Was pulling P0420 before and after I wrecked my 4runner and just got around to ordering new Denso O2s. Problem is, I can't seem to get the bolts off. I tried wd40 but even with those the bolts wouldn't nudge. Granted I was using a normal wrench instead of a socket wrench because of how little room there is. Was working on one but it started to strip so I decided to call it off until I know how to get them off.

Does anyone have any tips to getting these bolts off? They're more stubborn than I thought.

Heat get the nut to glow then soak it with WD-40 or other penetrating oils.

The last one i did. I pulled the cat pipe off the header so I could get it off with good tools then put new nuts gaskets on all the above.

There isn't a lot of room to work in there so you might have to do that route like I did.

Heat

good to know, good thing I have a heat gun, I'll have to try that next. Do you spray the WD on immediately as it's turning red or wait then spray?

You have to watch WD 40 is flammable. Keep heat and flame away. So you heat up then spray when you pull the heat of flame away.

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I soaked mine for about a week with PB Blaster (gave them a good spray after every trip), used a bunch of heat AND a bolt/nut extractor tool to get mine off. And even then they still put up a little bit of a fight
I'd recommend getting some new bolts ahead of time just in case, though I can't help you out on what thread pitch they are. I just happened to have some already that fit

Agree with all the above, but also use a flare nut wrench (line wrenches) to prevent any further rounding off of the nut. You can buy a cheap set from Harbor Freight. I absolutely love mine and that was definitely money well spent.


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Thanks! I'll have to go get a can of PB sometime this week, the heat+wd didn't work at all so that'll be my next step.

Use the exhaust as the heat source. PB blaster. Soak it drive it around a day.. soak it again.

Then if it still won't come. I hate to see you have to cat pipe off the ar the header and the muffler pipe. As that can make the job alot longer and harder.

Good call on the flare nut wrenches as I had those nuts even want to strip with them and resorting to pull the entire pipe out.

You need 3 new gaskets and new nuts if you go this route but it can go bad especially those 3 nuts on the header .

I go the removal of the cat pipe only as the last resort.

Granted pre 2000 have feder one cat or California 2 cats. After 2001 they are all 2 cats.



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Another thing lots of mechanics use here is map gas or acetylene to get these nuts glowing red. That heating and cooling helps break the rust bond and shrinks the metal slightly which helps when removing nuts and or bolts.

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Just echoing the rest of the group here, but heat and penetrating oil are your friends with this. Spraying them with penetrant after driving and the exhaust is hot. A heat gun isn’t going to do much. You really need something hotter like a propane or butane torch. I had to use a propane torch and penetrating oil to get mine loose and my rig isn’t rusty.

On a side note, the nuts themselves are a self clearing/cutting design that almost acts like a die as you remove it.

I didn't think you have as much of a Gaulding action in the non rust areas. Learn something new everyday.

The exhaust doesn't seem to care what environment it's in. Must be the constant heating and cooling that causes it. Good to know..

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What all the other guys said and I'll add, get yourself some flex head ratchets. I suggest getting some from Gear Wrench that have 120 engagement points. This means you only have to turn the ratchet 3 degrees to get to the next ratchet engagement which is crucial when working in tight areas.

If you didn't watch my video yet, maybe it will help you.





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First, it's not a bolt, unless a PO has done things to it. They are nuts on studs. The nuts are a whole lot softer than the studs, so sometimes the nuts have to come off in pieces. In the salt belt, this is pretty common. Fortunately, that is not that hard to achieve.

First, use all the techniques above at your choice. If, despite your best ministrations, you are still left with a rounded blob of stubborn rust, do not despair. Take a few cheap Chinese sockets and pound them on, in successively smaller sizes, and the nut will become progressively smaller. A pair of small Vise-Grips, tightened to the max and turned with a perpendicular rod or screw driver, in between the sockets will help. In most cases, the nut will eventually turn, sometimes when it is bare shreds on the stud. Or at least it will fall off in pieces.

Or, in extreme cases, cut the stud and nut, remove the flange, cut again, drill a hole, tap, and replace with a bolt. I only had to do this once. Mostly the nuts come off, leaving the studs in surprisingly good shape after a little stiff wire brushing.

Good luck!