Radiator Flush

Radiator Flush

Cooling-system maintenance

Most motorists know it's recommended that our vehicle's oil should be changed about every 3,000 miles. Drivers are less educated, however, about proper intervals for their vehicle's other 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.

Antifreeze manufacturers recommend changing the coolant once a year.

Antifreeze Importance

Antifreeze serves two important functions: protecting the cooling system at temperature extremes and inhibiting rust and corrosion in the system. Many antifreezes also have additives that help lubricate the water pump and thermostat, so coolant has multiple advantages over plain water.

Glycol Styles

Antifreeze's active ingredient is glycol. "Standard" coolants contain ethylene glycol (EG), which is toxic to people, pets, wildlife and groundwater. In recent years, less-toxic antifreezes containing propylene glycol have become available. These products advertise comparable cooling qualities to EG antifreezes but with less environmental impact. Either way, always clean up any coolant spills/radiator boil-overs promptly.

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, engine cool, car in Park and 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 proper coolant-to-water ratio, which can vary between 40% and 70% antifreeze based on 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-degree 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.


Gunk, www.gunk.com, Justice Brothers, www.justicebrothers.com, Peak, peakantifreeze.com, Prestone, www.prestone.com, Redline, www.redlineoil.com, Sierra, www.sierraantifreeze.com, Wynn's, www.wynns.be, Zerex/Valvoline, www.valvoline.com

radiator care, flushing your radiator, radiator flush
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