Coolant, also known as anti-freeze, is vital to your car engine’s health. The cooling system is responsible for transferring the heat created within the engine during combustion to the atmosphere. Coolant mixed with water in typically a 50/50 mix, circulates through the engine, absorbs heat, and flows to the radiator via the water pump and cooling passages to shed the heat. Low coolant levels can lead to the engine running hotter than designed and even an overheat condition which can damage the engine.

Part 1 of 1: Check and top off coolant

Materials Needed

  • Coolant

  • Distilled water

  • Funnel - not required but keeps from spilling coolant

  • Rags

  • Tip: Be certain to use the approved coolant for your vehicle and not the “approved for all vehicle” types. Sometimes the chemical differences between coolants can lead to a “gelling” of the coolant and clogging of smaller coolant passages within the cooling system. Also, buy straight coolant and not the 50/50 “pre-mixed” versions. You will be paying nearly the same price for 50% water!!

Step 1: Check the coolant level. Start with a cool/cold engine. Some vehicles do not have a cap on the radiator. Checking and topping the coolant is done strictly from the coolant reservoir. Others may have both a radiator and coolant reservoir cap. If your vehicle has both, remove them both.

Step 2: Mix coolant and water. Using an empty container, pour a 50/50 mixture of coolant and distilled water into it. Use this mixture to top off the system.

Step 3: Top off the radiator. If your vehicle has a cap on the radiator and no coolant is visible in the radiator, top it off until you see coolant at the bottom of the filler neck. Give it a moment to “burp” as there may be air trapped below. If it “burps” and the level drops a bit, fill it again to the bottom of the neck. If the level remains the same, replace the cap.

Step 4: Top off the coolant reservoir. The reservoir will be marked with MIN and MAX level lines. Fill the reservoir to the MAX line. Do not overfill it. The coolant mixture expands as it heats up and needs room to do so. Replace the cap.

  • Note: Even without a leak in the system, coolant levels can drop over time simply from boiling off. check the coolant level after a day or two or driving to verify the level is still correct.

If your low coolant light comes on or your vehicle is leaking coolant, have a mobile technician from YourMechanic inspect your cooling system at your home or office today.

This article originally appeared on YourMechanic.com as How to Top Off Car Coolant and was authored by Ronny Brown.


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