Most hose manufacturers recommend having the hoses be replaced every four years. The incidence of failure rises dramatically after the fourth year of service.

The hard part about changing belts and hoses is the idea thatit is preventive maintenance BEFORE they fail. Few people do, yet they could save themselves a lot unnecessary grief and expense if they would.

How many times have you seen someone on the side of the road with their hood up? Smoke is billowing out and they are just sitting there.

Rubber hoses deteriorate with age. Tiny cracks develop in the rubber which eventually cause the hose to split, blister or leak. Oil contamination and atmospheric ozone can accelerate the process.

Engine vibration and motion can cause hoses to wear if they are to short or rub against other parts. This applies to fuel, vacuum and emission hoses as well as coolant hoses.

A visual inspection will often uncover bad hoses. Pinching hoses to check for age cracks, brittleness, or mushiness can also help locate hoses that need to be changed.

However, neither technique will reveal all the hoses that might need replacing because of wear as much from the inside out as they do from the outside in.

A hose that appears okay on the outside may actually be on the verge of failure because of internal deterioration.

According to research done by one hose manufacturer, internal corrosion caused by electrochemical degradation is the primary cause of cooling system hose failure.

The coolant acts like an electrolyte and allows a current to flow between the engine and radiator. This causes micro-cracks to form inside the hose which eventually leads to pinhole leaks and weakening of hose fibers.