Are O2 Sensors Reverse Threaded?

Have you tried to loosen an O2 sensor, and it couldn’t budge? Or maybe you don’t know the right way to turn it? I have tried to loosen the O2 sensors several times, but they won’t budge. That’s not because I don’t know which way to turn it but because most O2 sensors prove stubborn to come loose.

So, whether you are asking, are O2 sensors reverse threaded or wondering why the O2 sensor is not coming loose, you’ll get your answers in this article. Here, I’ll explain O2 sensor removal tricks, which way to turn it, and how to remove O2 sensor without a tool. Grab a seat while I uncover all you need to know.

are all oxygen sensor threads the same

How do you loosen an O2 sensor?

Removing an O2 sensor is quite simple. It is the same approach as loosening any bolt, nut, or threaded component like spark plugs, lug nuts, axle nuts, et cetera.

To loosen an O2 sensor, grab the oxygen sensor hex edges with an O2 sensor socket or a flat spanner and turn the spanner counterclockwise. In some cases, the O2 sensor will unscrew easily. But if it doesn’t, apply penetrating oil on it and turn the spanner counterclockwise.

Here’s my favorite trick for loosening a stuck O2 sensor. I usually apply penetrating oil on the O2 sensor and allow it to sit for a minute or two before slacking it. Once I slack the sensor, I’ll re-spray the penetrating oil and turn the sensor back and forth. When it feels free, I continue turning it counterclockwise until it becomes hard again. I will apply the oil again and turn the sensor back and forth until it becomes free to loosen. 

Another way to lose a stuck O2 sensor is to start the vehicle and allow it to heat up or heat the O2 sensor with a blow torch. The heat will weaken the rust, grime, and junk, causing it to stick on the thread. You still have other options if you don’t have extra bucks for penetrating oil.

The thing is, the majority of oxygen sensors are hard to come out. You either heat up the car or use a blow torch on the sensor, or apply penetrating oil on it for easy removal. So, if you are asking how to remove stuck O2 sensors, now you know.

What thread does an O2 sensor have?

Vehicles are designed by different manufacturers with different technologies and engineering. So, the O2 sensor has different thread sizes, depending on what the manufacturer uses at that moment. Hence, it is essential to consult your owner’s or service manual to know the exact oxygen sensor thread size.

However, the majority of O2 sensors have a thread size of M18x1.5. This means that most oxygen sensors have a metric thread of 18mm and a pitch of 1.5mm.

Are o2 sensors reverse-threaded?

As a certified automotive mechanic and experienced car writer, I can confidently say that O2 sensors are not reverse-threaded. They are threaded clockwise and loosen counterclockwise, which is the standard way of tightening and losing any threaded object.

This means you have to turn the spanner towards the right hand when tightening and towards the left when losing them. Simply put, O2 sensors are righty tighty and lefty-loosey.

However, a tiny fraction of O2 sensors may be reverse threaded, meaning they are threaded counterclockwise and loosen clockwise. In other words, a few O2 sensors may be righty-loosey and lefty-tighty. Hence, it is essential to consult your owner’s manual if you are in doubt about which way to lose the oxygen sensor in your exhaust system.

are o2 sensors reverse threaded

Is there a special tool to remove an O2 sensor?

Yes, there’s a special tool for removing O2 sensors. The best and easiest way to remove the O2 sensor is by using a 0.95 cm or ⅜ in ratchet wrench fitted into a 2.2cm or ⅞ in O2 sensor wrench.

If you don’t have these tools, an open-end wrench will do the job. Kindly note that oxygen sensors are known for proving stubborn before coming off. So, expect the stubbornness and apply penetrating oil on it for easier removal.

Should I put anti-seize on O2 sensor threads?

Apply an even layer of anti-seize on the threads of a new O2 sensor so it can easily come off the next time you want to lose it.

Most importantly, do not coat the threads with too much anti-seize so it won’t contaminate the sensing areas of the sensor. Also, only use an anti-seize that says “sensor safe.” I recommend using dielectric grease. It is best for all electrical and sensing works.

How to fix o2 sensor threads

There are two possible ways of fixing an O2 sensor thread. They include cleaning the threads with a tap and rethreading the threads.

Tools and items needed

  • O2 sensor
  • oxygen sensor thread repair tool

Cleaning the threads

The first step in fixing an oxygen sensor is cleaning the threads. The tap on the repair kit can be used externally with a flat spanner or internally with a wrench. To do this, remove the old oxygen sensor and get the repair kit close by.

Insert the M18x1.5 into the oxygen sensor hole and clean it by threading the tap. Ensure you position your hand properly and thread with caution. Loosen the tap after cleaning the threads.

Now, install the new oxygen sensor. You can use the old sensor if it is still good and the thread is okay. Proceed to the next step if the damage on the thread is too much.

Repair the threads

If the damage on the threads is too much, then you have to rethread them.

Once again, the tap can be used through an internal square or external hexagon. Cut the threads with M20x1.5 by threading the solid inserts. Ensure you cut all the threads before removing the tap.

Put a solid insert on the oxygen sensor and screw it into the hole. Unscrew the sensor, put a wire insert into the M18x1.5 tap, and thread it into the hole. Lastly, remove the tap and install the oxygen sensor. Pat yourself on the back if you get it to this point. Here’s a visual presentation on how to fix oxygen sensor threads.

If you are wondering, are all o2 sensor threads the same? The answer is no. But the majority of them are 18mm, and that’s why I used the sockets in my explanations.

Final Words

In summary, O2 sensors are not reverse-threaded. They follow the standard right-hand thread, meaning you turn them to the left-hand side when losing them and the right-hand side when tightening them.

Remember to apply a slim layer of anti-seize on the O2 sensor when tightening it to prevent it from seizing up during the next removal. Always apply penetrating oil or heat the exhaust before removing the oxygen sensor.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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