A Ford owner recently towed their vehicle into our shop. An engine fire caused considerable damage. While repairing the damage, it was obvious the problem began with a failed hose, on an emissions sensor.
To most folks, one automotive hose looks very much like another. They may give little thought, beyond looking for the right length and diameter. This can be a big mistake. Automotive hoses have many specifications and mixing applications can be costly.
The parts of a hose
Manufacturers normally construct automotive hoses in layers. An outer covering protects the internal components from environmental concerns. They choose a material resistant to the forces acting on the hose. For instance, a hose in the engine compartment must resist heat and oil. Hoses exposed to outside elements may need ozone or UV light resistance.
The liquid or gas moving through the hose and other factors determine the makeup of the inner lining. This is the part of the hose that contacts the material the hose conveys. Radiator hoses transport hot engine coolant. Ethylene propylene diene monomer or EPDM is an excellent choice for such a lining. This material easily holds up to hot engine coolant. Exposed to petroleum, EPDM would very quickly fail. We make fuel lines with a different material.
Cords or belting surrounds the inner liner and adds strength to the hose. The number of cords varies. A vacuum hose may have none but a brake hose may have several. The operating pressure determines the construction needed. Fuel lines designed for carburetors operate at 15 PSI or less. A fuel hose in an injected vehicle may hold more than 75 PSI in operation. We expose brake hoses to loads up to 2000 PSI.
Other hoses may handle very hot gases. Ford uses special silicon hoses to connect the DPFE sensor to the exhaust system. They may look like a vacuum hose, but the material in these hoses can resist several hundred degrees of heat. Replacing this hose with a vacuum line caused the above fire.
Engineers use silicon hoses in several critical locations. Sometimes they mark these hoses and often they do not. The best way to be certain of a proper replacement is to buy the original equipment manufacturer or OEM part. They design other hoses to resist extreme pressure. Examples include power steering hoses and other hydraulic lines. These hoses may have several layers of belting for strength. Substitution of standard hoses for these applications can cause disastrous results.
The correct size is a must
Engineers design hoses of specific diameter and flow rate to fit applications. For instance, they sometimes internally restrict hoses to limit flow. This is often the case with heater hoses. An unkept cooling system may result in a debris buildup. This debris may plug the orifice in a heater hose and stop the heater from operating. A well-meaning technician notices the blocked hose and replaces it with a larger, free flowing hose. The heater works well, but six-months later the heater core leaks into the passenger compartment. Increased coolant flow eroded the core. The replacement core lasts about 18 months and the problem recurs. They restricted flow for a reason and changing the hose changed the design. With hoses, some may be good, but more is not necessarily better.
Counterfeit and substandard hoses
They often label high pressure hoses with the SAE specifications. This would be good, except no one checks hoses in the market place to see if they meet the standards on the label. Cheap offshore hoses and worse counterfeit hoses may get into the replacement market. Buying hoses online may seem like a bargain, but failure can be devastating. Only buying OEM or a quality name-brand hose makes far more sense.
Another problem is substandard hose clamps. These are widely available at discount part houses and mass merchandisers. Cheap hose clamps can break and leak. A broken cooling system clamp may overheat an engine. Determining the difference in two clamps is difficult, without test equipment. Here too, purchasing only name-brand quality hose-clamps is wise.
Hoses and hose clamps may be a simple subject, but a huge amount goes into the proper part. Play it smart and use the right hose.