Understanding How an Auto Cooling System Works

February 17, 2012

Learn how auto cooling system parts--the water pump, thermostat, radiator, cooling fan and hoses--work together with coolant to prevent overheating.

Maintaining an Auto Cooling System

Your car's engine produces incredibly high levels of heat and the cooling system is essential in cooling your car's engine enough to avoid damaging the parts inside it. The engine creates power to propel your vehicle by a combustion process that literally involves creating thousands of controlled explosions caused by igniting the fuel and air mixture inside the engine.

Without a cooling system, your engine would quickly reach temperatures that would damage most of its components. Every car's engine is designed to function in a very specific temperature range, usually between 160 and 190 degrees. Any colder and the engine's oil is too thick to move efficiently, and the moving parts in the engine don't get lubricated properly. Any hotter and the engine is vulnerable to being damaged by heat. Heat damage is one of the leading causes of engine failure. Excessive heat can cause cracking in the engine block, cylinder head and manifold as well as accelerated wear to bearing surfaces in the engine bearings and valve train (The system that allows your engine to "breathe" and includes the camshaft, valves and lifters).

Your car's cooling system is a complex system consisting of several different parts and subsystems.

Coolant
The coolant, or radiator fluid, used in your car's cooling system is perhaps the most vital part of the system. Coolant flows throughout the entire cooling system, dissipating the heat created in the internal combustion engine. The radiator fluid is usually a glycol based liquid that is then mixed with water. It is specifically designed to retain important properties while it is in the demanding environment of a vehicle's engine. The additives included in engine coolant help it transfer heat effectively, keep it from boiling and over-pressurizing the cooling system, or freezing in cold weather and damaging the engine (hence the term antifreeze).

Water Pump
The water pump is a mechanical pump pushes the coolant through the radiator and your car's engine. Because the water pump is mechanical, it requires a belt to turn the rotor. Some vehicles use a dedicated radiator fan and belt for this purpose and others use a belt connected to other components in the vehicle such as air conditioning and power steering. This type of belt is commonly referred to as the serpentine belt.

The water pump provides the pressure that moves the coolant through the engine and radiator. It accomplishes this by using a specially designed blade called an impeller that resembles the propeller on a boat or a tiny water-wheel. Once the coolant is pushed past the water pump, it moves through hundreds of tiny passages built into all areas of the engine, where it pulls heat out of the metal parts of the engine. Once it has done its job, the heated coolant moves through the thermostat and back into the radiator.

Thermostat
The thermostat detects your car's operating temperature. It is also designed to regulate the flow of coolant from your radiator to your engine. When your engine reaches a certain temperature the thermostat releases the flow of coolant and when the engine is cooler, it restricts it.

Radiator
The radiator is a square or rectangular shaped metal box that fits in front of your engine. It draws in cooler ambient air from the outside to help cool the radiator fluid. A radiator is usually made out of a metal such as aluminum, or in some cases copper, that conducts heat very well. It includes a series of tubes and fins where the fluid passes through and is cooled by air drawn into the radiator.

Hot coolant flows into the radiator and is into tiny passages connected to the small metal fins. As the coolant moves through the passages, heat is transferred into the fins. Air is forced through the spaces between the metal fins by the motion of the vehicle or the engine's fan, and heat is radiated into the air (hence the radiator's name) and away from the engine. Once the coolant has gone through this process, its temperature is drastically reduced. Now it is ready to pull the heat out of the engine, and it is moved into the engine towards the water pump.

Radiator Cooling Fan
The radiator cooling fan is usually located directly behind the radiator itself. Its function is to pull air through the radiator when the vehicle is operating at slower speeds. It may be mechanical and driven by a belt, or it may be electric and controlled by the thermostat.

Hoses
Your car's cooling system utilizes several hoses for transferring the coolant from one part of the cooling system to another. These hoses are usually connected to different parts of the cooling system using hose clamps or clips. In order for the hoses to function correctly, they should always be free from cracks or cuts that may cause coolant to leak.

Automotive Cooling System Repair Costs for Common Problems

Repair costs for cooling system repairs are determined by the model, year and vehicle manufacturer. Moreover, there are differences between rear wheel drive vehicles, front wheel drive vehicles, trucks, SUVs and different sized passenger vehicles. You will sometimes pay a higher cost for the same type of repair simply because you drive a luxury vehicle, whose repair parts are higher priced.

Labor rates can fluctuate from $75 to $125 per hour, and can make up the bulk of the cost for a cooling system repair. Typically, the more exclusive or luxurious the make of the vehicle, the higher the labor rate and part costs.

Repair Time and Average Labor Costs of Typical Cooling System Problems

Since the cost of repair parts are tied to the type of vehicle you own, the best way to determine the cost for a repair job is to compare hourly labor rates and labor time to fix the problem. Furthermore, some shops will charge a higher fee for miscellaneous shop supplies, and sell you new hose clamps whether you needed them or not.

  • Radiator replacement:2.6 to 3.2 hours ($260 to $320)
  • Thermostat (and gasket) replacement:1.0 to 1.8 hours ($100 to $180)
  • Water pump (and gasket) replacement:1.8 to 2.5 hours ($180 to $250)
  • Radiator hose:0.75 to 2.0 hours (can also be a time difference between upper hose and lower hose) ($75 to $200)
  • Cooling system flush:1.0 to 2.0 hours ($100 to $200)
  • Radiator cooling fan (assembly): 1.1 to 2.5 hours ($110 to $250)
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