Radiator hoses are used to connect a stationary radiator to the car's moving engine. Regardless of how smooth the engine runs, it is subject to vibrations and movement. If the connections between the radiator and engine were rigid, this movement would cause the connections to fail. Because of this, flexible hoses are used; however, these hoses are moulded in specific configurations to fit around fan blades, exhaust components and other obstructions. Periodic inspection is important to ensure that the hose quality is intact.
Visual hose inspection
Raise the bonnet of the car and visually inspect the radiator hoses. Notice their routing and make sure they are not interfering with any moving parts or hot exhaust pipes. Some hoses have nylon mesh covering them while others are equipped with small, metal shields to deflect heat. Hoses that are misrouted often rub against pulleys or sharp metal edges. As the engine moves or vibrates, the hose is abraded and fails.
Testing the upper hose
Squeeze the upper radiator hose and notice how resilient and flexible it feels. It should feel firm, stiff and rigid. Soft, weak or pliable hoses are not acceptable and will likely fail. Also reject the hose if it is discoloured and faded. The financial consequences of an overheated engine far exceed those of replacing the hose.
Testing the lower hose
Squeeze the lower radiator hose while at the same time feeling its circumference, paying particular attention to areas that are hard to see. Engine oils and road grime often tend to build up in one particular area, caused by the fan and pulleys slinging these contaminates against these areas. The lower hose will feel much more rigid because of a steel spring embedded inside the hose. This design prevents the lower hose from collapsing and closing off water flow because of the forceful suction of the car's water pump. Replace the hose if any failures are indicated during the inspection.
Inspecting the heater hoses
Examine the flexible heater hoses that go from the engine to the inside of the car. They are much smaller -- about the size of a garden hose -- and they carry water that has been heated by the engine to inside the car, where it is used to provide heat. They are moulded and flexible for the same reasons as the main radiator hoses. These hoses are often overlooked during inspection, and the same inspection criteria applies.