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How to Refill Engine Coolant

by Sophie Reynolds

Checking your vehicle’s engine coolant level and concentration should be part of your vehicle’s preventative maintenance routine. A low coolant level will cause engine overheating, which can damage your vehicle’s engine. According to the Society of Automotive Engineers (SAE), using an incorrect concentration of engine coolant or “antifreeze” may result in cavitation corrosion, water pump failure, scale formation, gelation, inefficient heat transfer, boil over, freezing and cracking engine blocks. Refilling or “topping-off” engine coolant in your vehicle is a task that you can easily do yourself.

Step 1

Place your hand on the hood of your vehicle to make sure the car engine is cool. If the hood of the vehicle is warm or steam is coming from under the hood, wait until the engine is cool before proceeding further.

Step 2

Locate the hood release under the dash of your vehicle, then pull. Open the hood. Locate the coolant reservoir, which is generally made of a white plastic. Look at the coolant reservoir to see how much fluid is inside of the coolant reservoir. The coolant level should be between the "LOW" and "FULL" marks on the coolant reservoir tank.

Step 3

Select a premixed coolant or mix your coolant with distilled water according to the instructions on the label of the coolant. Generally, the coolant to distilled water ratio is 50:50.

Step 4

Test the coolant concentration with a hydrometer or test strips for engine coolant. If using a premixed, ready to use engine coolant, skip this step.

Open the plastic cap on the coolant reservoir. Place a funnel into the reservoir. Pour the properly mixed coolant into the coolant reservoir until the fluid level reaches the "FULL" mark. Place the reservoir cap back on and shut the hood of your vehicle.


  • Before purchasing a coolant, check your owner's manual to find which coolants are compatible with your vehicle’s engine. You should also check your owner’s manual to verify that you are able to correctly identify and to distinguish between your car’s engine coolant reservoir and the windshield fluid reservoir. Adding the wrong fluid to a fluid reservoir may result in damage to your vehicle.
  • If you operate your vehicles in an area where winters are harsh, you might consider increasing the coolant to distilled water ratio to 60:40 improves freeze point protection. However, a ratio of more than 70:30 reduces your vehicle’s freeze point protection level.


  • To avoid serious injury, never open your vehicle’s radiator or coolant reservoir tank when the engine is hot.

Items you will need

  • Engine coolant
  • Funnel
  • Distilled water
  • Hydrometer or test strips

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