How to Flush a Rusted Radiator How to Flush a Rusted Radiator

What You'll Need
Bucket with a 2 gallon capacity
Coolant/Antifreeze
Radiator cleaner
Water
Hydrometer or test strips

An efficient radiator cools your engine by circulating coolant through its pipes. It is important to keep it free of rust or blockages and it is even suggested that you flush and refill it every six months. It is a easy to learn how to flush a rusted radiator but you will find that it is a bit messy so be sure to wear old clothing, keep children and pets away from your work area and stay away from storm drains in case of any spills.  Whenever working on your radiator it is important that the engine is cold. Below you will find a step by step instruction list on how to flush your rusted radiator.

Step 1 – Drain Coolant from System

Park your car on a flat surface, turn on your heater and then turn off you car. Be sure to set your emergency brake and place your car in park or in gear if a manual transmission. Let the engine cool.

Set your bucket under the radiator plug and open it. Allow all the coolant to drain into the bucket. If your engine also has plugs in the engine block, you can remove those to so that you can drain any remaining coolant. Once the flow has stopped, replace all the plugs.

Step 2 – Fill the Radiator with Cleaner

To remove the rust and sediment left in your system, you will now need to fill the radiator with radiator cleaner. You will use the mix of radiator cleaner and water as specified by the product’s manufacturer.

Step 3 – Run the Car with the Heater on

Turn on your car and turn on the heater to the high setting, following the instructions from the product’s manufacturer for the proper length of time to let it run.

Step 4 – Drain the Cleaner

After you have run the heater for the proper time, you once again need to let the engine cool. Once it has cooled, place your empty bucket under the plug(s) again, remove them, and as before, allow all of the cleaner to drain out of the system.

Step 5 – Fill the Radiator with Water and Repeat

You need to flush the cleaner fully out of the system by following steps 2 to 4 again, this time using only water in the radiator. Again, run the car with the heater on, allow the car to cool, and drain all the water out of the system once again by the plug(s).

Step 6 – Refill the Radiator with Coolant/Antifreeze

Always consult with the owner’s manual of your car for the proper coolant to water ratio. Being sure all the plugs are in, fill the radiator with the mix and then fill the reservoir tank to the marked level (usually found on the side of the tank) with a 50/50 mix of coolant to water. 

Step 7 – Run the Engine and the Heater

Start the car and run the engine to what is roughly normal operating temperature. Run the heater on high again. This will circulate the coolant throughout the system. Be sure to check for leaks. You can now drive your car as normal.

Step 8 – Test System

After several days of normal use, test the concentration of the coolant with either a hydrometer or test strips and adjust as needed.

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