and piston assembly When the thermostat is heated, the pellet expands and pushes the valve open. Coolant then flows past the thermostat

Wax pellet cut away

Thermostat Operation As the pellet and thermostat cool, spring tension overcomes the pellet expansion and the valve closes

The thermostat will open gradually as the heat melts the wax pellet This gives a the engine a very consistent operating temperature Usually between 180°F and 210°F

Testing Coolant Check water/antifreeze mix with hydrometer Check conductivity with multimeter Check Acidity with test strips

Testing with a hydrometer

Testing with a multimeter

Testing with PH strips

Pressure test cooling system and cap to rated PSI

Check water pump water pump leaks by weep hole? water pump creates flow? water pump makes noise? Check Thermostat is working!

Chapter 40 p.730 Review Questions #1-15 p.749

Cooling System Quiz Why are air cooled engines used? What is the typical radiator cap pressure? What is a thermostat and what is its job? Why is it important for an engine to warm up rapidly? What is one advantage of water cooled engines over air cooled?