How to Replace Your Car's Radiator Fluid

January 27, 2012

Over time, the radiator fluid in your car will become dirty and contaminated and will need to be replaced. How often you replace the radiator fluid depends on your driving environment, as well as the way you drive your vehicle. It helps keep your car engine cool while it's running and driving in very hot conditions adds strain to the system. It also protects your vehicle in the winter if you live in a very cold area, and helps to keep the engine block from freezing up and being damaged. You should change the radiator fluid at least once a year or according to the changing seasons.

Tools and Materials

  • Antifreeze
  • A bucket or plastic container
  • A dry towel
  • Work gloves
  • A screwdriver or wrench

Turn off the Engine
Turn off your car and allow it to remain off for a couple of hours. Make sure that the engine has completely cooled down before draining the radiator fluid. If you try to work on your radiator while the engine is still hot, the fluid may overflow and you could be burned or injured.

Remove the Radiator Cap
After the engine is completely cooled, place the dry towel on the radiator cap and loosen it (make sure to wear your gloves), but do not remove it just yet. Allow the pressure from the radiator to completely escape through the loosened radiator cap before removing it all the way.

Locate the Radiator Drain Plug
Locate the radiator plug on your vehicle. It can usually be found on the underside of the radiator tank. It will usually look like a cylindrical plug that has a screw, a T-bolt or a nut head. Once you have located the drain plug, place the bucket or plastic container directly underneath it.

Remove the Radiator Drain Plug
Turn the radiator drain plug counterclockwise and remove it. Allow the old radiator fluid to completely drain into the bucket or plastic container before continuing.

Reinsert the Radiator Drain Plug
After the old radiator fluid has completely drained into the container, reinsert the plug and turn it clockwise and tighten securely.

Add New Antifreeze
Add a mixture of half antifreeze and half water to the radiator until it's completely full. Fill the radiator reserve or overflow tank with the half-and-half mixture as well.

Start the Engine
Leaving the radiator cap off, start your car engine and allow it to run for a couple of minutes until the radiator burps. This will allow the radiator fluid to settle into the cooling system and will also get rid of any air pockets that may have developed.

Refill the Radiator Again
After the radiator has burped and the coolant has settled, refill the radiator and reservoir tank to the top again.

Replace the Radiator Cap
Put the radiator cap back on and turn clockwise until it's tightened securely.

Dispose of the Old Fluid
Take the old radiator fluid to a recycling center or auto parts store. These places will be able to properly dispose of the old radiator fluid for you. Never pour the old radiator fluid down the drain or onto the ground.

How to Get Rid of Frozen Radiator Fluid

Unless your radiator fluid has the correct mixture of 50 percent antifreeze and 50 percent water, you can end up with frozen radiator fluid, or a frozen engine block. To protect the block from splitting, an engine block has freeze plugs that will pop out if the fluid inside starts to freeze.

Raise the Temperature of the Cooling System

Once the radiator fluid has frozen, the only way to remove it from the cooling system is to raise its temperature. Unless your vehicle is in your garage, you need to have it towed to an enclosed area for defrosting. Since most garages do not have their own heaters, rent or buy a space heater, and aim it at the engine compartment of your vehicle. You can add the help of several high wattage hair dryers, which can be used to concentrate heat to specific locations. Use a hair dryer to concentrate heat to the radiator cap, and hose connections. Open the cap, and disconnect hoses as soon as you are able.

While the vehicle is defrosting, start inspecting the engine block and radiator for splits. Additionally, check the engine block to see if the freeze plugs have popped. Remember, popped freeze plugs mean you have frozen radiator fluid. If possible, position a hair dryer to blow against the openings where the freeze plugs were. Be mindful of defrosting radiator fluid, and keep it away from sources of electricity. Additionally, you need to place drip pans at any location where defrosting radiator fluid will drip.

Flush the Cooling System
Once the vehicle has had a chance to adequately defrost and drain, the cooling system should be flushed. Unbolt the thermostat housing (water jacket) from the engine, and remove the thermostat (it will need to be replaced). Replace and bolt the water jacket to the engine. Ensure you have placed drain pans at all of the openings to catch the flushed fluids. Using warm water (if possible), pour into the water jacket opening. When clear, clean water pours from the freeze plug openings, the engine has been flushed. If the radiator was not damaged during the freeze, it will need to be flushed as well. Close the radiator drain plug, and fill the radiator with clean, warm water. Open the radiator drain plug and allow the fluid to drain. Repeat until there is only clear water draining from the radiator. Thoroughly rinse all hoses that are re-usable.

Reassemble and Refill the Cooling System
Once the flushing procedure has been completed, remove the thermostat water jacket, and install the new thermostat and gasket. Install new freeze plugs. Reconnect all radiator and heater hoses, and close the radiator drain plug. Refill the cooling system with the correct mixture of antifreeze/coolant in accordance with your owner's manual instruction.

Costly and time-consuming radiator and engine block freeze outs can be avoided if the correct mixture of antifreeze is used in the cooling system. People living in areas of extreme cold or heat should use a 70/30 mix of antifreeze and water.