How to Top Off Car Coolant

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.

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16 years of experience
157 reviews
16 years of experience
Mercury Grand Marquis V8-4.6L - Cooling System Flush - Tampa, Florida
it was very pleasant .he explained things to me where I could understand knew what he was doing got done in a reasonable amount of time
Mini Cooper - Cooling System Flush - Saint Petersburg, Florida
Excellent work. Very skilled. Took the time to explain the issue and the solution to me. Very satisfied. Thanks.


5 years of experience
91 reviews
5 years of experience
Chevrolet Silverado 2500 HD V8-6.0L - Cooling System Flush - Stockbridge, Georgia
Jared arrived early and repair was completed before the expected time. He was very pleasant, and courteous. He showed me what he was going to do, explained things to me in terms I understood. I was so pleased in how professional Jared. I would definitely recommended his as Your Mechanic!!
Mazda 6 - Cooling System Flush - McDonough, Georgia
Jared is professional and a freindly mechanic that works with passion. He explains things well and do whatever it takes to solve the issue. Explained everything in detail and did a fantastic job. All the required services were completed within the time frame. Jared arrived on time. Thank you Jared.


18 years of experience
146 reviews
18 years of experience
Mercedes-Benz GL450 V8-4.7L Turbo - Cooling System Flush - Roswell, Georgia
Caz was great, went above and beyond to locate hose needed for repair when local dealers were out or backordered because of supply chain issues. Traveled a few counties away to find part and get me back on the road. Knowledgable and explained process as well as recommended services car needed upon inspection.
Toyota Highlander - Cooling System Flush - Woodstock, Georgia
Caz is extremely knowledgeable and very personable. Explained everything to my level of understanding. I didn’t feel like I was being up charged for future work that needs to take place to keep my “mommy mobile” on the road. I truly enjoyed having him work on my vehicle and honestly, I will request him every time going forward. Fabulous mechanic.


22 years of experience
391 reviews
22 years of experience
Chevrolet Cruze L4-1.4L Turbo - Cooling System Flush - Rancho Cucamonga, California
Michael is through, respectful, professional and hard working. He knows his way around under the hood
Lexus RX400h - Cooling System Flush - Upland, California
He arrived in time and completed the job very professionally. He took time to explain other possible issues with the vehicle which should be done in future..

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