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O2 sensor removal

Am trying to extract the heated oxygen sensor from my 1997 Jetta. It is thoroughly frozen in place and now the 22mm nut is stripped. Any suggestions?

Since you’re replacing the sensor anyway. take a propane torch and heat the nut up good and hot till it’s red. Then let it cool back down for about an hour. Take a ViceGrip or a pipe wrench and clamp onto the sensor to turn it out.


Good advice, but I don’t know if a home owner type propane torch will get it red hot. If they have an oxy-acetylene torch then they’ll be fine. Be careful with fuel lines and such though.

Some O2 sensors are hard to get to as well, complicating matters considerably.
Have you tried PB Blaster or Kroil on it yet?

This should’ve been attempted while the exhaust pipe was hot, which allows for easier sensor removal. Trying it cold means the metal is contracted tight around the sensor, making it almost impossible to remove. The threads could get ripped out or, in your case, the hex nut gets rounded off.

If you don’t have a torch, drive the car some to heat up the exhaust, and grab the sensor real tight with a set of vise-grips or right-angle pliers and give it a good twist. It should come out.

Removing a hot sensor from a hot bung never works. The sensor threads are stainless steel, and the bung threads are carbon steel. And if both are hot when trying to unscrew these disimular metals, you’ll tear the threads out of the bung everytime because it’s softer material. I work in diesel emissions, and we use all kinds of sensors in the exhaust systems. And each time someone tries this. it’s, “Hey Tester, I messed the threads up in this bung! Can you weld on another one?”


Odd, it’s worked for me on quite a number of vehicles with no ill effects on the threads.

My understanding is that you HAVE to do it hot because the pipe squeezes things too tightly when cold.

You can certainly try cooking the thing with Propane or MAPP gas which burns hotter. Some hardware stores sell Oxygen-MAPP gas torches that you can use to get into real trouble as they can melt or burn iron/steel.

If you have good access to the sensor, you can use a Dremel or something similar to grind new flats onto the O2 sensor, then apply a BIG pipe wrench. With a little help from a three foot pipe slipped over the handle of the pipe wrench, something will give.

Conceptually, you can drill the O2 sensor out and retap the hole.

Or you could just apply propane heat, let it cool, apply a couple of doses of PB Blaster, attack it once with a pipe wrench and, if that fails, take it to someone with tools and experience.

The corners of the oxygen sensor nut are rounded? Did you use a 6 point or a 12 point tool? You should use a 6 point.
I removed a very stubborn, original, oxygen sensor from a 17 year old Honda, recently. It would not come out cold. I ran the engine a short while; then, I used a tool I made from a 6 point 7/8" oxygen sensor socket (with the slot). I ground six flats around the socket, where it fits around the nut, for a 1 1/8" (or, 28mm) box-end wrench. This would prevent the socket from spreading, and allow extra force to be used on that stubborn nut.
I put the 1 1/8" box-end wrench on the newly cut flats on the socket, and put that on the oxygen sensor. Foot-power, pushing the wrench, loosened, and removed the oxygen sensor. I used a thread chaser to clean up the threads for the new oxygen sensor.

I can understand using that slotted socket if you’re trying to save the old one.

Normally, I’m throwing the old one out so I just cut the wire(s) and slide an impact quality, deep well, 6pt socket over the old one and use a breaker bar.

I’ve seen too many backyard mechanics do damage using those slotted sockets to remove old sensors that I wish they would label them as an installation tool only. If you understand their limitations, as you obviously do, they can work OK but too few people know this and end up screwing things up with those sockets.

Now that it’s messed up, I’d recommend the OP get a can of B’Laster PB and a properly sized pipe wrench. They come in all sizes. Pick one that fits in the space allowed and find a length of pipe or conduit to slip over the handle and apply leverage. A properly adjusted pipe wrench has an advantage in that it gets tighter the harder you pull on it. Soak the threaded base of the sensor with the B’laster PB and let it sit for 15 minutes. Then soak it again and apply slow and steady force. It will come out.

Yes, a deep-well impact socket will work in certain conditions; but, in this instance, the 1/2" drive couldn’t be used. There was just no access,unless I drilled a 1" inch hole down through the intake manifold. I could only use a box-end wrench. The 7/8" one was flexing way too much and couldn’t apply the needed force to the nut. A larger wrench gives added strength, and allows greater force to be applied.
An impact socket has the wall thickness to allow six flats to be ground for use of a larger box-end wrench. I used the slotted socket because it was thick enough, and the box-end wrench around the socket would keep the slotted socket from spreading.