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Cooling System

Photo of a La Palma Mobile Mechanic service tech replacing a failed car radiator for a customer in Artesia, California.

La Palma Mobile Mechanic technicians make cooling system repairs often and having an understanding of exactly how the cooling system functions allow us to zero in on the precise problem so the correct repair can be made.  For cooling system problems or other engine repairs, call us and get your problem fixed fast.

Cooling System Components

        • Radiator
        • Water Pump
        • Coolant
        • Thermostat
        • Cooling Fan

Your car's cooling system works by moving liquid coolant through channels in the engine to dissipate heat. When the coolant moves through these channels, it gets hot from the engine's many combustions.  The hot coolant then makes its way through a radiator hose to the radiator.  There, it flows through thin tubes in the radiator and is cooled by the air stream blowing past the radiator fins.  Once cooled, the coolant is pushed back through the engine by the water pump to once again absorb more heat.


The radiator is the heart of the cooling system and is normally comprised of compacted aluminum tubes with attached aluminum fins.  The fins weave back and forth and take a rectangular form.  As air moves over the radiator, the fins transfer the heat from the tubes into the airflow, to be transported away from the automobile.  Done on large scale, with many tubes and fins, the radiator cools the super hot coolant circulating through your engine.  On each end of the radiator core is a tank, generally made from vinyl, which covers the ends of the radiator.

Water Pump

The water pump is a simple device that keeps the coolant moving throughout an engine  It's generally mounted on the front part of the engine and works whenever the motor is operating.  The water pump is usually powered by a fan belt or a serpentine belt, but can sometimes be powered by the timing belt or camshaft.

It is composed of a casing, typically made from cast iron or cast aluminum along with an impeller mounted onto a spinning shaft using a pulley attached to the rotating shaft on the exterior of this pump body.  A seal retains fluid from draining from the pump casing beyond the turning shaft.  The impeller utilizes centrifugal force to suck the coolant in by the lower radiator hose and then move it under pressure through the engine block's water passages.  There's a gasket to seal the water to the engine block and stop the flowing coolant from draining outside where the pump is connected to the block.

Coolant / Antifreeze

Engine coolant is merely a combination of antifreeze, deionized water, corrosion inhibitors, and dyes.  Possessing the right mixture is essential as it prevents corrosion of the heating system parts, and also increases the boiling point and reduces the freezing point of the coolant.

Engine coolants use ethylene glycol and propylene glycol which raise the boiling point and lower the freezing point of the coolant.  Water is added to dilute the coolant because the glycol doesn’t get rid of heat as well on its own.  Most engine coolants come premixed because the mixture of half water, half coolant is recommended.  Coolant should be changed periodically because the corrosion inhibitors in them will break down over time.


The thermostat is just a valve that measures the temperature of the coolant and, at a certain temperature, opens to allow it to flow through the radiator.  If the coolant is not hot enough, the flow into the radiator is obstructed and the fluid is bypassed back into the engine.  This system allows the coolant to keep moving throughout the engine to balance the temperature and also prevent hot spots.  Because flow into the radiator is obstructed, the engine will reach working temperature quickly on a chilly day, and allow the heater to start providing hot air to the interior more quickly.

Cooling Fan

The radiator cooling fan is a significant part of the cooling system. Though a fan is not really necessary while a vehicle is traveling down the highway, it is very important when driving slow or when you're stopped and the engine is running. In earlier times the fan was attached to the motor and was powered by a fan belt.  The speed of this fan was proportional to the rate of the engine.  This kind of system sometimes caused excess noise as the car accelerated.  As the engine sped upward, a rushing fan noise could be heard.  To calm down things and put less of a drag in the motor, a fan clutch was designed to disengage the fan when it wasn't needed.

Today, electric fans are used that are computer-controlled, quiet, and very efficient.


There are numerous rubber hoses which compose the pipes to connect the parts of the cooling system.  The principal hoses are called the upper and lower radiator hoses. Both of these hoses are approximately two inches in diameter and also guide flow between the engine and the radiator.  Two extra hoses, called heater hoses, provide hot coolant from the engine into the heater core.  These hoses are approximately 1 inch in diameter.