So my 2010 Prius recently got a code for the upstream O2 sensors heater circuit (P0031) and I tested the heating coil and the circuit is not complete so I ordered a new one. The old one obviously is pretty well stuck on there so I have been researching the best ways to get it off. One interesting way was using dot 3 brake inplace of penetrating oil. Has anyone used dot 3 brake fluid to get an O2 sensors off? Is it safe to use since it’s flamable? I have a lot of dot 3 sitting around so it would be great if I could use it. Thanks in advance and sorry if I missed this mentioned somewhere else. I saw it mentioned for removing normal screws and saying it was falamable, hence why I was curious if it was a good idea on an O2 sensor.

  • well, if it is flammable, don't do it with a hot exhaust.... – Solar Mike Jul 11 '18 at 19:52
  • If PB blaster (or other penetrating oil) doesn't do it, hit it with a torch. Heat up the "nut" end of the sensor, and get it moving before it completely cools. Don't try this if there's oil or anything else flammable nearby. – 3Dave Jul 11 '18 at 21:40
  • Also, are you using a wrench, or an O2 sensor socket? The latter is MUCH better when dealing with stuck sensors. If you're really curious, pour 1-2mm of DOT3 in a plastic cup that you don't like, and try and light it with a match. – 3Dave Jul 11 '18 at 21:59
  • @SolarMike - No more flammable than any other penetrant you might put on it ... more than likely less flammable ... Don't know, for sure though, lol. – Pᴀᴜʟsᴛᴇʀ2 Jul 11 '18 at 23:27
  • @Pᴀᴜʟsᴛᴇʀ2 we won’t be testing it will we :) – Solar Mike Jul 12 '18 at 3:09

So the new O2 sensor is placed in the vehicle...but I did not really get a good use of the solution I made up. There was this flange attached to the stock O2 that I shot the fluid into but the fluid barely made it on the other side of the flange and on the threads (see attached image). With out taking it off I thought this part was just part of the exhaust manifold shielding but I realized I was wrong once I took the O2 sensor out. Not enough fluid got on the threads to tell if it really works or not. I had the run the engine for about 1 minute to warm it up just enough to remove the sensor and with a cheater bar it came off. I can confirm it is safe to use on the exhaust and for O2 sensors (probably not good for a new one though) because my car has not caught on fire or had any harm done to it. Thanks for all the comments guys! And hopefully someone else can also confirm this solution mix of 50/50 dot 3 and acetone really works!!

On the old (dark discolored one) you can see that the threads are not glosses like the rest of the sensor because the fluid didn’t make it far onto the threads. This flange is where I shot the fluid but in reality I should have shot it behind the flange to get it on the threads.

  • What kind of socket did you use on the one you removed? I don't see any flats on it like a normal O2 – Moab Jul 13 '18 at 14:41
  • The socket has to fit in that annoying flange, inside it is has the normal head like the new one. I only found one socket to fit on it, it was the one adapter that goes over the entire sensor. I was able to use the loaner tools actually from advanced auto parts luckily so I did not have to buy any special tools. – user6383357 Jul 16 '18 at 15:33

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