Service includes a complete visual inspection of the cooling system for signs of wear, leaks and overall operation. If a leak is detected then a pressure test is also performed. Maintenance services include a coolant drain and fill or coolant flush every 24,000 miles (except Dexcool or extended life antifreeze).
Importance of Service:
Although gasoline engines have improved a lot, they are still not very efficient at turning chemical energy into mechanical power. Most of the energy in the gasoline (perhaps 7¬0%) is converted into heat, and it is the job of the cooling system to take care of that heat. In fact, the cooling system on a car driving down the freeway dissipates enough to heat two average-sized houses! The primary job of the cooling system is to keep the engine from overheating by transferring this heat to the air, but the cooling system also has several other jobs like heating the cabin of the car and helping with emissions.
What May Happen if The Service is Not Performed:
Temperatures in the combustion chamber of the engine can reach 4,500 F (2,500 C), so cooling the area around the cylinders is critical. Areas around the exhaust valves are especially crucial, and almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine. Other problems, not so severe are leaks, and no heat conditions.