How to Clean a Radiator With Muriatic Acid

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Things You'll Need

  • Oil drain pan

  • Muriatic acid

  • Water hose

  • Socket set

  • Pliers

  • Screwdriver

  • Car

  • Plastic 1-gallon bucket

  • Plastic 55-gallon drum with lid

  • Rubber gloves

  • Face shield

  • Disposable protective suit

The radiator protects your engine from overheating.

A radiator is a part of the cooling system of your car's engine. It allows water or coolant to circulate through small tubes that are cooled by air coming in through the grille of the car, as well as by the cooling fan. This water then circulates through the hot engine, cools off the metal parts inside and carries away the heat, only to be cooled again on its next trip through the radiator. Debris from the heated metal and the water itself will occasionally clog the radiator, making it unusable. A weak muriatic acid flush will cure this problem.

Step 1

Remove the lid from the oil drain pan. Slide the pan under your car. Remove the fill cap from the top of the radiator. Open the drain cock on the bottom of your car's radiator with the pliers. Loosen the clamp on the upper and lower radiator hoses with your screwdriver. Slide the clamps onto their respective hoses and pull each hose away from the radiator.

Step 2

Use your socket set to remove the retaining bolts from the outer edge of the radiator. Pull the radiator free from the car. Twist the drain cock on the bottom of the radiator closed. Remove the lid from your plastic 55-gallon drum. Hold the radiator upright over the barrel with the bottom edge of the radiator resting on the lip of the barrel.

Step 3

Pour 2/3 gallon of water into the plastic bucket. Add 1/3 gallon of muriatic acid to the water. Pour the mixture slowly into the fill hole on the top of the radiator. Be careful not to spill any of the acidic mixture. Continue mixing Let the mixture remain in the radiator for five minutes. Open the drain cock and allow the acidic mixture to drain into the 55-gallon drum.

Step 4

Hold the end of the water hose in the fill hole on the top of the radiator. Turn on the water supply and allow water from the hose to flow through the radiator to flush the acid out of the tubing inside. Let the water flow through the radiator for five minutes. Be sure to hold the radiator upright, and allow the contents to drain into the 55-gallon drum.

Step 5

Slide the radiator in place under the hood of the car. Replace the retaining bolts in the appropriate holes. Twist each screw in place by hand to prevent cross-threading. Tighten each bolt with the appropriate socket from your set. Slide the upper and lower radiator hose into place on the radiator. Maneuver each hose clamp to the end of its hose. Tighten the clamps with your screwdriver.

Step 6

Dump the contents of your oil drain pan into the 55-gallon drum. Fasten the lid onto the drum. Close the drain cock and fill the radiator with water or a 50/50 mixture of coolant and water. Start the car and watch the level of water in the radiator through the fill hole. Top off the water as the level lowers when the radiator fills the engine block. Twist the fill cap onto the radiator and turn off the car's engine.


Rubber gloves, a face shield and a disposable protective suit must be worn when working with acid or chemicals of any type.


Danny Donahue

After learning electronics in the U.S. Navy in the 1980s, Danny Donahue spent a lifetime in the construction industry. He has worked with some of the finest construction talent in the Southeastern United States. Donahue has been a freelance writer since 2008, focusing his efforts on his beloved construction projects.