What is the best way to check the condition of the coolant hoses on an engine? If you answered X-ray vision, you're right. That would allow you to see inside the hose to view the tiny cracks on the inside walls of the hose where damage begins. The second best, and more realistic way, to check any coolant hose is with the squeeze test.
The squeeze test can be used to inspect any coolant hose for the negative effects of Electro Chemical Degradation (ECD), which is the primary culprit of coolant hose failure. ECD creates fine cracks, or striations, in the tube wall inside the hose. The fine cracks extend from the inside to the outside of the hose tube near one or both ends of the hose and weaken the structure of the tube. (Fig. 10)
(Fig. 10)
Regular Maintenance
Evidence of ECD depends on the quality of the hose, time and vehicle use, so there is no readily identifiable maintenance interval to follow. The squeeze test of coolant hoses should be included as part of a vehicle's regular maintenance.
To perform a squeeze test, squeeze the hose near the clamps or connection using the following procedures:
• Make sure the engine is cool
• Use your finger and thumb, not your whole hand, to check for softness
• Squeeze near the connections. ECD occurs within two inches of the ends of the hose, not in the middle.
• If the ends feel soft or mushy but the middle feels firm, the hose is under attack from ECD
Electro Chemical Degradation
ECD is an electrochemical attack on the tube compound. Different metals found in an engine system release an ionic discharge, generating 5 to 150 millivolts. The coolant contacts the various metals, picks up the charge and discharges the electrical energy into the hose. The voltage discharge initiates an electrochemical process that ultimately creates small cracks or striations (markings with parallel grooves) in the hose tube. Over time, these cracks widen, resulting in pinhole leaks and, eventually, leading to catastrophic failure. Heat does not cause the failure, but it does accelerate the electro chemical degradation process.
Inferior hoses are more susceptible to ECD. It is recommended to change these hoses every four years or sooner if used in a fleet application. Some standard hoses have revealed damage and failures as early as 20,000 miles in fleet applications.
To beat the effects of ECD, a new innovative tube material has been developed that is Electro Chemically Resistant (ECR). In testing, the ECR hose has been shown to last 200,000 miles.
In addition to ECD damage, during a routine inspection of coolant hoses, always check for any heat damage, oil damage, and abrasive ozone damage (caused by pollution attacking bonds in rubber components that appears as tiny cracks at curves and bends) of the hoses.
- Thanks to Mike Militello
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