I'm having trouble removing the downstream O2 sensor on bank 1, the passenger side, on my '18 3.5L EB.

The upstream one on that side was pretty tough, but a 3/8" ratchet with an extra foot or so of bar got it moving. Turned out the threads maybe 3 rounds back were messed up, so it took a decent amount of force.

But the downstream one has even less space, and seems to be stuck more. I sprayed a bit of WD40, and I didn't get the truck fully up to temp, but let it run for ~3 minutes. I tried a few options with 3/8" and 1/2" ratchets and some offset O2 sensor sockets from OReilys. I even used a swivel extension and a breaker bar down below, but it didn't quite have a full connection and slipped under lots of force. I tried removing the heat shield, but that didn't come out and didn't give me that much more room.

Do people somehow use an impact driver to get this out. I'd need to get a swivel extension that's rated for an impact driver, but have a couple battery powered ones and then a more powerful air one. There's also a funky curved O2 sensor wrench from Ford that Napa lists. I'm going to order the sensor, but if I can't get it free I might end up just paying someone to install it, or at least break the old one free.

(EDIT: Looks like for $20 I can get a set of impact rated swivel joints, and a set of 1/2" extensions, from HF. That would probably be enough to get it around the cat and from under the truck, either with a breaker bar or one of my impact drivers. The older Ridgid and Makita ones probably aren't powerful enough, but I'd start there. They also have ratchets with a swivel head, but so far the ratchets I have are too big to fit on the underside of the O2 Sensor offset ratchet, but an extension can get it there, and a swivel adapter should be fine as long as it swivels enough to get an extension around the cat.)

Any tricks or tips would be great. Thanks

 

I normally have used penetrating oil, and manual tools. 6 point socket. WD40 is not really a substitute for PB Blaster, or other quality penetrant. Controlling a flex socket, or extension is allways a challenge with impact. Breaker bar and 6 point socket would be best. There are videos of O2 sensor removal. Probably one on the F150.

Edit:
Just saw this after posting. Pretty nifty idea. I have the same socket I have used for years. Those sockets do have a certain amount of flex. This clamp idea is one I will remember for the future.

 

I'm not seeing your video, and don't see it when quoting. Maybe you forgot to paste it in?

I have a bunch of other penetrating oils like Liquid Wrench, Triflow, and Bolt-off. I'll give that a try too...just harder to get in to the sensor threads.

 

I typically use PB Blaster for stubborn threads. I recently saw a video where a mechanic used crayons on a hot threaded joint, and it worked. The crayon wicked into the joint. He melted a lot more of the crayon than I thought was necessary, but maybe that's why it worked.

 

I've sacraficed more than one box end wrench to the torch and hammer to make something "custom fit". You can also cut one end off so a pipe will fit on it for more leverage. We've had to do that for some stuff at work. Actually two drawers on one of my toolboxes at home is labeled "good wrenches" and "cheap wrenches" so I know which to grab when I need to abuse one ha ha.

 

PB Blaster is some amazing stuff.
I have taken off rusted bolts on a boat trailer that I thought I was going to have to grind off with that stuff.
If your not in a hurry, just spray the threads every day for a couple of days, The thermal expansion and contraction along with PB Blaster
should get it freed up.

 

When I pulled mine off, I had to back and forth it, wiggle it. Just trying to loosen wouldn't work.

 

A 50/50 mix of acetone and ATF works well and is less expensive that PB Blaster

 

Nice, I'll have to keep that in mind.

I put some Liquid Wrench on it before leaving for the weekend, and will put it on a couple more times before the new part arrives late this week. I also swung by HF and picked up a flexible extension ratchet, and the swivel and extension impact parts. Something will work, especially with some penetrating oil and run cycles.

 

Tried a bunch of stuff. Including an air impact wrench that I had, and a electric one from harbor freight, though with some extensions I was running it backwards, so instead of the electric's "1050 ft lbs bolt breakaway" listed on the box, it's probably the 300 ft lb listed in the manual. And with a wobbly extension, of various types, I'm sure it takes a chunk off of that. I put a big torque wrench on it, and it said I hit 133 ft lbs, but that was one-armed while trying to keep the adapter seated well on the sensor. But no luck, even after using liquid wrench and PB Blaster, and having it warmed up some.

(EDIT: Also tried a flare wrench plus an extension. Maybe that worked better than I thought, and I could have used some of the ratchet adapters I never use to bring the torque wrench from 1/2" up to 1", for the other end of the flare wrench. Most of the O2 sensor adapters were offset and had a tiny bit of wiggle, which then offsets the force a bit and tries to come off the contact, and mess up the corners of the "bolt head" in the process)

So I tried 2 of the shops in our small mountain town. The first looked up the details on the computer which said they could do a replacement in .5 hours, so $80, later today. The second had a sign saying they wouldn't install user parts, but then he said they could give it a try, not mentioning money. He started in with a tiny 3/8" ratchet like I hadn't tried anything, but moved up to a box wrench, asking if he could clip the wires off the bad sensor. No luck, so he was searching for a big pipe that could fit. But then one of his guys got it to budge.

He said it would be tough, and the threading was messed up, but it was easy from there. I unthreaded it a turn, put it back in, and then out again just to double check. But it was fine. I put in the new one, plugged it in, and it worked.

All that, and he said there was no cost, just remember them in the future. I thanked him, and then just like when the tree guys drop off a free load of firewood, I made a batch of chocolate chip cookies for them.

I drove it up and down the mountain with forscan running. It seemed to be ok, but the cat will need to run a bit to be fully checked out. Hopefully all things are good. But at least the downstream O2 sensor is working now.

This shop didn't try anything really different, though a full box wrench gave it better contact, whereas the O2 adapters were offset and tended to ride up a little. Maybe a normal (instead of offset) O2 adapter would be better, with a hinged ratchet on it. But if the sensor is shot, then clipping the cables and fitting a full box wrench over it has the best contact, and then just put a big extension on it if needed.