Use a sealable container, or have one handy to transfer the fluid into, so that you can safely dispose of the old radiator fluid later on. The coolant contains antifreeze and other chemicals which are toxic. Never pour it down a drain.
Check your vehicle’s owner’s manual if you aren’t sure where the temperature control is or how to set it to the highest setting.
Use a rag to remove the pressure cap if it is hard to twist and pull off. If there is no drain cap on your radiator, then disconnect the bottom hose at this point to let the radiator fluid drain out that hole.
Poke a piece of wire or a wire brush into the hole and wiggle it around to clear it if the liquid does not start draining out right away on its own.
Contact a local recycling center, hazardous waste disposal company, or mechanic to dispose safely of the old radiator fluid.
If you see a screw on the clamps that connect the hoses, you need to loosen the screw to disconnect the hoses. If there is no screw, then the clamp is a tension clamp that you need to squeeze with pliers to loosen.
Make sure that the hose is held really tightly in place in order to efficiently flush the radiator.
Use a rag to twist the cap back on tightly if it is hard to do with your bare hands.
You won’t be able to tell if the water is completely clear just by looking at it flowing out the bottom. There are small sediments that you can only see in still water.
In most cases, it will just take a few minutes for the water to run clear.
You can also replace the hoses at this point if either of them are damaged or worn out. You can get new hoses at an auto parts store.
The normal temperature is that an engine operates at is about 220 °F (104 °C).
The new coolant will usually be good for 2-3 years, after which you will need to replace it again.
