Chapter 14 Cooling System

Objectives Analyze wear and damage to cooling system parts Explain cooling system theory Select and perform most appropriate repairs to cooling system

Types of Cooling Systems Smaller engines are cooled by air only Most automotive cooling systems use liquid coolant Engine block and cylinder head have cast-in water jackets

Cooling System Parts Water pump or coolant pump Radiator Radiator hose The fan Thermostat Coolant

Coolant Pump Typically called a water pump Impeller type pump Mounted on front of engine and belt-driven Aluminum or cast iron Shaft supported by a bearing and uses a spring loaded front seal

Coolant Pump

Coolant Pump Failure Static Seal Bearing Impeller Pump plate leakage Coolant leaks from coolant vent hole Bearing Will also damage static seal Impeller Broken pieces of impeller can enter the block, and possibly the radiator Pump plate leakage

Possible Reasons for Pump Failure High engine miles Engine ran low on coolant Out of balance fan assembly Faulty fan spacer

Belt Materials Tensile chords provide strength V-ribbed belts ribbed on one side and flat on the other Thickness of v-ribbed belt allows it to wrap around smaller pulleys as well as bend backwards This allow both sides to transmit power

Accessory Drive Belt Service Check all belts for wear, cracks, or damage Replace glazed belt Check for proper belt alignment

Drive Belt Service

Thermostats Allows engine to warm up and maintain a constant temperature Made of brass or stainless steel Expansive wax compound expands at predictable rate to open valve Rated according to engine temperature

Radiators Cross flow or down flow style Coolant flows through radiator cores Cores are constructed from copper or aluminum Aluminum radiator cores conduct heat better than copper Plugged radiator will cause overheating

Heater Core Heat exchanger located inside passenger compartment Heat is transferred form engine into heater core then into vehicle Core can leak or become plugged Constructed of aluminum, copper, or brass

Hoses Consist of inner rubber tube, reinforcement, and outer rubber cover Have a burst strength five to six times the normal operating pressure

Hoses 3 types Straight Molded Universal

Cooling System Pressure Cap Putting system under pressure raises boiling point of coolant Each pound of pressure raises boiling point three degrees Cap includes a valve that allows coolant back into radiator as temperature drops

Radiator Pressure Cap

Radiator Fan Draws air through radiator at idle and low speeds Aluminum, plastic, or steel blades Most late model vehicles use a fan driven by an electric motor Some rear wheel drive vehicles still use belt driven fans

Coolant Additives Borax Phosphate Sodium molybdate Sodium silicate Sodium nitrate Triazoles

Coolant Additives Sodium hydroxide Phosphorescent Benzoate Water

Electrolysis Destructive to engine cooling system Three types Chemical electrolysis Coolant has become too acidic Caused from dissimilar metals in cooling system Faulty electrical ground Static electricity

Checking Coolant Conductivity Ground positive probe by grounding it to radiator Insert negative lead into coolant Reading should be .2 volts or less If reading is .5 volts or more System should be flushed and refilled with new coolant

Checking Coolant Conductivity

Testing Coolant Condition and Strength Test strips can check pH, cavitation additive protection, and coolant concentration Conventional coolant has a higher pH than extended coolant

Testing Coolant Condition and Strength Used conventional coolant should have a pH level of at least 9 Extended life should be at least 7.5

Testing Coolant Condition and Strength

Coolant Density Testers Two ways to test density: Hydrometer Compares weight of ethylene glycol to weight of pure water Refractometer Measures how much light can be bent by coolant

Coolant Density Testers

Coolant System Air Bleeding All air must be removed from system Jack front of car up as high as it will go Some vehicles have bleed screws Remove heater hose to bleed air Use special air removal tool

Cavitation Causes of formation of air bubbles in coolant Coolant boiling Air in coolant Suction restriction Over pumping Vibration of cylinder wall during combustion