How to Add Water to My Radiator?

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How to Add Water to My Radiator?
Radiator cap with hose that leads to the reservoir. (Morguefile)

Adding water to the radiator can be a little intimidating, and steam burns and overheating await those who do not do a proper job. The good news is that a doing a proper job is not difficult or time consuming, and you get all of the rewards that come from working on your own car.

Skill level:

Things you need

  • Cardboard
  • Antifreeze tester bulb
  • Rag
  • Funnel
  • 2 gallons of distilled water
  • Antifreeze/coolant liquid (not premixed)

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  1. 1

    Gather your tools. Place a piece of cardboard under your car--antifreeze is toxic to animals and people, and should never be left on the ground. Wait for the car to cool completely before opening the radiator (see Warnings below).

  2. 2

    Check the coolant level. The opaque overflow reservoir (it resembles a plastic milk jug) has an indicator line that indicates the maximum level of coolant with something like "COLD FILL LINE" and an arrow that points to a line. This gives you and estimation of the relative fluid level when the motor is running. Look into the radiator to see the actual level of fluid as it is added.

  3. 3

    Locate the radiator cap. It is usually a large metallic cap on the radiator with a warning that it should never be opened hot. Check your car's manual to make sure you have the right location.

  4. 4

    Wrap a rag on the cap and rotate it counterclockwise. You may feel a little resistance as you twist it. When you can go no further, press down on the cap and continue twisting in the same direction. The cap should lift off easily.

  5. 5

    Look inside the radiator. You should see some of the green fluid. Squeeze the bulb of the antifreeze tester. Insert the end of the antifreeze tester into the radiator cap and allow the bulb to suck up antifreeze to the fill line of the plastic gauge.

  6. 6

    Look at the indicator arrow and where it points on the side of the scale. Make sure that the side of the gauge that indicates minimum temperature corresponds with the coldest temperature in your area; the other side should correspond to the hottest temperature in your area.

  7. 7

    Add more antifreeze if the temperature indicated on the scale is too high. Add distilled water if the temperature is too low. If the temperature is right but the fluid level is low, add coolant (mixed according to instructions on the container).

  8. 8

    Retest the mixture as needed after the engine runs and cools again (to mix the fluid). Some coolants come pre-mixed and need no water. Other coolants usually require a mixture of coolant and distilled water (equal parts of each).

  9. 9

    Put a clean funnel into the radiator. Pour the liquid very slowly so that the radiator does not overflow. Put the cap back on by pressing down and rotating it clockwise.

Tips and warnings

  • The terms "antifreeze" and "coolant" are used interchangeably in this article.
  • If you are having trouble getting the liquid to flow into the radiator, tip the mouth of the bottle towards the antifreeze tester's inserted tube.
  • Visually inspect your coolant for discolouration and have it flushed it the coolant is discoloured or dirty.
  • Wear gloves and goggles when attempting this procedure.
  • The radiator should be opened only when the engine is completely cool. Hot coolant and steam can cause serious burns.
  • If you get antifreeze on your skin, clothes or anything else, immediately wash it off with large amounts of water.
  • Dispose of any antifreeze or related products appropriately to prevent poisoning.
  • If you are exposed to antifreeze, call 911 and ask for an ambulance and to be transferred to Poison Control for more immediate measures.

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