What you can't see can hurt you. That's what Gates engineers discovered during four years of field testing on fleet vehicles. In these tests, they identified the primary cause of coolant hose failure as an electrochemical attack on the rubber tube compound in the hose.

The phenomenon is known as electrochemical degradation, or ECD. It occurs because the hose, liquid coolant (ethylene glycol antifreeze and water), and the engine/radiator fittings form a galvanic cell or "battery." This chemical reaction causes microcracks in the hose tube, allowing the coolant to attack and weaken the hose reinforcement.

The best way to check coolant hose for the effects of ECD is to squeeze the hose near the clamps or connectors using the following procedure:
1. Make sure the engine is cool.     
2. Use fingers and thumb to check for weakness, not the whole hand.     
3. Squeeze near the connectors. ECD occurs within two inches of the ends of the hose -- not in the middle (see Figures 1 and 2).

   Figure 1 

   Figure 2  

4. Check for any difference in the feel between the middle and ends of the hose. "Gaps," or "channels," can be felt along the length of the hose where it has been weakened by ECD.     
5. If the ends are soft and feel mushy, chances are, the hose is under attack by ECD. To avoid breakdown of the cooling system, Gates engineers recommend replacing the hose immediately.

Solving The Problem

ECD is evident in almost all cooling system hoses. The most severe damage occurs where the temperature is hottest and air is present with the coolant, which is why upper radiator hoses tend to fail first.

A replacement interval of four years for all coolant carrying hoses -- especially the upper radiator, bypass and heater hoses -- can help prevent unexpected failure from ECD. The incidence of hose failure increases sharply after four years for most vehicles. 

Earlier hose replacement is recommended for fleet vehicles such as taxis, police cars and delivery vans that are subject to significant stop-and-go driving and the resulting high engine and coolant temperatures. 

To address the damage caused by ECD, Gates developed an electrochemically-resistant coolant hose using a new EPDM (ethylene propylene rubber) formulation and special wrapped reinforcement. These new hoses are long-lasting with no ECD effect. 

In addition to providing electrochemical resistance, the new EPDM hose offers improved performance characteristics over both standard rubber hose and much more expensive silicone hose. 

In tough fleet tests, Gates hoses have gone 200,000 miles, and are still going, with no electrochemical damage. Standard hoses revealed damage and failures as early as 20,000 miles on the same fleet applications.