How often should I change my antifreeze?

For “ordinary” antifreeze, the vehicle manufacturers generally recommend coolant changes every two to three years or 30,000 miles. Others say it’s not a bad idea to change the coolant every year for maximum corrosion protection — especially in vehicles that have aluminum heads, blocks or radiators. But such recommendations may soon be obsolete. Several antifreeze suppliers have just recently introduced “long life” antifreeze formulations that claim to provide protection for four years or 50,000 miles.General Motors just introduced a new five year, 100,000 mile antifreeze in its 1996 cars and light trucks. The new coolant is called “Dex-Cool” and is dyed orange to distinguish it from ordinary antifreeze (which is green).CAUTION: These new long life coolants provide extended life only when used in a clean system mixed with water. If mixed with ordinary antifreeze and/or old coolant in a system, the corrosion protection is reduced to that of normal antifreeze (2 to 3 years and 30,000 miles).CORROSION INHIBITORSThe life of the antifreeze depends on it’s ability to inhibit corrosion. Silicates, phosphates and/or borates are used as corrosion inhibitors to keep the solution alkaline. As long as the antifreeze remains so, corrosion is held in check and there’s no need to change the coolant. But as the corrosion inhibiting chemicals are used up over time, electrolytic corrosion starts to eat away at the metal inside the engine and radiator. Aluminum is especially vulnerable to corrosion and can turn to Swiss cheese rather quickly when conditions are right. Solder bloom can also form in copper\brass radiators causing leaks and restrictions. So changing the coolant periodically as preventative maintenance is a good way to prevent costly repairs.The basic idea is to change the coolant before the corrosion inhibitors reach dangerously low levels. Following the OEM change recommendations is usually good enough to keep corrosion in check, but it may not always be the case. That’s why more frequent changes may be recommended to minimize the risk of corrosion in bimetal engines and aluminum radiators.CHECKING THE ANTIFREEZEOne way to find out if it’s time to change the antifreeze is to test it. Several suppliers make special antifreeze test strips that react to the pH (alkalinity) of the coolant and change color. If the test strip indicates a marginal or bad condition, the coolant should be changed.CHANGING THE COOLANTReverse flushing is the best way to change the coolant because draining alone can leave as much as 30 to 50% of the old coolant in the engine block. Reverse flushing also helps dislodge deposits and scale which can interfere with good heat transfer.The concentration of antifreeze in the coolant also needs to be checked prior to the onset of cold weather. A 50/50 mixture of antifreeze and water is recommended and will protect against freezing down to -34 degrees F and boilover protection to 263 degrees F.For maximum protection, up to a 70% mixture of antifreeze can be used for freezing protection to -84 degrees F.CAUTION: Do not use more than 70% antifreeze, and never run straight water in the cooling system because it offers no corrosion, freezing or boilover protection.

Flushing the System RADIATOR

The original additives in antifreeze fight rust and corrosion breakdown and are ineffective after 1 to 2 years. This is because of the continual exposure to the heat in the cooling system. After the additives break down, rust begins to form rapidly. Therefore, a rust-colored antifreeze is an indication that the cooling-system service is required.

The cooling system should be cleaned periodically to remove rust, scale, grease, oil, and any acids formed by exhaust-gas leakage into the coolant. Recommendations vary; for example, Chevrolet recommends that the cooling system be drained and flushed every 2 years.

Flushing (cleaning) of a cooling system should be done based on the manufacturer’s recommendations or when rust and other contaminants are found in the system. Flushing involves running water or a cleaning chemical through the cooling system to wash out contaminants. Rust is very harmful to the cooling system because it causes premature water pump wear and can collect and clog the radiator or heater core tubes. There are three methods of flushing-fast flushing, reverse flushing, and chemical flushing.

Fast flushing is a common method of cleaning a cooling system because the thermostat does not have to be removed from the engine. A water hose is connected to a heated hose fitting. The radiator cap is removed and the petcock is opened. When the water hose is ON and water flows through the system, loose rust and scale are removed.

Reverse flushing of a radiator requires a special flushing gun device that is connected to the radiator outlet tank by a piece of hose (fig. 6-14 ). Another hose is attached to the inlet tank, so the water and debris can be directed to the floor drains. Compressed air, under low pressure, is used to force water through the radiator core backwards. The air pressure is used intermittently to loosen scale and sediment. Excessive air pressure should be avoided to prevent damage to the radiator. Starting and stopping the water flow produces a fluctuation in pressure and tends to loosen all foreign matter clinging to the passages in the radiator core.

Reverse flushing can also be used on the engine block and head (fig. 6-15 ). First, remove the thermostat and disconnect the upper radiator hose. Then disconnect the lower radiator hose at the water pump. Insert the flushing equipment in the upper radiator hose.

Reverse flush the system by sending water and air through the water jackets and coolant passages. Following the flushing, replace the thermostat and hoses so the system can be refilled.

When reverse flushing equipment is not available, you can still reverse flush the system with a garden hose. This is often effective following the use of a chemical cleaner.

Chemical flushing is needed when a scale buildup in the system is causing engine overheating. Add the chemical cleaner to the coolant. Run the engine at fast idle for about 20 minutes. Wait for the engine to cool. Then drain out the coolant and cleaner solution. Using a garden hose, flush out the loosened rust and scale. Continue to flush until the water runs clear.

CAUTION

Always follow manufacturer’s instructions when using a cooling system cleaning agent. Wear protective gloves and goggles when handling cleaning agents. Chemicals may cause eye and skin burns.

How to Mix Car Coolant

On its own, coolant helps your car flush built-up heat out of its radiator to prevent your car from overheating. However, if you mix coolant with water in the proper ratio, you can also reap the benefits of the coolant's or antifreeze's anti-corrosive properties. You'll need to consult your car's owner's manual to learn the proper specifications for use of antifreeze or coolant, but there are several general principles to keep in mind when you mix car coolant with water.

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Instruction

1. • 1
     Consult your car's manual. There will be a section dedicated to coolant or antifreeze-usage specifications. If you cannot find this information, contact your car's manufacturer to learn the specs you need to know before proceeding.
   • 2
     Stick to brand-name coolants, such as Prestone and ThermalTake.
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   • 3
     Mix your antifreeze at a one-to-one ratio with water. For temperate climates, this will provide the protection you need in winter weather and effectively work to keep your engine from overheating. In addition, a 50/50 coolant-to-water ratio fights rust, boiling and engine corrosion.
   • 4
     Mix an ethylene-glycol coolant with water in a 70:30 ratio (in other words, 70-percent coolant to 30-percent water). This is recommended if you live in an environment that experiences harsh winter weather. It is also the highest coolant-to-water ratio that most experts recommend for use in car engines.
   • 5
     Combine factory antifreeze or coolant products, such as DEX-COOL, with water at a ratio not exceeding 60:40 (60-percent antifreeze or coolant to 40-percent water). Mixing a long-life factory antifreeze product like DEX-COOL with water does not take away from its efficacy and may actually help it last longer. However, combining DEX-COOL with other coolant or antifreeze products can diminish its potency.
   • 6
     Make absolutely certain that both your car's engine and coolant system are completely cool before you begin to work with them. When you have drained your car's coolant system and achieved the proper mixture of antifreeze or coolant and water, refill your car's coolant system with the appropriate solution and hit the road.
   • 7
     Learn more about coolant on the Road & Travel Magazine website (see Resources below).

Tips & Warnings

• While a long-life factory antifreeze product will have a life of 5 years or 150,000 miles, you will shorten this lifespan if you mix it with other coolant products. Many people simply mix ethylene-glycol coolant with their existing antifreeze because they don't realize they're actually compromising the overall efficacy of their coolant.
• It is best not to mix different types of coolant or antifreeze with one another, unless it is unavoidable. A much better solution is to drain your car's coolant system and refill it with a single coolant-and-water mixture.
• Use softened water whenever possible. Hard water can affect the chemical makeup of some coolant products.

| eHow.com