Q: When Should Engine Hoses be Replaced?

asked by on November 19, 2015

When should engine hoses be replaced?

Regularly scheduled maintenance of hoses varies between vehicle manufacturers, but a good rule of thumb is to replace them whenever you have the cooling system serviced (cooling system flushed) or at 100,000 miles.

In the years past, hose technology was such that we could tell when a hose was getting soft and spongy and needed replacement. With better hose materials today, that is no longer the case. The hose interior needs to be checked thoroughly if we are to detect any degradation of the hose itself.

"What makes hoses go bad?", you may ask. This is what happens in your vehicle’s cooling system. Vehicles today are highly electrified and electronic. We use a variety of materials in their manufacture. In the engine cooling system alone, we use (or have used) iron, aluminum, brass, tin, steel, and rubber. Using these dissimilar metals and rubber, then add coolant and an electric current, now we have a perfect storm of potential system failure.

We don’t purposely add electricity to the cooling system, but it happens anyway because we use the engine block, cylinder heads, and intake manifold as part of the vehicle’s electrical circuit. Therefore, as current passes through these engine components, current also passes through the coolant and attacks the interior walls of the hoses, causing the hoses to erode. This process is called electrolytic erosion. This same process causes radiators and heater cores to leak, also, by eating away the solder that holds them together.

How do you know when to flush your cooling system to prevent the ill effects of electrolytic erosion? Here’s an old mechanic’s trick: take a voltmeter and set it on the DC volts scale. Start the engine and let it idle. Remove the cap from the degas bottle (or radiator) and place the red (positive) lead into the coolant of the engine. Place the black (negative) lead on the negative post of the battery. Look at your voltmeter. If it reads greater than 0.5 volts DC, it’s time to flush your cooling system. This small amount of voltage is sufficient enough to eat away the solder in the joints of the radiator and heater core, and weaken your hoses from the inside.

Should you have any other questions or need help servicing the cooling system of your vehicle, consider having it done by a certified mechanic. Being stranded in the middle of nowhere with a broken car is not fun. Been there, done that.

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