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Oxygen Sensor Replacement

Quite often, a home mechanic removes a brand new oxygen sensor from the box and improperly installs it. This mistake ruins it, or at least shortens its life. When replacing the oxygen sensor, here are some tips to gain the most life possible from it:

  • Always use an oxygen sensor wrench or socket when removing and installing the sensor. These tools are designedto apply even torque to the sensor. Under no circumstances should an adjustable wrench be used on an oxygen sensor.
  •  In order to facilitate easy removal of a sensor at a later time, apply anti seize compound to the threads prior to installation. Take care to only apply a small dab to the threads, and don’t get any compound on the tip of the sensor.
  •  The wires in the sensor are delicate and can be broken or pinched. Install the oxygen sensor prior to connecting the wires to the harness. Also take care when routing the wires. Exhaust systems are extremely hot and can quickly melt oxygen sensor wires.
  •  Oxygen sensors typically come with a plastic cover over the tip. Keep this cover on the sensor until you are ready to thread it into the exhaust system. This helps prevent contaminants from entering the sensor.
  •  Remember that oxygen sensors operate at 600 degrees F or more. Even if the vehicle is not running, if the ignition is on, the sensor’s heaters will most likely be engaged and heating the sensor. Prior to removing the sensor, turn off the engine and let it cool for an adequate amount of time.
  •  When changing exhaust systems or exhaust pipes, keep in mind that the pipes are often coated with light oil when being bent. This oil is usually not cleaned off prior to installation, burns off and can harm an oxygen sensor. If the exhaust components prior to the oxygen sensor are replaced, run the engine with the exhaust sensor removed for 10 minutes to burn off the excess manufacturing oil.

So what Causes Oxygen Sensor Failure?

Oxygen sensors operate in a demanding environment and therefore are pretty tough sensors. But, as previously stated, they are considered a consumable sensor that eventually wears out and requires replacement. There are several factors that can accelerate their replacement schedule. These factors include:

  • Running the incorrect fuel type in the vehicle. Leaded gasoline, such as leaded race gas, shortens the life of an oxygen sensor to as short as a matter of hours. A sensor that has been running in leaded gasoline typically has a rusty color on the tip of the sensor.
  •  Engine oil ruins a sensor quickly by fouling the tip of the sensor, so that it can no longer sample the incoming exhaust stream. If an engine is burning oil through a mechanical issue or a PCV problem, the oxygen sensor’s performance degrades rapidly.
  •  Excessive grease, dirt, or other contaminants built up on the outside of the sensor wires reduces or eliminates the capability for the sensor to draw in outside oxygen for sampling. Sometimes the wires can be cleaned but, due to the miniscule size of the passages, they are difficult to get completely free of contaminants.
  •  If engine repairs are made and sealants are used, the sealants must be labeled as “sensor friendly.” Many sealants contain chemicals, which will foul or damage the sensor if the chemicals can reach the exhaust stream.
  •  If a head gasket or intake gasket is leaking and antifreeze is being burned in the combustion, the byproduct of the burned antifreeze is poisonous to the oxygen sensor and ruins it quickly.
  • Overly rich conditions can foul the tip of the oxygen sensor with black soot,  rendering the heater circuit or the sensor itself useless. Occasionally, the tip can be burned clean with a propane torch, but usually, the sensor has to be replaced.

About Ronnie L. Allen

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