How To Fill A 2003 Honda Civic Radiator

Learning how to fill a 2003 Honda Civic Radiator is a simple do-it-yourself auto maintenance task.  Filling your own radiator on your 2003 Honda Civic is quick and easy. Knowing how to replace the coolant in your Honda Civic radiator will save you time and money by cutting out an unnecessary/costly trip to the mechanic.

To fill a 2003 Honda Civic Radiator, you will need:

  • All Season Antifreeze/Coolant type 2
  • Commercial Radiator Pressure Tester (available at most auto parts stores)
  • Engine of the car MUST be Cool/Cold
  1. Open the hood of the 2003 Honda Civic.  Locate the radiator which is located in the front of the engine compartment next to the grill. The radiator cap is metal and can be found on top of the radiator just off center toward the passenger side. You will also need to know where the overflow/reserve tank for the radiator can be found. It is the plastic tank that is connected to the back of the radiator. It has a black plastic cap on top and two marked fill lines (MIN and MAX). 
  2. Make sure the engine is cool. Before beginning any maintenance on your radiator or before removing the radiator cap you MUST make sure the engine is cool. Removing the cap while the engine is hot can result in scalding and other injuries.
  3. Carefully pour All Season Antifreeze/Coolant into the fill neck until it reaches the top of the fill neck. Pour slowly allowing time for the coolant to completely fill the radiator chamber. Stop filling when the coolant becomes visible in the neck of the fill spout. Do not overfill. Avoid spilling coolant on the engine or the ground.
  4. Attach the radiator pressure tester to the radiator fill neck.  Follow the manufacture's instructions included with the pressure tester.
  5. Apply a pressure of 93-123 kPa (14-18 psi). Inspect the engine visually for coolant leaks. Check the gauge on the pressure tester  to make sure there is no drop in pressure.
  6. Remove the pressure tester and replace the radiator cap. Make sure to completely tighten the radiator cap. It should "lock" into the groove when it is completely tightened.
  7. Check the coolant level in the Honda Civic radiator reserve tank. Visually inspect the level to see if the coolant level is between the MIN and MAX lines. If the coolant is at or below the MIN line move on to step 2. If the coolant is between the lines you do NOT  need to add additional coolant.
  8. Remove the black plastic cap on the  coolant reserve tank. Carefully pour coolant into the tank until the level reaches the MAX line. Do not over-fill.
  9. Replace the black plastic cap on the 2003 Honda Accord radiator reserve tank. Visually inspect for leaks.
  10. Wipe up any spilled coolant.

 When filling the radiator of a 2003 Honda Civic always use All Season Antifreeze/Coolant type 2. It is recommended by the manufacturer.


  • Antifreeze/coolant is poisonous to humans and animals. it is sweet to the taste and many pets will lick at puddles or spills that may have occurred. Please be sure to clean up your area when you are finished and store any remaining coolant out of the reach of children and pets.
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