How to Change Coolant

Overview

In the old days (generally before 2000), changing your vehicle’s coolant was simple. That procedure is shown in Step 2, below. After 2000, cars got more complex and many DIYers got intimidated by the precise filling and “air-bleeding” procedures required to eliminate engine air pockets. But don’t worry, it’s easier than it looks. All it takes to get back in the game is a one-time $83 investment in an air-powered refilling tool. The details follow in Step 3.

Either way, you can change your coolant yourself in about an hour. But before you do anything, check your  owner’s manual for the recommended procedures and coolant for your car.

Draining and refilling coolant in older cars

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Photo 1: Open drain cock

Open the drain cock by unscrewing, twisting a quarter turn, or twisting and pulling. (The various styles are shown in the next photo.)

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Drain cocks

Drain cocks come in several different styles.

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Photo 2: Remove the hose

Push together the clamp spring with a slip-joint pliers and slip the clamp away from the neck. Pull the hose free and drain the remaining coolant. If access is difficult, a hose clamp pliers saves time and bruised knuckles.

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Hose clamp pliers

Hose clamp pliers are available at auto parts stores or online.

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Photo 3: Add coolant

Stir 1 gallon of full-strength (not premixed) coolant and 1 gallon of distilled water together in a clean bucket before adding the mix to the radiator.

If you're way past due for a coolant change and your cooling system is corroded, you should take your car in for a professional flush. The same is true if you've mixed different types of coolant in your radiator. But if you're on schedule for a coolant change and your coolant is free of brown, gunky corrosion (extract a little coolant with a baster to examine it), you can skip the flush procedure and perform a simple drain and refill operation yourself and save money. Here's how:

Start by buying the type of coolant listed in your owner's manual. If your manual calls for an “extended life” coolant that isn't available at the auto parts store, buy it from the dealer. Don't buy a “universal” coolant. Using the wrong coolant can cause premature component failure and void your warranty.

Raise and safely support the front end of your car on jack stands. Place a large drain pan under the radiator and remove the radiator cap. If your radiator doesn't have a cap, remove the pressure cap from the coolant tank. Then open the drain cock and drain the radiator.

Drain cocks come in several different styles—screw threads, quarter-turn twist, and quarter turn and pull. Plastic drain cocks become brittle with age and can break easily, especially if you try to unscrew a quarter-turn twist style. So, buy a replacement drain cock at the auto parts store before you begin the job (they only cost a few dollars; return it if you don't need it).

Then remove the lower radiator hose clamp and hose from the engine to drain the rest of the coolant. Use a slip-joint pliers to remove spring-style clamps. If you have trouble accessing or releasing the clamps with a pliers, buy a hose clamp pliers (see photo). Reconnect and clamp the radiator hose and reinstall the drain cock after draining.

Follow the coolant manufacturer's directions for diluting concentrated coolant. Mix the coolant and water thoroughly in a clean bucket. To prevent mineral deposits on internal engine and radiator surfaces, always use distilled water—never tap water. Leave the car raised while you refill the radiator to reduce the possibility of air pockets forming in the engine.

Slowly fill the radiator or coolant tank with fresh coolant until the coolant is 1 in. below the neck of the radiator or a few inches below the full mark on the coolant tank. Start the engine and let it run. After the engine warms, you'll see the coolant level quickly drop in the radiator/coolant tank. That means the thermostat has opened and it's time to add more coolant to bring the level to the top of the radiator, or to the “HOT” mark on the coolant tank. Check your owner's manual or service manual to see if your car requires a special air bleeding procedure. Check for leaks, shut off the engine, install the cap, lower the car and go for a spin.