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Discussion Starter · #1 ·
OK…so, let’s say you have a bolt you expect to be a pain in the butt to remove — specifically a downstream O2 sensor.

Is there any reason to use penetrating fluid on a bolt when you find it just as efficient to heat it to extract it?

If it is just as easy to heat it, why waste the time and money spraying it with penetrating oil? 🤷‍♂️
 

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2018 Ford Focus ST1 with a 2867 gen 2
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I've had some bolts which heat alone worked, some which penetrant like pb blaster worked, and some which needed both. The last time I removed the O2 sensors from a downpipe, I had to use both to break them loose.
 

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OK…so, let’s say you have a bolt you expect to be a pain in the butt to remove — specifically a downstream O2 sensor.

Is there any reason to use penetrating fluid on a bolt when you find it just as efficient to heat it to extract it?

If it is just as easy to heat it, why waste the time and money spraying it with penetrating oil? 🤷‍♂️
Also don't rule out my favorite for the REAL stubborn stuff...
Get one side red hot (either the bolt, or whatever it screws into, (not both if you can help it) with a torch, then pour ice water on it. Obviously not an operation for cast materials, but the temp shock and differential will do wonders to break the corrosion bond. Your goal is to shrink one or the other real fast while the other doesn't. The larger the diff in temperature between the two, the better.
Other than that, heat and/or an impact are always my go-to. Another one is getting evil on the bolt head with an air hammer loaded with a blunt end with the idea of just trying to break the bond down in the threads. I've had to use that quite often on tractors with larger bolt heads.
Of course on a O2 sensor, the options are limited... but the heat should do it. Just use map gas so it actually gets hot. Propane isn't anywhere near as good
 

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Discussion Starter · #5 ·
Thanks Guys!! I’ve got a Bolt Buster I’m planning to use if the O2 sensor has an attitude. I’ve used it on 2-3 dozen stubborn bolts. Thus far, it’s batting 1.000!!

@rob99rt The bad downstream O2 sensor is on my wife’s minivan. I’ll spray it a couple times per day for a few days with Liquid Wrench before I tackle it. 👍
 

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Thanks Guys!! I’ve got a Bolt Buster I’m planning to use if the O2 sensor has an attitude. I’ve used it on 2-3 dozen stubborn bolts. Thus far, it’s batting 1.000!!

@rob99rt The bad downstream O2 sensor is on my wife’s minivan. I’ll spray it a couple times per day for a few days with Liquid Wrench before I tackle it. 👍
My vote, for what it's worth, if definitely the PB blaster. Soak it for a couple of days before hand. If it doesn't want to loosen up try tightening it up just a bit to shock the threads the try to loosening it.

Wear eye pro & watch those knuckles!
 

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There's no replacement for the blue wrench.

Stubborn O2 bungs usually have to be nearly white hot before they pop. It's a job for oxy acetylene.

I've commonly had the thread totally gall and leave material in the bung. Enough so that I have a 18mmx1.5 tap and an 18mmx1.5 low profile thread chaser. The sensor is always made of softer material than the bung is so the sensor threads get left in the bung.
 

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I took out my upstream O2 sensor a couple weeks ago by driving the car for a bit to warm up the exhaust, hitting it with PB blaster and letting it soak while I disassembled the engine bay to gain access. Then I attached my extensions and 18" breaker bar and had the thing out with little trouble. 98k miles on the car and original sensor.
 

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We haven't come across a stubborn exhaust bolt or O2 in awhile. There's a couple induction heaters I've kept my eye on. Some you can fit into tight spaces, where you can't as easily direct a torch flame. But they are expensive. I'd like to eventually get one for the shop... when the time comes.
 

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Discussion Starter · #10 ·
My faulty O2 sensor is on my minivan, not my ST.

That said, while researching how to replace it, it seems standard-operating-procedure to replace them at 100K?? If that's the case, I've got a total of 10-12 to replace sooner rather than later. :oops:
 
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My faulty O2 sensor is on my minivan, not my ST.

That said, while researching how to replace it, it seems standard-operating-procedure to replace them at 100K?? If that's the case, I've got a total of 10-12 to replace sooner rather than later. :oops:
I mean, it's probably a good idea if you're already working on them or in that area...but I wouldn't go out of my way to replace an O2 sensor unless it was failing/failed.
 
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