Cooling Systems

The most important system in prolonging the correctly working engine in your vehicle is what keeps it running at the most efficient operating temperature. Most people think of the radiator but here are some details about what works with the radiator to keep the engine cool. It is extremely important to regularly clean out the cooling system. As scale forms, heat convection transfer and dissipation is greatly reduced. Yes, there is a range of acceptable operating temperatures for a given engine, not too cold and not too hot, but for us in the desert, we are already starting near the top end of the near hot range. The cooling system can contain from 2 to 20 gallons of liquid, depending on the vehicle or system. The average is somewhere around 8 gallons. While in description and function, cooling systems appear to be somewhat simple in definition, objective and operation. However, in many of the modern vehicles, they are both monitored and controlled by computers.

Cooling System and Radiator
The heart of the cooling system is the radiator. Other components include the water pump, heater, one or more sensors, thermostat, hoses, belts, overflow reservoir, and coolant, water or a combination of both. The radiator is the storage facility for the liquid that cools the engine. It is also the point where that liquid is "recycled" to a lower temperature by having air flow across the coils it is in, in order to take away the heat. Within the coils, the water flows with air passing over the outside of the coils, carrying away heat, if the coils become clogged or reduced in the amount of liquid they can handle, efficiency is hampered. Overheating and pressure cause problems. Regularly, the radiator and system need to be cleaned out of old liquid (flushed), boiler scale, rust and other impurities, then refilled with a new, clean mixture of coolant and water.

Cap - After running for only a few minutes, the water in the radiator is extremely hot. CAUTION... Do not attempt to remove a radiator cap from a pressurized system. Pressures are usually in the 8 to 14 pounds per square inch (PSI) range but may be higher or lower based on the specific vehicle and the cooling system specifications. As the temperature of water, or a coolant and water mixture rises, the fluid expands creating pressure. After you have shut down an already hot engine, it will actually get hotter for a while as the water tries to absorb heat but since the fluid is no longer circulating, really does not dissipate it into the air. Let the system cool, or if the system is so equipped and you are knowledgeable of what you are doing, release the pressure prior to attempting to remove the cap. You will always have overflow if this is done.

Coolant - Most coolant, anti-freeze by common name, most of the time ethylene glycol or propylene glycol by formal name, is toxic. The degree of toxicity varies from brand to brand but all of it is dangerous to animals and humans. Use care when removing, adding or disposing of coolant from your vehicle's cooling system. Generally a 50-50 mixture of water and coolant is what is used in a cooling system. That mixture can vary with environmental conditions. However, as we so often suggest, read your owner's manual and follow that guideline. You can use our Coolant Percentage Calculator to determine the correct percentage or quantity. The efficiency of the coolant mixture is tested with a hydrometer.

Fans, belts and pulleys - Every engine has some quantity of fans, belts, pulleys or gearing chains to assist in the system cooling. Belts operate by friction on the pulleys and tension to keep them tight. They must be checked regularly and replaced as needed. When the engine is not running, they are rather harmless and easily visible. However, when the engine is running, they seem to disappear. CAUTION... Do not stick your hand anywhere around the engine UNLESS you know what you are doing. Severe injury or death can be the result. These components at a minimum, spin the water pump to circulate the fluid in the system. Depending on the position and type of fan(s), the purpose is to either pull or push air across the coils (containing heated fluid) of the radiator. As the vehicle moves through the air in normal motion, outside air is forced across those same coils by a ram effect, generally called air induction.

Hoses - There are most often 2 or 3 hoses in the cooling system, and 2 hoses in the heating system. One that comes from the radiator to the engine, the supply hose, with the thermostat usually at the point of engine connection; and one from the engine to the radiator, a return hose. The supply hose brings cooler water to the engine and the return hose takes heated water to the radiator to dissipate the heat. Sometimes there is a hose that bypasses the thermostat under certain circumstances; it is called the bypass hose. Often the bypass water routing is not a hose and alternatively, is inside the engine. The vehicle's heater is a small version of the cooling system and is actually part of the cooling system. There is a supply hose and a return hose to and from the heater core, much like the radiator. Hoses are under pressure and wear out from the pressure and heat exposure. They must be replaced as needed; visual inspection may detect them as swollen, cracked or leaking.

Thermostat - This is a heat sensitive valve that opens at a certain temperature and stays open until the temperature falls below that mark again. The thermostat allows the engine to keep the same fluid inside the cooling jackets of the engine until the temperature of that fluid reaches the opening temperature of the thermostat. That "valve change" temperature varies from the factory because of optional engine equipment, usually between 150 degrees and 180 degrees F (about 66 to 82 degrees C), although each vehicle can be different and thermostats can be changed for the environment, such as for the northland, mountains or desert. The ultimate objective of the thermostat is to keep the fluid flowing to be re-cycled and re-cooled when needed, so that the temperature of the engine remains in the anticipated optimum operating range.

Heater - While it does not sound like part of the cooling system, it actually is. When turned to on, it routes engine heated liquid through the core, a kind of radiator. A fan blows air across the coils of the core radiator with the purpose of blowing heated air into the cabin of the vehicle. As a secondary action, the heat in the water is dissipated somewhat. The heater has its own thermostat, inlet and return hoses, and an electrical fan.

Temperature sensor - This is often called the temperature sending unit. There may be more than one of these in order to monitor different sections of the cooling system. Most often, the sensor is connected to a light or gauge on the dashboard but they can be interfaced to the vehicle computer for information processing.