How to Flush a Radiator

Flushing a radiator is a relatively simply job for a weekender mechanic with a basic tool set and a drain pan. We will talk you through a procedure after we discuss the importance and frequency of performing a radiator flush.

Just flushing your radiator will probably help solve some of the problem you’re having, but in reality it is probably a full cooling system flush that will serve you and your vehicle better. The radiator is the most accessible and visible part of your cooling system, so it is often the only part that we think to keep clean and well maintained. Once the coolant in your vehicle exits the radiator, it travels through your water pump and into engine block and heater core before it returns to the radiator. The water pump, engine block and heater also build up sediment, deposits and sludge so they need to be properly flushed as often as your radiator. Luckily it is easy to flush the whole system at once.

Newer cars do not require coolant flushes as much as your grandfather’s 2 door Plymouth coupe did. Old style brass or copper radiators combined with older water pump and coolant technologies lead to a lot of corrosion products and sludge build up in automobile cooling systems requiring very regular system flushes. New vehicles with aluminum radiators and cylinder heads, along with better water pump bearing and seals, combined with new high quality corrosion inhibiting coolants have helped keep modern automotive cooling systems much cleaner. You should check your vehicle owner’s manual to see how often your engine coolant should be replaced and perform a cooling system flush every time new coolant is added. For most new cars and trucks the system should be flushed at least every 100,000 miles. If you do not know when the last time your system was flushed, it would be better to be safe than broken down, so perform a cooling system flush on your vehicle soon.

Cooling System Flush Procedure:

1.) Ensure your vehicle is on a level surface, parked securely with the wheels blocked. Also make sure your heater is turned all the way to “hot” and the fan is blowing.

2.) While radiator is cool, remove radiator cap. Position your drain pan under the radiator drain. Open the radiator drain and allow coolant to flow out until it stops. If your vehicle is equipped with an engine block drain, position your drain pan and open that drain allowing the engine block to completely drain as well. Dispose of the used antifreeze at your local auto parts store or hazardous material transfer station in accordance with local law, and to protect our environment.

3.) Fill the cooling system completely with water. Start your engine and allow it to run at idle for 10 minutes, or until it has reached normal operating temperature. Be sure to keep a careful eye on your engine temperature gauge during this step. If your vehicle begins to overheat, turn the engine off immediately and let it cool.

4.) With your radiator and engine cool again, drain the water from the cooling system just like you did in step 1 draining the radiator and the block.

5.) With all the drains closed, add BlueDevil Radiator Flush to your radiator and top off the system with water. Once you have about 2 gallons of water in the cooling system start the engine and let it warm up. As it warms continue to add water to the radiator until you see water flowing through the radiator and the upper radiator hose is hot. Top off the system with water and replace the radiator cap.

6.) Let your engine idle with the radiator flush inside for at least 10 minutes, but time and weather permitting run your vehicle for 3-6 hours with the radiator flush and water solution in your cooling system. This will provide a deep clean and restore your cooling system to top efficiency. While driving, keep an eye your temperature gauge to make sure it doesn’t overheat and make sure the outside temperature does not drop below 32 degrees to prevent freezing.

7.) With the engine again cool, drain the Radiator Flush and water mixture. With all the drain plugs open, flush the system thoroughly with water allowing it to flow into the radiator cap and out of the radiator and block drains until clear water runs freely out.

8.) Close all drain plugs and add the manufacturer’s recommended type and amount to your radiator. Just like step 5, you may have to add most of the antifreeze, then start and run the engine up to operating temperature to allow coolant to flow through the engine and radiator removing bubbles and allowing room for all the antifreeze.

It is best to purchase all the products you will need before starting any project. You can pick up the required amount of antifreeze at your local dealership or auto parts store.