How to Change Antifreeze in a Duramax

by Robert Tomashek

Seven gallons might sound like a lot of coolant for your 2013 Duramax, but then it's a big, heavy-duty engine. When your Duramax is due for its first cooling system service at 150,000 miles it will take 3.5 gallons of coolant and 3.5 gallons of distilled water in a 50-50 mixture.

Step 1

Turn the steering wheel turned all the way to the right. Shut the engine down and let it cool completely. Open the hood and remove the cooling system pressure cap. Remove the plastic pop rivets that hold the front section of the passenger-side wheel-well liner by gently prying them loose with the screwdriver and then pulling them out with the pliers. Lower the front of the liner to gain access to the lower radiator hose.

Step 2

Place the coolant catch pan under the lower radiator hose. Remove the metal clip that holds the lower radiator hose to the radiator by lifting it from its groove with the screwdriver. Pull the hose from the radiator and allow the coolant to drain. Reinstall the lower radiator hose and place the clip back into the groove until it sits flush. Make sure that the hose is tight by gently pulling on it. Move the wheel liner back into place and push the rivets back into place by hand.

Step 3

Move the coolant catch pan under the engine block. Locate the block drain plugs -- they are on both sides of the engine towards the front and have a spot to fit a 3/8-inch ratchet. Remove the drain plugs and allow the coolant to drain. Coat the drain plug threads with the silicone sealant. Install the drain plugs into the engine and torque them to 44 foot-pounds with your torque wrench.

Step 4

Fill the cooling system with a 50-50 mix of Dex-cool coolant and distilled water. Start the engine and keep the coolant level topped off. Hold the engine at 2,500 rpm for five minutes, and then allow it to idle for five minutes, topping off as needed. Repeat the cycle until the coolant level no longer drops. Install the cooling system pressure cap. Check the coolant level again after driving a few miles.

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