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  • Cooling System Maintenance


Pooring coolant into an automotive radiator

Difficulty: Medium
Duration: 1 hour
How often: See your owner's manual

Why maintain your cooling system?

At least every two years, your vehicle's cooling system should be drained, flushed and refilled to replenish the antifreeze mixture and prevent the formation of rust and scale. Rust and scale can impair the cooling system's performance and cause damage to the engine.

These instructions will help you drain, flush and refill most popular vehicles. Although replacing coolant isn't difficult, be sure to READ these instructions completely before you begin working.

Make sure you get the correct coolant for your car. Check with your local NAPA Auto Parts store for the specific coolant your vehicle requires.



  • A container large enough to catch the old coolant as it drains out of the radiator.
  • A garden hose or large bucket for flushing the system.
  • A jug of new coolant.
  • A bottle of radiator flush


Proper maintenance and service procedures are vital to the safe, efficient operation of all motor vehicles, as well as to the safety of the person performing the work—you.

Whenever you are working on your vehicle, we recommend that you follow these important safety rules:

  • Do have a first-aid kit handy.
  • Do be careful when working around hot or sharp objects.
  • Do follow the manufacturer's instructions for all products.
  • Do use safety stands under the frame or drive-on ramps if you must raise your vehicle.
  • Don't run the engine without proper ventilation.
  • Don't smoke when working around the engine.


READ these instructions completely before you begin:

Draining the Old Coolant

Figure 1

  • BE SURE THE ENGINE IS COLD, press down on the radiator cap and slowly turn it counter-clockwise until it hisses. Wait until the hissing stops and remove the cap.
  • Make sure the heater's temperature control is on the hottest possible setting.
  • Place a large container under the radiator cap to catch the coolant as it drains.
  • Loosen the drain plug or petcock at the bottom of the radiator and allow the coolant to completely drain out.
  • If your radiator does not have a drain plug or petcock, disconnect the lower radiator hose and allow the coolant to drain. DO NOT get coolant in your eyes or on your skin.
  • If your vehicle is equipped with a coolant reservoir, disconnect all hoses connecting it to the radiator, remove the reservoir and flush it with clean water.
  • Properly dispose of or recycle the used antifreeze.

Flushing the System

Figure 2

  • Retighten the drain plug or petcock at the bottom of the radiator. If the lower radiator hose was disconnected to facilitate the draining of the cooling system, reconnect it.
  • Add water until the radiator is almost full.
  • Add one bottle (12 fl. oz.) of flushing product to the radiator.
  • Replace the radiator cap, start the engine and run at idle with the heater control on HOT for 10 to 20 minutes.
  • Stop the engine, open the drain plug or petcock, catch the fluid in a large container and dispose of it properly.WARNING: THE FLUID WILL BE HOT! TAKE SPECIAL CARE TO AVOID BURNING YOURSELF.
  • After the coolant has completely drained out of the radiator, place a garden hose in the radiator filler neck and flush out the system.
  • Flush the radiator until the water coming out of the drain hole, petcock or lower radiator hose opening is clear. If a garden hose is not available, use a clean bucket to pour fresh water into the radiator filler neck.
  • Inspect the rubber gasket and seal on the inside of the radiator cap for cracks or deterioration. If you replace the cap, make sure the new one has the same pressure rating as the old one. The pressure rating is stamped on the top of the cap.
  • Inspect all the radiator hoses for cracks or deterioration and replace them if necessary.

Refilling the Cooling System

  • Retighten the drain plug or petcock at the bottom of the radiator. If the lower radiator hose was disconnected to facilitate the flushing of the cooling system, reconnect it.
  • Reinstall the coolant reservoir, and reconnect all the hoses connecting it to the radiator as applicable.
  • Refer to your owner's manual to find the cooling system capacity. Add one-half of the capacity, using new antifreeze. Add enough water to finish filling the radiator. Also refill the coolant reservoir with new antifreeze to the "FULL COLD" level as indicated on the reservoir.
  • Run the engine at idle speed until it reaches normal operating temperature. With the engine idling, add enough water to refill the radiator. If you want, you can check the exact range of protection of the new antifreeze-water mixture with a simple float-type antifreeze tester.
  • Reinstall the radiator cap by pressing down and turning it clockwise until the arrows on the cap are aligned with the overflow hose coming out of the filler neck.
  • Reinstall the coolant reservoir cap.
  • Regularly check the coolant level and radiator hoses for leaks during the first few miles of driving. Tighten the hose clamps, and add additional coolant as needed.
  • For additional corrosion protection, add one bottle (12 fl. oz.) of radiator rust preventive product to the radiator (not the coolant reservoir).


  • Follow these instructions carefully. Read and be sure you understand them before you begin.
  • Gather all your tools and supplies before you begin.
  • Allow plenty of time to do the job so you don't have to hurry.
  • Remember that these are general instructions. For more detailed instructions pertaining to your specific vehicle, consult an appropriate repair manual.
  • Safety is important whenever you're working around machinery. Beware of hot objects, sharp instruments and hazardous materials.
  • Don't substitute tools unless you're sure it won't compromise either your safety or the performance of your vehicle.
  • If you have any questions about repair and maintenance, contact your local NAPA Auto Parts store.Find the nearest NAPA Auto Parts location.