Engine coolant runs through your entire cooling system to and from the radiator. The water pump is what moves the coolant through the system. The radiator uses cooler air to bring down the temperature of the coolant. This diagram offers a more detailed look at the process and shows all the parts involved.
Also known as antifreeze, coolant is the red or green liquid in your radiator and throughout your cooling system. Radiators are usually filled with a 50/50 mixture of coolant and water. It keeps the water in your radiator and engine from freezing in cold temperatures. It keeps the water from overheating in all temperatures. It helps to lubricate the components in the cooling system.
A flush is different from a simple drain and refill because it replaces all of the old coolant, and flushes out sludge, rust, and dirt buildup. A drain and refill entails only draining and refilling the coolant in the radiator. Flushing the coolant in your vehicle's cooling system is a great way to help maintain a healthy engine.
As coolant gets older, it begins to lose its protective properties and doesn't do its job as well as it used to. Sludge, dirt and rust can also buildup in the cooling system which can cause a blockage in a hose or line. Having fresh coolant and a clean system better protects and cools all components.
There are a number of factors that determine how often to have a coolant flush, including the size of the engine, the vehicle's mileage, the climate you drive in, the age of the current coolant, the type of coolant in your system, and the manufacturer's recommendation. Most vehicles require a coolant flush every 24,000 to 30,000 miles, or every 2 to 3 years, whichever comes first. Check your owner's manual to see what your vehicle’s manufacturer recommends