The Cooling System

Vocabulary Thermostat bypass 11.Hoses-clamps Sending unit 12.Coolant-ethylene Fan clutch 13.Corrosion Heater core 14.Temperature gauge Water-cooled 15.Closed cooling system Air-cooled 16.Radiator cap Water pump-impeller 17.Thermostat “V” belt/serpentine belt Radiator Radiator fan shroud

At 2500 rpm & medium load a 350 cid At 2500 rpm & medium load a 350 cid. V-8 engine produces enough cooling system heat in 15 minutes to heat three 2000 square foot houses in Chicago during January.

Purpose of cooling system The purpose of the cooling system is to do three things: To maintain the most efficient operating temperature within the engine. To remove excess heat from the engine. To bring the engine up to operating temperature as quickly as possible.

Wrong Eng. Temp. If the engine temperature is too high Overheating of lubricating oil. This will result in the lubricating oil breaking down. Overheating of the parts. Cylinder wall, piston & bearing scuffing. Cylinder head warpage & head gasket failure. Engine temp should never exceed 230 degrees F.

Wrong Eng. Temperature If the engine temperature is too low, various problems will occur: Poorer fuel mileage. Increases in carbon buildup. Increases in varnish and sludges within the lubrication system. excessive exhaust emissions. excessive engine wear.

Heat Transfer The cooling system works on the principles of heat transfer. Heat will always travel from a hotter to a cooler object. Heat transfers in three ways: conduction, convection, and radiation. Conduction is defined as transfer of heat between two solid objects. In this picture, heat must be transferred from the valve guide.

Types of Cooling System Engine manufacturers commonly use two types of cooling systems. These are the air-cooled and liquid cooled systems. Air-cooled engines Air cooled engines have fins or ribs on the outer surfaces of the cylinders and cylinder heads. The fins increase the surface area of the object which, in turn, increases the amount of convection and radiation available for heat transfer. The heat produced by combustion transfers from the internal parts of the engine by conduction to the outer fins.

Types of Cooling Systems Liquid-cooled Engines In the liquid-cooled engine, the heat from the cylinder is transferred to a liquid flowing through jackets surrounding the cylinders. The liquid then passes through a radiator. Air passes through the radiator removes the heat from the liquid to the air. Liquid cooling systems are designed to maintain a coolant temperature of 180-210 degrees F.

Types of Cooling Systems Liquid-coolant Flow When the vehicle is started the coolant pump begins circulating the coolant. The coolant goes through the cylinder block from the front to the rear. The coolant circulates around the cylinders as it passes through the cylinder block.

Types of Cooling Systems The coolant then passes up into the cylinder head through the holes in the head gasket. It then moves forward to the front of the cylinder head through internal passages. These passages permit cooling of high-heat areas such as the spark plug and exhaust valve areas. As the coolant leaves the cylinder head, it passes through a thermostat on the way to the radiator.

Parts of Liquid-Cooling Sys.

Water Jackets Open spaces within the cylinder block and cylinder head where coolant flows. Water jackets are designed to allow coolant flow to the right spots so that maximum cooling can be obtained.

Water Pump The purpose of the water pump is to circulate the water through the cooling system. The pump is located on the front of the engine. In most vehicles it is driven by a belt that is attached to the crankshaft. As the crankshaft turns the fan belt turns the pump, causing coolant to be circulated.

Water Pump The pump consist of a housing, a bearing on a shaft, the impeller, and seal. The housing has a coolant inlet and outlet. The seal is used to keep the water inside the pump. The bearing is used to support the shaft on which the impeller rides. The Impeller causes the water to circulate.

Water Pump

Thermostat One of the most important parts of the cooling systems. The purpose of the thermostat is to keep the engine coolant at most efficient temperature. The thermostat is used to bring the coolant temperature up to operating as quickly as possible. It is designed to sense the temperature of the coolant.

Thermostat A wax pellet material within the thermostat expands and causes the mechanical motion that opens the thermostat. This allows the coolant to pass through the radiator.

Thermostat The thermostat is usually placed near the front of the engine. This picture shows how the thermostat is placed with the thermostat housing cover.

Radiator The purpose of the radiator is to allow fresh air to reduce the temperature of the coolant. This is done by flowing the coolant through tubes. As the coolant passes through the tubes air is forced around the tubes. This causes a transfer of heat from the hot coolant to the cooler air. This is called heat exchanged. In this case, heat is exchanged from a liquid, the coolant, to air. this is called a liquid-to air heat exchanger.

Modern radiator Fan Shroud

Radiator This picture shows an internal diagram of a typical radiator core. Coolant flows through the tubes, and air flows through the air fins. Radiators are made of several parts. The fins and tubes are called the core.

Radiator The core and fins on the radiator are made of brass, copper, or aluminum or some combination of those metals. There are also inlet and outlet tank. These tanks hold the coolant before it goes into the radiator core or back into the block. The inlet tank has a hose connection to allow coolant to flow from the engine to the radiator. The outlet tank has a hose connection to allow coolant to pass back to the engine.

Radiator hoses Radiator hoses transport coolant from engine to radiator & back

cooling sys - Part 2

Radiator Pressure Cap Pressure caps are designed to: Increase the pressure on the cooling system Reduce cavitation Prevent or reduce surging It is important to put pressure on the cooling system. Radiator pressure caps are typically near 15 pounds per square inch. As pressure increases the boiling point of the coolant also increases. ( about 3 degrees for each 1 psi increase)

Pressure Cap During operation a spring holds desired pressure inside the cooling system, the vacuum valve is pulled down and opened as system cools. spring

Expansion Tank (closed system) Cooling systems with expansion tanks are also called closed cooling system. They are designed to hold any coolant that passes through the pressure cap when the engine is hot. This picture shows a expansion tank.

Fan The fan draws air through the radiator for cooling during low vehicle speed and idle operation. It is not needed at faster vehicle speed because air is pushed through the radiator by the vehicle movement. The fan can absorb up to 6% of the engine horsepower. Clutch fan slips at higher engine speeds

Electric Fan Relay In order for the fan motor to start, the engine cooling fan relay must operate to close the switch. When this is closed the fan switch will turn on. The engine coolant temperature switch closes because the engine temperature increased to a certain point.

Coolant Temp. Indicators As the temperature of the coolant increases to a certain level, the heat from the engine causes an electrical circuit to close inside the switch. This switch connects a warning light on the dashboard to ground – completing a circuit from the battery & lighting the light..

Coolant Temp. Indicators A second type of temperature indicator reads the actual coolant temperature and displays this on the dashboard of the vehicle.

Fan Belts Fan belt is used to turn the water pump and the fan. Using the V-type belt produces a large area of contact. The flat serpentine belt is about 1 inch wide and has several grooves on one side and is flat on the other. One Serpentine belt is often used to run all the engine accessories.

Serpentine belt

Belt routing Diagram

Serpentine belt routing

Types of coolant Green “older cars” Orange “Dex cool - GM” Yellow “ford” Always check manufactures recommendations . Coolants of different types should never be mixed!!!

50 – 50 mix of Dex-Cool Pre mixing coolant & water

Coolant Prevents Freezing Increases boiling point Lubricates water pump Stops corrosion

Coolant Hazardous Waste Antifreeze is considered hazardous waste product. It is harmful to people and to the environment. the procedures and laws for disposing of antifreeze vary from state to state. The best method to dispose of antifreeze is to recycle the product. Depending on the city and region, there are various private and public organizations that collect and recycle antifreeze.

Coolant Freezing Points when 100% water is used, the freezing point is 32 degrees F. when 25% antifreeze and 75% water are used, the freezing point of the coolant is about -10 degrees F. A 50% water 50% anti freeze mix will protect to around -50 degrees F. This is all the protection needed in most areas of the united states.

Coolant Boiling Points Boiling point of a fluid is the temperature at which the fluid becomes a vapor. Any coolant that becomes a vapor has very poor conduction and convection properties. So it is necessary to protect it from boiling.

Coolant Corrosion can be produced several ways: Direct attack means the water in the coolant is mixed with oxygen from the air. This process can produce rust particles, which can damage water pump seals and cause increase leakage. Electromechanical attack is a result of using different metals in an engine. In the presence of a coolant, different metals may set up an electrical current in the coolant. If this occurs, one metal may deteriorate and deposit itself on the other metal.

Cooling system pressure check

Safety precautions Remember that a hot cooling system is approx 210 degrees F or hotter. Touching the coolant or spilling the coolant on your body may cause serious injury. When working with coolant, for example when replacing the water pump or thermostat, you may spill some coolant on the floor. The antifreeze in the coolant causes it to be very slippery. Immediately wipe up any coolant that spills.

Safety precautions Always wear proper clothing and eye protection when using coolant additives to remove silicate and calcium deposits; they may be very corrosive. When working on the fan, water pump, or belts, make sure the engine ignition system is off or the battery is disconnected or both. Whenever the vehicle is running always keep fingers, tools, and clothing away from the moving fan.

Safety precautions When working on the water pump, fan, or belts, be careful not to scrape your knuckles against the radiator. Never remove the pressure cap when the engine is hot. Removing the pressure cap releases the pressure on the cooling system. This reduces the boiling point of the coolant. The coolant will then boil violently and burn or injure a persons’ hands or face.

Safety Precautions When using a chemical cooling system cleaner, be careful not to get the chemical in your eyes or on your skin. Keep antifreeze away from children and animals. Antifreeze has a sweet taste, and, if consumed it could lead to death in as little as 24 hrs. if antifreeze is ingested, see a doctor immediately.

Service Common specification: Belt tension Cooling system capacity New 165lbs. Used 100lbs. Cooling system capacity Without air conditioner (A/C) 15.3quarts With air conditioner 15.9quarts Radiator cap relief pressure 16lbs. Thermostat opening temperature 195°F

R&R Water Pump Make sure the engine is cool or at room temperature. Remove the radiator cap Drain the coolant from the radiator and cylinder block. Remove the belts by loosening the appropriate components on the belt. On some engines the radiator may have to be removed to get at the water pump.

Remove the fan if its driven by the water pump. Remove the bolts holding the water pump to the engine cylinder block Scrape the old gasket completely off the block Replace the old gasket with a new gasket. Replace the water pump with a new or rebuilt pump.

Reverse the previous procedure to complete assembly. Before installing the belt, check the inside surface for wear. Twist the belt slightly to see if there are any cracks on the inside surface. Always check the reinforcement springs inside the lower radiator hose. If the lower hose is replaced, make sure the spring is not deformed, missing, or out of position. Check the front of the radiator. Keep the front clean and free of dirt, bugs, and other debris.

When finished remove the pressure tester and replace the pressure cap. After all the parts have been inspected and replaced, add the coolant back into the cooling system. Extra antifreeze may have to be added. Check the fan belts. Always check the fan belts for wear and correct tension. Tension on the fan belt can be checked by using the gauge. After all parts have been inspected and reassembled run the engine and pressure test for leaks again. When finished remove the pressure tester and replace the pressure cap.

Good luck on your unit test!