Open the bleeder valve if present
Some automobiles have a radiator bleeder valve, which is present for the purpose of removing trapped air in the radiator. The air is mostly trapped in the upper section of the radiator since air is lighter than water and coolant, so this valve is usually found at the top section of the radiator.
Raise the car
This is very crude way to bleed the radiator dry of air as elevating the car from the front side raises your radiator to the extent that it is higher than the rest of the cooling system. This process puts pressure on the air pockets inside the radiator and causes them to be released to the atmosphere.
Take off the radiator cap and turn on the engine
One of the simplest ways to bleed your car engine is to take off the radiator cap and then fire the ignition. Some coolant may pop out of the cap, do not panic.
Keep the engine running for about 15-20 minutes as your engine needs a certain amount of time to generate enough heat to push out the trapped air in your cooling system. Keep a bottle of coolant in reserve as some coolant will be wasted during this procedure.
Flushing the container
Flushing the radiator is a good way to refresh the coolant inside the cooling system. It also helps prolong the life of the radiator as this removes dirt and other debris from the chamber. Put a bucket underneath the radiator and use a wrench to loosen the drain hole under the radiator.
Take out the bolt completely and coolant will start gushing out of the hole. Give it about 15 minutes to drain out completely. Put the drain bolt back in its place and add fresh coolant to the radiator.