2PurposeNormal operation produces heat that must be carried away by coolantCooling system transfers heat to cooler outside air when engine is hot.Cooling system keeps heat in the engine when engine is not warm enough.Modern cooling systems are designed to maintain an even temperature of about 180 to 230°F (82 to 113°C).
3Cooling System Operation System design removes 35% of total heat.If not equipped with factory A/C, cooling system is usually not able to handle additional heat load of aftermarket units.
4Components COOLING SYSTEM COMPONENTS Water Pump Cooling Fan Radiator Pressure CapThermostatClamps and hosesOverflow tank
5Water Pumps Centrifugal Type Water Pump. Inlet comes from bottom of Radiator.Outlet is through impeller to engine.Water Pump Replacement can be due to leaks or bearing failure.Transfer pump parts and use correct gaskets.
6Weep Hole Coolant will often leak out of the weep hole. This indicates the shaft seals in the water pump have failed.Water pump replacement will be required.
7Water PumpsWater pumps can be driven off of the serpentine belt, the timing belt, or the camshaft.When driven off of the timing belt, most technicians suggest replacement when replacing the timing belt.
10Radiators Allows for heat to move from coolant to the outside air. Cooler air flowing through the radiator cools the coolant.Most radiators about sq. feet.Can have multiple cores to increase area.Two types… - Cross flow - Down flow
13Radiators Many radiators will have oil coolers built into them. These can be for the engine oil or the ATF.Should either of these crack, oil could get into the coolant and coolant into the oil.
14Coolant ExpansionRadiator pressure results from the expansion of the coolant as the engine warms up.A small amount of air used to be kept in the radiator to allow for this expansion.Since air leads to rust and corrosion, the radiator needs to be filled completely with coolant.The pressure cap and coolant reservoir work together to allow for this expansion.
15Pressure CapThe upper gasket prevents coolant from escaping to the outside. The lower gasket keeps a pressure in the radiator. The cam lock pushes the two gaskets against the sealing surfaces when the cap is installed. The safety stop prevents the cap from being opened too quickly.
16Pressure CapPressurizing a liquid increases the boiling point of that liquid.Cooling systems are pressurized so that the boiling point of the coolant is raised.Many cooling systems are pressurized to 15 psi.The coolant’s boiling point increases about 3° F for each psi increase in pressure.
17Pressure CapThe pressure cap allows the pressure to build, and release past a specified point.Equipped with Vacuum and Pressure ValveUsed to raise Pressure in system
20Pressure CapThe pressure cap also improves the operation of the water pump.By keeping the radiator pressurized, the water pump has a constant supply of coolant to draw from.If pressure became too low, the coolant would boil and the water pump would draw only air.
21Overflow Tank Contains reserve coolant. When cap releases coolant due to coolant expansion, coolant goes to overflow tank.When cooling system cools off and creates a vacuum, coolant is pulled from overflow tank.
23Overflow TankSome closed cooling systems do not have a cap on the radiator.The overflow tank is pressurized with the rest of the cooling system.The coolant level will be checked in the overflow tank.
24Pressurized TanksSystems with a pressurized overflow tank keep a small amount of air in the tank.This allows the coolant to expand and compress the air.Most tanks like this will have a pressure cap on the tank and no cap on the radiator.
27Opening a Hot SystemSlowly turn the cap with a rag and do not turn it past the safety lock.
28Thermostat Speeds up engine warm up. Regulates flow and temperature of engine coolant.Most are on the outlet side of coolant flow.Maintains optimum engine operating temperature for best emissions and economy.
29Thermostat Thermostat temperature is the opening temperature Thermostat should be fully open 20°F above opening temperature195°F thermostat = fully open at 215°F180°F thermostat = fully open at 200°F
30ThermostatThe thermostat contains a wax pellet on the engine side of the thermostat.Wax melts and expands when engine heats up.As the wax expands, it overcomes spring pressure and opens the valve.
36PowerGrip ClampPowerGrip clamps are larger than the hose and must be heated to shrink and seal the hose.
37Hoses Preformed hoses are made specifically for an application. Flex hoses are used for a variety of applications.Some lower radiator hoses contain a spring to prevent them from collapsing due to water pump suction.
38Coolant Flow The water pump pumps coolant through the block. If the thermostat is closed, coolant flows through the block, heater core, and the thermostat bypass.The bypass leads back to the water pump.There will be no flow through the radiator when the thermostat is closed.
39ThermostatWhen the thermostat is closed, coolant is directed back into the block through the bypass passage.
40Coolant BypassSome thermostats are designed to block off the bypass passage when they are open.
43Coolant FlowWhen the thermostat is open, coolant is then allowed to flow from the block to the upper part of the radiator.The coolant is then cooled in the radiator.The water pump draws the coolant out of the bottom of the radiator so that it can then be circulated throughout the block to cool the engine.
44Water JacketsWhen an engine cylinder block and head are cast, cavities called water jackets are formed around the cylinder walls and combustion chambers.These water jackets allow coolant to circulate around the very hot areas, including the exhaust valve seats, as well as the relatively cooler areas of the lower cylinders.The coolant absorbs heat from the hot areas and transfers this heat to the colder areas in the engine or radiator.
47Coolant FlowSome manufacturers position the thermostat on the inlet side of the water pump.As the cooled coolant hits the thermostat, the thermostat closes until the coolant temperature again causes it to open.This reduces thermal cycling (expanding and contracting of the metal).Thermal cycling can damage aluminum engine components.
48A modern style cooling system showing how the coolant flows through the block first, then through the cylinder head, and finally through the radiator after the thermostat opens.
49Block HeatersBlock heaters are small, electrical-resistance heater units that can be mounted in the block.These heaters are plugged into ordinary 110-volt ac outlet and are used in very cold areas to warm an engine while it is shut off.Block heaters provide easier engine starting and faster warm-up, especially for diesels.
50Block HeatersTypical block heaters install in one of the core plug holes.
51Aftermarket Block Heaters Aftermarket block heaters generally should not be installed in late model vehicles.The computer checks the ambient air vs. the coolant temperatures after sitting for several hours.If the two disagree, the MIL will illuminate and a DTC will set.