Chevrolet Equinox Service Manual: Cooling System Description and Operation Engine Cooling

Engine Coolant Indicator(s)

LOW COOLANT LEVEL

The IPC illuminates the low coolant warning indicator whenany of the following occur:

The BCM detects a low coolant level condition for at least30-seconds. The IPC receives a class 2 message from theBCM requesting illumination.The IPC performs the displays test at the start of eachignition cycle. The indicator illuminates for approximately3-seconds.Coolant Heater

The optional engine coolant heater (RPO K05) operates using110-volt-AC external power and is designed to warm thecoolant in the engine block area for improved starting in very coldweather −29°C (−20°F). Thecoolant heater helps reduce fuel consumption when a cold engine iswarming up. The unit is equipped with a detachable AC power cord. Aweather shield on the cord is provided to protect the plug when notin use. The power cord has a thermal element in the cord end thatdoes not allow current to the heater until the ambient temperaturereaches 0°F or −18°C.

Cooling System

The cooling system's function is to maintain an efficientengine operating temperature during all engine speeds and operatingconditions. The cooling system is designed to remove approximatelyone-third of the heat produced by the burning of the air-fuelmixture. When the engine is cold, the coolant does not flow to theradiator until the thermostat opens. This allows the engine to warmquickly.

Cooling Cycle

Coolant flows from the radiator outlet and into the waterpump inlet. Some coolant flows from the water pump, to the heatercore, then back to the water pump. This provides the passengercompartment with heat and defrost capability as the coolant warmsup.

Coolant also flows from the water pump outlet and into theengine block. In the engine block, the coolant circulates throughthe water jackets surrounding the cylinders where it absorbsheat.

The coolant then flows through the cylinder head gasketopenings and into the cylinder heads. In the cylinder heads, thecoolant flows through the water jackets surrounding the combustionchambers and valve seats, where it absorbs additional heat.

From the cylinder heads, the coolant flows to the thermostat.The flow of coolant will either be stopped at the thermostat untilthe engine reaches normal operating temperature, or it will flowthrough the thermostat and into the radiator where it is cooled. Atthis point, the coolant flow cycle is completed.

Efficient operation of the cooling system requires properfunctioning of all cooling system components. The cooling systemconsists of the following components:

Coolant

The engine coolant is a solution made up of a 50-50 mixtureof DEX-COOL and suitable drinking water. The coolant solutioncarries excess heat away from the engine to the radiator, where theheat is dissipated to the atmosphere.

Radiator

The radiator is a heat exchanger. It consists of a core andtwo end tanks. The aluminum core is a tube and fin crossflow designthat extends from the inlet tank to the outlet tank. Fins areplaced around the outside of the tubes to improve heat transfer tothe atmosphere.

The inlet and outlet end tanks are a molded, hightemperature, nylon reinforced plastic material. A high temperaturerubber gasket seals the end tank flange edge to the aluminum core.The end tanks are clamped to the core with clinch tabs. The tabsare part of the aluminum header at each end of the core.

The radiator utilizes a drain cock for coolant recoveryduring service. The drain cock is located at the bottom of theright hand or left hand end tank, depending on the powertrainoption in the vehicle. The drain cock unit includes the drain cockand drain cock seal.

The radiator removes heat from the coolant passing throughit. The fins on the core transfer heat from the coolant passingthrough the tubes. As air passes between the fins, it absorbs heatand cools the coolant.

Pressure Cap

The pressure cap seals the cooling system. It contains a blowoff or pressure valve and a vacuum or atmospheric valve. Thepressure valve is held against its seat by a spring, which protectsthe radiator from excessive cooling system pressure. The vacuumvalve is held against its seat by a spring, which permits openingof the valve to relieve vacuum created in the cooling system as itcools off. The vacuum, if not relieved, might cause the radiatorand/or coolant hoses to collapse.

The pressure cap allows cooling system pressure to build upas the temperature increases. As the pressure builds, the boilingpoint of the coolant increases. Engine coolant can be safely run ata temperature much higher than the boiling point of the coolant atatmospheric pressure. The hotter the coolant is, the faster theheat transfers from the radiator to the cooler, passing air.

The pressure in the cooling system can get too high. When thecooling system pressure exceeds the rating of the pressure cap, itraises the pressure valve, venting the excess pressure.

As the engine cools down, the temperature of the coolantdrops and a vacuum is created in the cooling system. This vacuumcauses the vacuum valve to open, allowing outside air into thesurge tank. This equalizes the pressure in the cooling system withatmospheric pressure, preventing the radiator and coolant hosesfrom collapsing.

Surge Tank

The surge tank is a plastic tank that the pressure cap mountsonto. The tank is mounted at a point higher than all other coolantpassages. The surge tank provides an air space in the coolingsystem. The air space allows the coolant to expand and contract.The surge tank also provides a coolant fill point and a central airbleed location. During vehicle use, the coolant heats and expands.The coolant that is displaced by this expansion flows into thesurge tank. As the coolant circulates, air is allowed to exit. Thisis an advantage to the cooling system. Coolant without bubblesabsorbs heat much better than coolant with bubbles.

Air Baffles and Seals

The cooling system uses deflectors, air baffles and air sealsto increase cooling system capability. Deflectors are installedunder the vehicle to redirect airflow beneath the vehicle andthrough the radiator to increase engine cooling. Air baffles arealso used to direct airflow through the radiator and increasecooling capability. Air seals prevent air from bypassing theradiator and A/C condenser, and prevent recirculation of hot airfor better hot weather cooling and A/C condenserperformance.

Water Pump

The water pump is a centrifugal vane impeller type pump. Thepump consists of a housing with coolant inlet and outlet passagesand an impeller. The impeller is a flat plate mounted on the pumpshaft with a series of flat or curved blades or vanes. When theimpeller rotates, the coolant between the vanes is thrown outwardby centrifugal force.

The impeller shaft is supported by one or more sealedbearings. The sealed bearings never need to be lubricated. Greasecannot leak out, dirt and water cannot get in as long as the sealis not damaged or worn.

The purpose of the water pump is to circulate coolantthroughout the cooling system. The water pump is driven by thecrankshaft from the drive belt.

Thermostat

The thermostat is a coolant flow control component. Itspurpose is to help regulate the operating temperature of theengine. It utilizes a temperature sensitive wax-pellet element. Theelement connects to a valve through a small piston. When theelement is heated, it expands and exerts pressure against the smallpiston. This pressure forces the valve to open. As the element iscooled, it contracts. This contraction allows a spring to push thevalve closed.

When the coolant temperature is below the rated thermostatopening temperature, the thermostat valve remains closed. Thisprevents circulation of the coolant to the radiator and allows theengine to warm up. After the coolant temperature reaches the ratedthermostat opening temperature, the thermostat valve will open. Thecoolant is then allowed to circulate through the thermostat to theradiator where the engine heat is dissipated to the atmosphere. Thethermostat also provides a restriction in the cooling system, afterit has opened. This restriction creates a pressure difference whichprevents cavitation at the water pump and forces coolant tocirculate through the engine block.

Transmission Oil Cooler

The transmission oil cooler is a heat exchanger. It islocated inside one of the radiator end tanks. The transmissionfluid temperature is regulated by the temperature of the enginecoolant in the radiator. The transmission oil pump, pumps the fluidthrough the transmission oil cooler line to the transmission oilcooler. The fluid then flows through the cooler where the enginecoolant absorbs heat from the fluid. The fluid is then pumpedthrough the transmission oil cooler return line, to thetransmission.