How to Flush Your Radiator

  • 2-4 hours
  • Beginner
  • 10-40
What You'll Need
Phillips head or flat head screwdriver
Coolant receptacle
Fresh coolant
Radiator flush product

One of the most common mistakes car owners make is overlooking the care and maintenance of their cooling system, making a proper radiator flush a crucial aspect of keeping your vehicle well maintained. Typically, the only time car owners even think about their car's cooling system is either at the beginning of winter months, when a small percent of these owners check their antifreeze level, or when the cooling system overheats and causes problems. Realistically, your radiator should be flushed at least every other year to reduce the build-up of deposits in it. Some auto maintenance manuals suggest flushing every year. To keep your cooling system operating as it should, follow these 5 steps to flush your radiator.

Step 1 – Preparing to Drain Old Coolant

You will need to drain any old coolant in your radiator, because as your car's coolant runs through the car's cooling system, it collects deposits that can damage your car's cooling system. Before you drain any coolant from your car's system, be sure to park your car where coolant, if accidentally spilled, will not run onto the ground or into a storm drain. To drain old coolant, first be sure your car's engine and coolant are not hot. Then, open the radiator cap. To be safe, use a rag to hold the cap as you unscrew it.

Step 2 – Draining the Old Coolant

Locate the drain plug on the bottom of your car's radiator and place an empty, wide-mouth container under it to catch old coolant that drains from the radiator. The container will need to be large enough to hold liquid that will be drained twice from your car's radiator. Using a screwdriver, open the drain plug as wide as possible, then wait until the old coolant has completely drained from the radiator.

Step 3 – Adding the Flush Product to the Radiator

Close the drain plug. Add the flush product and fill the remainder of the radiator with water. Screw your radiator cap on tightly, start your car's engine, and allow it to run until the temperature gauge shows a normal engine temperature. When the temperature gauge shows normal, turn your heater on, set controls to the hottest temperature and highest fan setting, let the engine run for 10 minutes, then shut off the engine and let it cool until the radiator cap is cool enough to be touched without it burning your hand.

Step 4 – Draining the Radiator Flush Product

Again, loosen the radiator cap and drain plug and allow the flush product to drain into the container holding the old coolant. Do not drain it onto the ground, your driveway, or your garage floor as the coolant is extremely toxic to children and pets.

Step 5 – Refilling with New Coolant

With your radiator drain plug closed tight, fill the radiator with fresh antifreeze. Use premixed 50/50 coolant (50% water, 50% antifreeze) or follow directions you find in your car owners manual. When the radiator is full, replace the radiator cap, let the car run, and check for leaks.