How to Flush Your Radiator on Your Own and Save Money

Your radiator is an essential part of your vehicle – it keeps the engine from overheating and also protects against freezing temperatures. However, just like every other vehicle system, your radiator needs to be properly maintained. While you won’t have to drain and fill your antifreeze with the same regularity you’ll need to change your engine oil, it does need to be flushed and filled periodically. There’s good news too; you can do this on your own very easily, and save both time and money.

When to Flush

As mentioned, flushing your radiator isn’t something you’ll need to do frequently, but it should be done on a regular basis. Most cars should have their radiator flushed and filled every five years or so. Older models should have more frequent flushes, particularly if there are signs of cooling system deterioration.

Watch What You’re Doing

Flushing and filling your radiator is good not only for keeping your cooling system in good shape, but for making sure it’s healthy as well. While the coolant drains out, keep an eye on it for signs of damage (white flakes, gunk and debris in large amounts can all be signs of impending doom).

What to Do

If you’re prepared to flush and fill your radiator, there are only a few simple steps you need to take. First, make sure you have the essentials:

  • Replacement coolant
  • A catch pan for the old coolant
  • A source of clean water
  • A funnel
  • Rubber gloves

Step 1:

Wait until the engine has cooled enough that the antifreeze will not burn you and the system is no longer pressurized. Open the radiator cap. Place the catch pan under the car.

Step 2:

Locate the drain cock under your radiator. Turning this opens the valve at the bottom of the radiator and allows the old coolant to drain out. Do not attempt this until the engine has cooled down. Make sure the catch pan is directly below the drain.

Step 3:

Open the drain cock and allow the coolant to drain out. Allow the car to sit for several minutes (it can take some time for the coolant to drain out).

Step 4:

Close the drain cock and fill the radiator with clean tap water. Fill the radiator until the water comes to the top of the opening in the radiator’s fill neck.

Step 5:

Crank your car (with the radiator cap off). Allow the car to run and warm up. Once the cooling fan cycles on, you know the thermostat has opened and water has flushed through the system. Turn the car off.

Step 6:

Drain the water from the radiator by opening the drain cock and draining the water/antifreeze mix into the catch pan.

Step 7:

This step can be omitted unless you purchased a chemical flush kit. Note that flush kits are really only recommended for high mileage engines with serious scaling in the radiator. If you have a kit, add the fluid and water now and repeat the above steps, following the directions on the can. Drain the mixture when done.

Step 8:

With the drain open (and the car off), add water to the radiator. It should flow through the system and out the drain, carrying with it any remaining antifreeze and debris. When the water turns clear, stop filling it and allow it all to drain out.

Step 9:

Close the drain and refill the radiator with clean antifreeze. When the radiator is full, start the car and allow the cooling fan to cycle on (signifying that the thermostat has opened and the system is cycling). Top off the coolant in the radiator and reservoir with your fresh antifreeze until it reaches the full mark. Check it with a hygrometer to make sure you have enough protection from freezing.

Don Elfrink is the owner and operator of AutoMatStore, an auto flooring company based out Columbia, Missouri. Before AutoMatStore, Elfrink was the operator of an automotive production site. AutoMatStore floor mats consist of customized logo, carpet, molded and all weather mats.

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