Detecting Electrochemical Degradation
Until recently, the most common method of checking a coolant hose was to visually inspect its outside cover for signs of wear, or ballooning under pressure. Gates Corp. says this method is no longer considered completely reliable, because most hoses fail from the inside out.
In four years of field testing on fleet vehicles, Gates 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 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.
To check coolant hose for the effects of ECD, Gates recommends squeezing 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.
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.
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