Oxygen sensors are very simple to replace. From time to time, you will come across a rusted O2 sensor that is stuck and refuses to loosen up. In this article, you will find a few methods you can use a loosen and unscrew an "impossible" to remove oxygen sensor.
How to remove/loosen an oxygen sensor
It is very important to use the proper oxygen sensor socket for your particular vehicle. Some cars require special oxygen sensor tool to remove them.
The O2 sensor is located on the exhaust manifold or exhaust system; there is a good chance it will accumulate rust and eventually get stuck. The first method I recommend is using penetrating oil such as liquid wrench or PB blaster. Spray the penetrating oil on the O2 sensor and allow it to sit for a good 20-30 minutes. Afterward, use an O2 sensor socket wrench and remove the sensor.
Sometime, due to tight spaces; you may have to use a regular metric or standard wrench. Some of the common wrench sizes are 22mm and 27mm or 7/8”. A stubby wrench may also be useful if the space is extremely limited.
Warm Up Engine
It is always easier to remove the oxygen sensor when the exhaust is hot. The reason this method works is because metal expands with heat, therefore, making O2 sensor removal easier. Moreover, this method only works when the oxygen sensor is an open location and easy to get to. Run the engine for a good 20 minutes until the exhaust system and the catalytic converter is hot. Place the vehicle on jack stands or a lift.
Use a propane torch. Propane is a great way to quickly heat up the O2 sensor. Again, place the vehicle on jack stands or a lift; Make sure to use propane in open spaces. Be careful not to use the propane torch around flammable materials as this is dangerous. Heat up the O2 sensor for a good 30 seconds. Allow the O2 sensor and exhaust manifold or exhaust system to naturally cool. Do not throw water on the O2 sensor as this can crack the exhaust manifold or exhaust system when it is cooled too fast. Use an appropriate O2 sensor socket wrench and remove the O2 sensor.