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RADIATOR 101 - Maintaining Your Auto-Radiator

If at any time your cars temperature climbs beyond the normal range, the engine is running in the danger zone. Conversely, if the car will not warm up sufficiently, the thermostat is not functioning properly, the culprit; most likely the thermostat is not closing.

The radiator is one of the most important operating parts of your vehicle. It’s task is keeping your automobile's engine at a safe operating temperature, a bad radiator could mean serious trouble for you if you do not seek professional mechanical attention immediately.

Unfortunately, radiator problems can often develop without the owner even knowing it, small particles of dirt and rust clogging up the essential elements, preventing your car radiator from being able to cool your engine properly. If this happens, your vehicle will over heat, potentially leaving you stranded. The best way to avoid such problems, which will inevitably happen with all automotive radiators as they age, is with regular routine maintenance and service. Being vigilant will help you catch minor car radiator problems before they become major ones.

Your vehicle engine runs on heat. Chemical energy in the fuel is transformed into thermal energy when the fuel burns, which produces mechanical energy to push the pistons, spin the crankshaft and drive the vehicle down the road.

As efficient as today's engines are, they still waste a lot of the heat energy they produce. The average gasoline engine is only about 25 percent (depending on your vehicle) efficient. That means over two-thirds of the heat produced by each gallon of fuel either goes out the tailpipe or is soaked up by the engine itself. Diesels provide for a little more bang for the buck, as they provide about 35 percent, but even that leaves a lot of waste heat that must be managed and carried away by the cooling system.

Interestingly, the hotter an engine runs the more efficient it becomes. But there's a limit because aluminum pistons and heads (that is what your engine is mostly composed of) can only get so hot before they start to soften and melt. The same goes for cast iron.

Most engines today are designed to operate within a "normal" temperature range of about 195 to 220 degrees F. A relatively constant operating temperature is absolutely essential for proper emissions control, good fuel economy and performance.

A 50/50 mixture of water and ethylene glycol antifreeze in the cooling system will boil at 225 degrees if the cap is open. But as long as the system is sealed and holds pressure, a radiator cap rated at 15 psi will increase the boiling temperature of a 50/50 coolant blend up to 265 degrees. If the concentration of antifreeze to water is raised to 70/30 (the maximum), the boiling temperature under 15 psi (look on top of your radiator cap) of pressure goes up to 276 degrees.

Signs and consequences if the engine overheats the first thing that will happen is a gasoline engine will start to detonate. The engine will ping and start to lose power under load as the combination of heat and pressure exceed the octane rating of the fuel. If the detonation problem persists, the hammer-like blows may damage the rings, pistons or rod bearings.

Overheating can also cause pre-ignition. Hot spots develop inside the combustion chamber that become a source of ignition for the fuel. The erratic combustion can cause detonation as well as engine run-on in older vehicles with carburetors. Hot spots can also be very damaging and burn holes right through the top of pistons.

Another consequence of overheating may be a blown head gasket. Heat makes aluminum swell almost three times faster than cast iron.

The resulting stress can distort the head and make it swell in areas that are hottest, like those between exhaust valves in adjoining cylinders, and areas that have restricted coolant flow like the narrow area that separates the cylinders. The typical aluminum head swells most in the middle, which can crush the head gasket if the head gets hot enough. This will cause a loss of torque in the gasket allowing coolant and combustion leaks to occur when the head cools.

Overheating can be caused by anything that decreases the cooling system's ability to absorb, transport and dissipate heat, such as a low coolant level, loss of coolant (through internal or external leaks), poor heat conductivity inside the engine because of accumulated deposits in the water jackets, a defective thermostat that doesn't open, poor airflow through the radiator, a slipping fan clutch, an inoperative electric cooling fan, a collapsed lower radiator hose, an eroded or loose water pump impeller or even a defective radiator cap.

Heat always flows from an area of higher temperature to an area of lesser temperature, never the other way around. The only way to cool hot metal, therefore, is to keep it in constant contact with a cooler liquid. And the only way to do that is to keep the coolant in constant circulation. As soon as the circulation stops, either because of a problem with the water pump, thermostat or loss of coolant, temperatures begin to rise and the engine starts to overheat.

The coolant also has to get rid of the heat it soaks up while passing through the block and head(s). So the radiator must be capable of doing its job, which requires the help of an efficient cooling fan at slow speeds.

Finally, the thermostat must be doing its job to keep the engine's average temperature within the normal range. If the thermostat fails to open, it will effectively block the flow of coolant and the engine will overheat.

Maintaining your Auto Radiator:

  • Thermostat - Severe overheating can often damage a good thermostat. If the engine has overheated because of another problem, the thermostat should be tested or replaced before the engine is returned to service. The hose should not feel uncomfortably hot until the engine has warmed-up and the thermostat opens. If the hose does not get hot, it means the thermostat is not opening. If the thermostat needs to be replaced, install one with the same temperature rating as the original. On newer vehicles with computerized engine controls, the wrong thermostat can prevent the computer system from going into closed loop resulting in major performance and emission problems if the engine fails to reach its normal operating temperature.

  • Cooling system leaks - Loss of coolant because of a leak is probably the most common cause of overheating. Possible leak points include hoses, the radiator, heater core, water pump, thermostat housing, head gasket, freeze plugs, automatic transmission oil cooler, cylinder head(s) and block. the radiator cap could be weak (or one with too low a pressure rating for the application) will lower the coolant's boiling point and can allow coolant to escape from the radiator.

  • Fan - With mechanical fans, most overheating problems are caused by a faulty fan clutch - though a missing fan shroud (covers the fan blade) can reduce the fan's cooling effectiveness by as much as 50 percent (depending on the fan's distance from the radiator), which may be enough to cause the engine to overheat in hot weather or when working hard. Defective fan clutches are a common and often overlooked cause of overheating. the life of a fan clutch is about the same as a water pump.

  • Water pump - Any wobble in the pump shaft or seepage would call for replacement. In some instances, a pump can cause an engine to overheat if the impeller vanes are badly eroded due to corrosion or if the impeller has come loose from the shaft. (Note: Some engines with serpentine drive belts require a special water pump that turns in the opposite direction of those used on the same engine with ordinary V-belts)

  • Belts & hoses - Check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough and/or the fan from turning fast for proper cooling. The condition of the hoses should also be checked. Recommend new hoses if the old ones are over 5 years old. Sometimes a lower radiator hose will collapse under vacuum at high speed and restrict the flow of coolant from the radiator into the engine. This can happen if the reinforcing spring inside the hose is missing or damaged.

  • Radiator - The most common problems radiators is clogging and leaks. Dirt, bugs and debris can block air flow through the core and reduce the radiator's ability to dissipate heat.

Coolant should be changed at least every two years or 30,000 miles or it will lose its effectiveness, and the mixture of antifreeze and water should always be 50/50.

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