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Why Is My Vehicle's Exhaust Pipe Rusting?

Why Is My Vehicle's Exhaust Pipe Rusting?

3rd Apr 2020

vehicle exhaust pipe

Exhaust Pipe Rust

Does your vehicle suffer from a rusty exhaust pipe? Because they are typically made of iron or steel, exhaust pipes can rust. It made not happen overnight. Eventually, though, oxidation can set in that results in your vehicle's exhaust pipe to rust. By understanding why your vehicle's exhaust pipe is rusting, however, you can take preventative measures to discourage it.

Faulty O2 Sensor

If your vehicle's oxygen (O2) sensor is bad, it may cause the exhaust pipe to rust. The O2 sensor, of course, is responsible for measuring the amount of unburned oxygen in the exhaust. Using this information, your vehicle's computer will determine an appropriate ratio of fuel to air. If the O2 sensor is faulty, though, it may cause an excess amount of fuel to enter the engine's combustion chamber -- a condition known as running rich. With a rich-running engine, an excessive amount of unburned fuel will remain present in the exhaust, which over time, may cause the exhaust pipe to rust.

Blown Head Gasket

A blown head gasket can cause your vehicle's exhaust pipe to rust as well. With a blown head gasket, some of your vehicle's coolant may enter the combustion chamber where it mixes with fuel and oxygen. As the coolant burns, it will turn into vapor that's ejected through the exhaust. The constant stream of coolant vapor going into and out of your vehicle's exhaust may eventually cause the exhaust pipe to rust.

Cracked Engine Block

Another possibility is that your vehicle has a cracked engine block. Like with a blown head gasket, a cracked engine block can cause coolant to enter the combustion chamber, depending on where the crack is located. With both of these conditions, coolant will enter your vehicle's exhaust where it adds moisture to the exhaust pipe. The presence of moisture, of course, makes your vehicle's exhaust pipe susceptible to rusting.

Driving on Salted Roads

It's not uncommon for cities and municipalities to deice their roads during the winter using salt. Salt lowers the freezing point of water. Therefore, spraying salt on roads during the winter helps to prevent the formation of ice. The downside, however, is that salt stimulates rusting and corrosion. If you salt and water on your vehicle's exhaust pipe, it may rust.

If your vehicle's exhaust pipe has rusted, you should consider replacing it. By choosing a high-quality stainless steel exhaust pipe, it will be naturally protected against rusting.