How to Check and Replace Your Vehicle’s Antifreeze

It’s important to ensure that your vehicle has the proper amount of coolant/antifreeze all year otherwise you run the risk of damaging your engine and cooling system. You need to check and replace your vehicle’s coolant regularly and these are the steps on how to do it.

Use an Antifreeze Tester

You can get an antifreeze/coolant tester from any automotive parts store. Simply follow the directions on the tester and fill it with some of the coolant from your radiator. The tester will indicate how much protection the coolant is providing, just refer to the directions on how to read it. If the antifreeze is breaking down, the tester will indicate it. A low protection reading means it is time to replace your coolant.

While you have some coolant in the tester, you need to check its appearance. If it is cloudy, rusty, or has any solid objects floating in it, then it is a sign that the anti-corrosion chemicals in the antifreeze have broken down and needs to be replaced. Be aware that some antifreeze is red in color, so don’t assume it is rusty just if it is red. There will be particles floating around if anything in the coolant system has begun to rust.

Check the Antifreeze Level

Most modern cars are equipped with a coolant reservoir tank which has a fill line on it. Check your owner’s manual to determine where the coolant tank is located. You should check your coolant level when the vehicle is cool. The coolant should be at or just above the minimum or fill line. If it is below this line, you should add a 50/50 mix of antifreeze and distilled water until your just above the line.

Older cars may not have a reservoir. Instead you will have to remove the radiator cap to see the fluid level. Make sure your engine is cool before you do this. The coolant system is under pressure when hot, and removing the radiator cap at this time will cause significant injury to you. If you have recently driven the vehicle, wait a few hours to give the vehicle plenty of time to cool down before opening the radiator cap. The antifreeze/coolant should be near the top of the radiator neck. If there is a “Full” or “Fill” line on the neck, then make sure the coolant level reaches that point. Consult your owner’s manual if you’re unsure of how much coolant should be in the radiator.

Use a 50/50 Mix of Antifreeze and Distilled Water

You should only use a 50/50 mix of distilled water and antifreeze to refill your coolant. Many automotive stores sell both pre-mixed antifreeze and 100% antifreeze containers. Make sure you know which one you’re getting because putting 100% antifreeze into your coolant system will damage your vehicle. Always mix the antifreeze and water before adding it to your radiator.

Be careful to use the same type of antifreeze that is recommended by your car’s manufacturer. There are a wide variety of antifreeze on the market today (see our article on mixing different antifreeze for more details). Adding the wrong kind of antifreeze can cause damage to your engine and cooling system. Consult your owner’s manual to determine the correct type of antifreeze to use.

What about a 70/30 Antifreeze/Water Mix?

For vehicles operating in extreme cold, a mix of 60/40 or 70/30 antifreeze to distilled water can be used to provide additional protection from cold. Never exceed a 70/30 mix or you will reduce your coolant’s ability to resist freezing. This may sound counter-intuitive but it is true. For most vehicles and conditions, a 50/50 mix is all you need. When in doubt, go with what your owner’s manual recommends.

Do I Need to Change my Antifreeze Regularly?

Yes, your antifreeze needs to be changed out on a regular basis. This is because most engines these days require corrosion inhibitors in the antifreeze to prevent damage to the engine. These inhibitors break down over time leaving your engine vulnerable to corrosion damage. Your vehicle owner’s manual will tell you at what intervals you should change the antifreeze. Most manufacturers recommend that you change your antifreeze anywhere from every 24,000 – 36,000 miles or every 24 to 36 months.

How to Flush Your Cooling System and Change Antifreeze

Changing your antifreeze is a simple process of draining the existing coolant, flushing the system with water, and then refilling it with a 50/50 mix of antifreeze and distilled water. While the process is fairly simple, you do have to capture all the liquid drained from the system for proper disposal. Antifreeze is highly toxic and it has a sweet taste. Animals and children who find it are likely to drink it, and it doesn’t require much for it to be fatal. For this reason you need to be prepared with multiple containers to catch all the antifreeze/water used to flush the system that you can then seal and take to an automotive store that will dispose of it for you. Here are the steps to change your antifreeze:

1. Make sure your vehicle has cooled sufficiently. Never change the antifreeze while the vehicle is hot!
2. Locate the drain valve for your coolant system (refer to your owner’s manual).
3. Place a large bucket underneath the drain valve and (optionally) attach a hose to the drain outlet and route it into the bucket (this can help prevent spills). The bucket should be able to hold at least two gallons.
4. Open the drain valve to allow the the coolant to drain. Everything should drain into the bucket.
5. Check the radiator hoses to ensure they are in good shape. If they look dried out or are starting to crack, you need to replace them.
6. Once the coolant is drained, close the drain valve and fill the system with water (preferably distilled water). Turn the engine on for about 10 minutes with the car’s heater turned on high. Watch the engine temperature gauge during this time to ensure it doesn’t start to overheat.
7. Turn your vehicle off and let it cool down. Once the radiator is cool to the touch, you can proceed.
8. Drain the coolant system again just like before. You must collect all the liquid that comes out as it will have traces of antifreeze in it and will be toxic.
9. Make sure the drain valve is closed, and refill the system with 50/50 antifreeze and water mix.
10. Bleed any air out of the coolant system by running your engine for a few minutes. Again, watch the temperature gauge to ensure your vehicle doesn’t overheat. It may help the air to escape by raising the front end of the vehicle.
11. Let your vehicle cool down and then check the coolant level. If it is below the “Fill” line, top it off with some more 50/50 antifreeze mix.
12. Gather all the drained coolant and water as well as any contaminated rags for disposal. They need to be in closed containers and clearly marked as toxic. Keep them out of reach of pets and children, and take it to an automotive shop or store as soon as possible.
13. Continue to check your coolant level for a few days to ensure you have no leaks. Top it off if the level seems low as there may still be some air bleeding out.

Changing your coolant regularly will help to extend the life of your engine as well as your radiator. If the coolant looks cloudy or has debris floating in it, you may have significant internal damage to your engine or radiator. It would be best to have an automotive shop take a look at it before the problem becomes too great.