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Radiator Flush
By Tom Morr/
Printable version
Degree of DifficultyModerate
Estimated Time60 minutes
60 minutes
Cooling System Maintenance -

Drivers are often less educated about proper intervals for their vehicle's vital fluids. For the cooling system, antifreeze manufacturers recommend changing the coolant once a year, and some service manuals stipulate flushing and refilling the radiator every 24 months, regardless of mileage.
Cooling System Maintenance
Antifreeze Importance
Antifreeze manufacturers recommend changing the coolant once a year. Antifreeze serves two important functions: protecting the cooling system at temperature extremes and inhibiting rust and corrosion in the system. Many types of antifreeze also have additives that help lubricate the water pump and thermostat, so coolant has multiple advantages over plain water.
Draining & Flushing
Rust and sediment can accumulate in the cooling system. Flushing the radiator helps keep the cooling system clean. Begin by parking the car away from kids, pets and storm drains. Elevating the car on ramps can make the job easier.
With the ignition off, the engine cool, the car in Park and the emergency brake set, remove the radiator cap. Place a bucket or pan (minimum 2-gallon capacity) under the radiator drain plug and open it. Close the plug once the coolant flow ends. For more thorough draining, remove the plug(s) in the engine block (if so equipped) to release the coolant that remains in the engine.
If the old coolant appears rusty or contaminated, flush the system with a radiator-cleaning product to further remove sediment. With all drain plugs closed, fill the radiator with a flush/cleaner product and plain water. Then run the vehicle with the heater on high for as long as the flush product's instructions specify. Once the engine cools, drain the flushing solution, refill the radiator with plain water, and repeat the sequence following the flush's instructions.
Consult your vehicle's owner's manual and the antifreeze bottle for the proper coolant-to-water ratio, which can vary between 40% and 70% antifreeze based on the vehicle and climate. Fill the radiator appropriately, then fill the overflow reservoir to the appropriate level with a 50/50 mix. Clean up any spills immediately. Close the cap(s) and run the vehicle up to operating temperature with the heater on high to circulate the coolant throughout the system. Once the engine cools, check for leaks. After a few days of driving, double check the coolant mixture with a hydrometer or test strips (both of which are available inexpensively from the parts store) and adjust the concentration as necessary.
Various chemical additives are formulated to improve cooling-system performance while you drive. Rust inhibitors are designed to reduce oxidation and neutralize acids; many also include lubricants for the water pump and thermostat. Other chemicals improve the coolant's heat-dissipation properties and claim up to a 20°F reduction in operating temperature.
Flushing your car's cooling system isn't the most glamorous way to spend a Saturday morning. But just as your refrigerator's coils need periodic vacuuming for proper operation, keeping the car's cooling system clean is cheaper and easier than the consequences of ignoring it.
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