The Heat Is On

With the reduction in engine compartment size, coolant hoses are prone to failure due to the prevalence of factors such as heat, abrasion and oil. In addition, new conditions arise, such as electrochemical degradation.

Gates has determined that electrochemical degradation, or ECD, results when the hose, liquid coolant (ethylene glycol antifreeze and water), and the engine/radiator fittings form a galvanic cell or "battery." This reaction causes microcracks in the hose tube allowing coolant to penetrate into the reinforcement. 

Accelerated by high-heat and flexing, the hose can develop a pinhole leak or rupture under normal pressure. This possibility of hidden reinforcement failure is one of the best reasons for replacing coolant hoses every two to four years. 

To address the damage caused by ECD, Gates has developed an electrochemically-resistant ECR coolant hose using a special EPDM (ethylene propylene rubber) formulation.

What To Look For

When inspecting a coolant hose for damage, make sure that the hose connection from the radiator to the engine is not kinked, and that it is not touching hot or moving engine parts or sharp edges. A kink can reduce the flow of coolant and cause the engine to overheat. The sharp surface may eventually cut or abrade through the hose, resulting in a loss of coolant. If the hose is resting on or will come into contact with a sharp surface, or is near a heat source, try one of the following:
1. Reroute the hose away from the point of contact;

    

2. Wrap protective sleeving (a slit piece of old hose, or emission control ducting for heat shielding) around the new hose at the point of contact;

    

3. Slightly twist the hose on one or both spouts to reroute the hose away from the surface.

Oil is another enemy of rubber hoses. A hose damaged by oil is swollen, soft and sticky. If the oil leak is external, eliminate the oil leak or try to reroute the hose. 

Sometimes the oil damage comes from within the hose. If the hose becomes swollen, the oil inside the hose is excessive. Check the transmission system for leaks into the radiator from the transmission cooler. 

Finally, check each clamp connection for leakage. Tighten any loose clamps and replace any that are defective.

Replacing A Hose

Gates engineers recommend that all coolant hoses be checked when the system is being flushed and antifreeze replaced -- about every two years -- or whenever servicing of the radiator or water pump is required. Hoses showing obvious signs of wear, and those more than four years old, should be replaced immediately.

Most EPDM hoses tend to bond to metals, so removal of coolant hoses from fittings must be handled carefully. It is important to avoid forcing or prying a hose to prevent damaging the fitting. Instead, use a sharp knife to cut off a hose (see Figure 1). 

Figure 1  

 

Always check the spout to be sure it is not distorted or corroded. There should be no sharp edges, or burrs, which could damage the hose. Always clean the neck of the spout with a wire brush or emery cloth (see Figure 2). 

Figure 2  

 

When installing a hose, dip the ends in coolant to lubricate it and slip clamps over each end. In cold weather (25¡F to 30¡F), the hose may be stiff. Warm the hose with hot water. 

After slipping the clamps on the hose, push the hose onto the spouts, installing the engine end first. If the hose does not fit properly, remove it and reverse the ends. Whenever hose replacement is required, it's a good practice to also replace the clamps. 

Finally, tighten the hose clamps, and refill the radiator to the recommended level. Also, check the vehicle's owners manual. Certain vehicles must have all the air bled from the system and have bleeder valves to do so, usually located on the thermostat housing.

Types Of Hoses

Today, one hose often is designed to fit a number of applications, so occasionally a new bend or twist may be introduced to absorb engine vibration.

More than 90% of replacement radiator hoses are curved or factory molded to fit specific applications. Because of parts' consolidation, many have cut-off marks showing where to cut the hose to fit a number of applications. The hose manufacturer's catalog will reference the marks to use, or will note that the hose must be cut to fit. 

Some heater hoses are factory molded into shapes to fit specific applications, while others may include special wire spines that allow them to be formed into various shapes. Molded shapes often are necessary for routing coolant hose in crowded engine compartments. 

Gates and other manufacturers offer a factory-molded heater hose to fit most popular cooling systems. Formable heater hose also can be used.