A classic car's radiator.

Getting Ready for Winter: Radiator Flush

Cooler weather is an important signal to classic-car owners, reminding them to get their autos ready for winter. Unless you store your vehicle in a climate-controlled building, it will be subject to temperature variations that can take a toll on the radiator or the engine, possibly leading to repairs. Therefore, an annual radiator flush is one of the necessary winter storage preparation tasks that safeguard your classic car.

Radiator Flush: Once Annually

While some people replace their antifreeze annually and flush the system every other year, a yearly flush makes sense. This becomes especially important when you consider the alternatives: replacing a radiator tank, core or an engine block.

Here’s how to get the job done:

1. Assemble your primary supplies. One of the two main supplies you’ll need is a radiator flush and cleaner. This product removes rust, corrosion, scale and concentrated elements from the cooling system. You’ll also need new coolant — choose either a 100-percent solution or a 50/50 pre-diluted formula. If you go with the first choice, you’ll need to add distilled water to adjust the protection ratio. A drain pan, funnel, safety glasses and gloves are also necessary.

This photo is from my personal collection.2. Consider acquiring the following supplies. Beyond the flush and coolant, you might change out the radiator cap, thermostat, as well as the upper and lower hoses. The first two items can fail without notice, so replacing them may prevent a problem. As for the hoses, they’re prone to eventual cracking, blistering and leaking, and should be swapped out on a regular basis.

3. Start your work. You should attempt a radiator flush only when the car is cool. Once it is, release the pressure cap on top of the radiator tank. Air will enter it and push coolant out when you release the drain plug, which is typically found at the bottom of the radiator. Slowly release the plug and drain the coolant. You’ll collect about two gallons of old fluid in the process.

4. Flush the radiator. With the drain plug firmly in place, begin the flushing process. Pour the flush into the radiator through a funnel and add distilled water per the instructions. Reattach the cap and snap it in place. Turn on the car and set the heat to high, which will send the flush throughout the entire system. After a few minutes, turn off the car and allow it to cool down completely. Drain the flush into a pan, then dispose of the old fluid. Secure the plug and replace the old hoses, as necessary. Swap out the thermostat and radiator cap.

5. Put in new fluid. Pour a 50/50 mix of coolant and distilled water into the radiator. Once complete, start the car with the cap off to allow air to draw the antifreeze into the system. Add the fluid, then turn off the car to allow it to cool down. Then check coolant levels and add more as required. Secure the cap, look for leaks and finish the rest of your winter storage tasks.

Winter Storage Tips

Complete your winter storage checklist while weather conditions are still favorable. Keeping tabs on your classic car throughout the season to ensure no leaks have developed or that a critter hasn’t taken up residence in it will also help you get the vehicle back on the road quicker in the spring.

Check out all the chemical products available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on winter car maintenance, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photos courtesy of Matthew C. Keegan.

about author

Matthew C. Keegan

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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