Besides its function in cooling your engine, coolant also contains ingredients that inhibit rust in your engine. When these elements are depleted, you must replace the coolant. Check your Haynes manual or maintenance schedule to see how often you need to replace the coolant in your vehicle. It's a simple job you can do to keep your engine in top shape. There are several types of coolant available. Use the type recommended by your vehicle's manufacturer.
How can you tell if your coolant is ready to change? When your engine is cool, remove the radiator cap and test the coolant with a simple tool, known as a hydrometer, that checks the ratio of coolant-to-water. If there is discoloration of the coolant due to rust in the system, this also indicates its time for a change. Rust will also show up on the underside of the radiator cap.
Draining the coolant is easy. Locate the drain plug at the bottom of the radiator, usually at the far right or far left. With the engine cold, place a drain pan under the front of the vehicle and open the spigot on the drain plug. Once the coolant is flowing out, remove the radiator cap.
Before putting new coolant in, you should flush all of the old coolant from the radiator and engine. Disconnect the upper radiator hose and aim the hose towards the drain pan. Place a garden hose in the upper radiator and use water pressure to flush until the water comes out clear. This water must be disposed of with the old antifreeze.
Reconnect the radiator hose and close the spigot; now you're ready to add fresh coolant. The proper ratio of anti-freeze-to-water is 50/50, so pour half a gallon of coolant into a clean container and add half a gallon of water. Some coolants are packed already at this ratio.
Slowly pour the new coolant mix into the radiator. It takes some time for the coolant to circulate all through your engine. Stop when it comes up to the cap opening and give it time to settle. When it seems like no more can be added, replace the radiator cap and run the engine at idle for a few minutes, then let the engine cool and recheck the level.
Check the coolant level in the coolant recovery tank over the next few days (only when the engine is cool!). If the level keeps going down over time, check the radiator and hoses for leaks.
Back to Tips from the Pros