Cooling System

Keeps the engine from overheating

Components of the Cooling System

Components of the Cooling System

Did you ever wonder how the cooling system works?  Let me explain it to you.

The components of the cooling system are:

  • Radiator
  • Heater core
  • Temperature control valve
  • Temperature knob
  • Coolant
  • Thermostat
  • Thermo sensor
  • Water pump
  • Temperature gauge
  • Temperature sensor
  • Reservoir
  • Radiator Cap

The RADIATOR is the most important part of the cooling system to keep your engine running cool. The radiator is usually made of brass and/or plastic. The brass inner core of the radiator is usually black so that it transfers the heat of the COOLANT to the metal fins in the airflow on the outside of the radiator. The top and bottom tanks of the radiator serve to attach the hoses from the radiator to the engine. Sometimes several rows of cooling fins on the radiator are devoted to a transmission or engine cooler.

The HEATER CORE is a small radiator type device located under the dashboard in the passenger compartment. The TEMPERATURE KNOB on the dash controls the TEMPERATURE CONTROL VALVE in the engine compartment. As the knob is turned toward the warmer setting, the temperature control valve opens, allowing coolant from the engine to circulate through the heater core, warming the interior of the car. When the car is cold, just after startup, the coolant circulates from the engine to the heater core without circulating through the radiator. The THERMOSTAT is closed until the coolant from the engine reaches a higher temperature. This allows rapid heating of the interior of the vehicle. When the temperature knob is turned toward the cold side, the temperature control valve closes, allowing cool air from the air conditioner system to flow through the heater core, cooling the interior of the vehicle.

The WATER PUMP serves to circulate the coolant around the cooling system. The water pump is usually driven by a belt on the crank pulley and turns about the same RPM as the engine.

The thermostat is in the engine in line with the radiator hose. The thermostat is closed when the engine is cold and circulates coolant only through the engine and heater core to allow use of the defroster as quickly as possible. It opens slowly depending on the temperature of the coolant. The thermostat is fully open at 180 degrees. The thermostat serves to keep the coolant at a constant temperature by closing slightly when the engine cools (such as when cruising on the freeway). This slows the passage of coolant through the radiator allowing the engine to maintain a constant temperature.

The TEMPERATURE GAUGE is attached to a SENSOR on the engine block. This sensor varies electrical resistance as it heats up allowing the accurate monitoring of engine temperature.

The THERMO SENSOR is an electrical device that makes contact when it reaches a preset temperature. The thermo sensor is installed into the bottom of the radiator or the engine block and monitors coolant temperature. The thermo sensor controls the operation of the fans on the radiator. When the coolant reaches a preset temperature, it turns on the cooling fans on the radiator. Since this circuit has power even when the ignition switch is turned off, the radiator fan sometimes comes on after the engine is off, depending on the temperature of the coolant. It can run for up to fifteen minutes because when you turn off the engine, the coolant no longer circulates with the water pump. The coolant in the engine gets hot enough to open the thermostat. This causes the coolant to circulate to the radiator because the coolant there is not as hot. When this cooler coolant reaches the thermostat, it closes. This coolant in the engine absorbs the heat of the engine again and opens the thermostat again. This process continues for about 15 minutes until the coolant temperature falls below the temperature of the thermo sensor.

The cooling system on most new cars is a sealed system. All air in the cooling system is allowed to escape when filling the radiator. Any leak will cause loss of coolant and overheating. A quick look at the temperature gauge occasionally will save you a lot of trouble, A quick look for green residue where you park will avert a problem.

Occasionally, if the engine overheats, the headgasket could fail causing water to be ingested into one or more cylinders. The engine becomes very difficult to start because the water causes “hydro lock”. The water doesn’t compress and if starting is continued, the engine will be considerably damaged. Hydro lock can occur also if the car is submerged under water for more than five minutes. The water seeps past the air filter into the cylinders. DO NOT…I repeat…DO NOT attempt to jump-start the battery with another car. The spark plugs must be removed and the engine flushed out before starting the engine can be attempted.

An overflow bottle is used as a RESERVOIR for coolant as it expands and contracts. Because coolant contracts when hot and expands when cool, the hot radiator creates a vacuum pulling in coolant from this reservoir. As the radiator cools, the coolant returns to the reservoir for future use. The reservoir bottle tends to collect the residue of the cooling system. This is why the reservoir bottle is cleaned at every major service when the coolant is changed.

For the entire system to work properly, the RADIATOR CAP must seal the cooling system.

…and that’s the way the cooling system works!!

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