How to Check Your Coolant Level

Your vehicle has a number of fluids that are essential to check and top off as part of your routine auto maintenance program. Occasionally, you may also need to drain and refill a number of reservoirs in order to improve the lifespan of your engine and other essential components. One essential liquid to check is your coolant. Learn how to check the coolant level, when to refill your coolant, and how to spot some signs that it may be time to perform repairs on your radiator or other cooling system components.

Dangers of Low or Contaminated Coolant

The radiator uses a series of tubes and hoses to transport coolant, or antifreeze, and cool down your engine.

Without enough coolant, your engine may overheat. Engine cooling system problems could arise if you don’t have the right mixture of coolant, which is typically a 50/50 mix of antifreeze and water. Finally, a leak in the system could contaminate your coolant and prevent it from working properly.

Don’t wait for your engine to overheat, keep an eye out for any signs of a coolant issue. Just like your oil, you should be inspecting your coolant level to prevent any dangerous situation before it occurs. A few minutes of simple inspection and maintenance can prevent a wide range of issues with your engine.

Check Your Coolant Level and Color

Now that you know some of the warning signs to check for, it’s time to inspect your radiator and coolant reservoir. Make sure your vehicle is on level ground for accurate readings. You’ll also want to wait for it to completely cool down, as your radiator and coolant can become extremely hot.

Open your hood and locate your radiator and coolant reservoir. Some older vehicles don’t include a reservoir, but most modern vehicles have a small tank for filling and checking the coolant level. The reservoir should be clear plastic, so you can easily see the level of coolant and the maximum fill line.

Before you top off your coolant, inspect your current coolant for any unusual coloring or contaminants. Coolant comes in a range of colors, so it’s normal for it to be red, blue, yellow or green. However, if your coolant is colorless, rust-colored, has particles or is oily or sludgy, you’ll want to have it inspected by your local mechanic. These are all signs of contamination that may indicate more severe issues like a leak in your head gasket.

Other warning signs to look out for include cracked radiator hoses and an extremely low coolant level. These need to be repaired, or your new coolant may leak out.

If it’s difficult to identify the color of your coolant, you can also use a coolant tester to determine the condition of your coolant system. These testers can be found at your local AutoZone and are easy to use. They should include a guide that describes the different colors you may see and when to take action.

How to Fill Your Coolant

If your coolant looks great and is just a little low, top it off with premium engine coolant. While IAT formula coolant is the most popular option for most vehicles, be sure to use the same coolant that’s already in your vehicle.

Your owner’s manual will have more information about the correct type of coolant. Check to see if your brand of coolant needs to be mixed with water or comes pre-mixed. Adding pure coolant with no water can damage your radiator, while too much water mixture can prevent your coolant from working effectively at extreme temperatures.

Simply top off your coolant to the top of the maximum fill line and close the cap. Make sure that no debris enters your radiator or coolant reservoir. Be sure both the reservoir and radiator caps are secured and start your vehicle.

When to Drain and Replace Your Coolant

If you’ve noticed any serious signs of damage to your radiator, or any unusual coloring to your coolant, it may be time to drain and replace it. It’s a good idea to have a mechanic to perform these steps, as there could also be an issue with your head gasket or radiator.

First, locate the plug on the bottom of your radiator. Place a drain pan underneath and completely drain your old coolant. Inspect your drain pan for any signs of particles or contaminants, as these are most likely caused by a cracked radiator or compromised hose. You’ll need to perform additional repairs, or your new coolant will quickly become contaminated as well.

Refill your coolant, making sure to bleed any air out of the system, replace the plug and top off your coolant reservoir. Start your engine and drive carefully to test whether there’s any air caught in your system. Continue to inspect your coolant reservoir for any signs of a leak.

Never refill your coolant when your engine is hot. Always wait for it to cool down. If you open a radiator cap when the engine is still hot, you could be burnt by escaping steam or hot coolant. Even after opening the cap, pouring cold or room-temperature coolant into your hot system could crack a hot engine block.

Cracked, bulging, and leaking hoses need to be replaced before you refill your coolant. When you inspect the radiator, you should take a look at all the hoses. You’ll find them on the top and bottom of your radiator. Because of the extreme temperatures these hoses face, it’s normal for them to begin to wear out and crack over time. After you’ve drained your radiator, replace any damaged hose section for a sealed, secure system.

Shop for Quality Coolant and Repair Parts

Now that you know how to check antifreeze, it’s time to pick up quality antifreeze. For the best brands and competitive pricing, stop by your local AutoZone today. Discuss any coolant issues with knowledgeable staff to determine the best course of action and find a comprehensive solution to restore your vehicle’s performance.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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