How to Change the Coolant in a C5 Corvette

by Allen Moore
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C5 Corvettes came equipped from the factory with Dexcool engine coolant. Unlike standard antifreeze, which is green in color, Dexcool is orange. The main benefit of Dexcool is a longer life than the old green stuff, but regardless of GM’s extended maintenance interval, Dexcool should still be replaced regularly. In the late 1990s, GM vehicle owners began experiencing trouble with Dexcool-equipped vehicles; since then, GM has shortened the recommended service interval from 150,000 miles to 100,000 miles.

Step 1

Set the parking brake and place wheel chocks in the front and back of the rear tires to prevent the car from rolling.

Step 2

Put on your safety glasses and remove the coolant recovery bottle cap. Do not work on the cooling system when the engine is hot. It’s best to let the car sit for 12 hours before performing this procedure.

Step 3

Jack up the front end of the Corvette. Place jack stands under the front frame and carefully lower the car onto the jack stands.

Step 4

Place the drain pan under the lower radiator hose where it meets the radiator.

Step 5

Use the socket set to remove the radiator hose clamp where the lower radiator hose meets the radiator and slide the hose back, away from the radiator, being careful to immediately aim it down into the drain pan.

Step 6

Open the petcock on the bottom of the radiator and let it drain into the drop pan as well. You may need to use pliers to open the petcock, but use extreme care when doing so to prevent damage to the petcock or radiator.

Step 7

Close the petcock after all the Dexcool has drained, then slide the lower radiator hose back on and tighten the hose clamp back down. Do not over-tighten the clamp but tighten it just to the point where rubber begins to squeeze through the slots in the clamp band.

Step 8

Pour one gallon of Dexcool into the coolant recovery tank then add one gallon of distilled water. Continue to add a 50/50 mixture of Dexcool and distilled water until the fluid level in the tank is up to the cold fill line.

Step 9

Start the engine and let it warm up with the recovery tank cap off. The coolant level will go down a little as air escapes the system. Shut the car off after one minute and top off with coolant, again using a 50/50 mixture.

Step 10

Reinstall the coolant recovery tank cap and run the engine for 10 minutes. Check the coolant level: if it has gone down, let the engine cool and then top it off again.

Step 11

Inspect the petcock and lower radiator hose for leaks. Move the drain pan out of the way, then carefully jack the car back off the jack stands, remove the jack stands and lower the car back onto the ground. Recheck the coolant level again after the next day of driving.

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