How do I remove this oxygen sensor?

[sgtBerbatov]

Part of the work I'm doing at the moment requires me to take the front pipe of the engine off. I've done that, and I've also decided to replace the oxygen sensor as it's nearly as old as the car itself.

Thing is, I've taken it off and well there doesn't seem to be any proper nut left? It's either welded on or over time the nuts have just "melted" on to the stud. I've attached a photo of the offending item.



How on Earth do I get this off? Can I even get it off? Or will removing it be that catastrophic to the front pipe that I might as well purchase a new pipe anyway

[GreenV8S]

Those two lumps to either side of the sensor look like studs welded to the exhaust with the heavily corroded remains of nuts on them. Judging by the pictures I don't see any hope of them unscrewing and I expect you will need to cut them off and then weld on new studs. Whether there's enough sound metal left on that boss to let you do that remains to be seen - you might end up with quite a big repair there. Is it worth that work to replace a sensor that seems to be working OK?

[E-bmw]

Actually, looking closely, it seems that the studs may be Ok but the nuts are toast.

I would be VERY CAREFULLY hack sawing the remaining nuts until they fall off, re-cutting the thread on the studs and you should be good to go.

[sgtBerbatov]

The car suffers from emissions, has done for the last two or three tests. I'm doing other work to it so thought for the sake of a £40 sensor I might as well change it.

I'm going to clean the rust up first with rust remover spray and give it a clean with a wire brush. Then try and fit a socket on it or cut it. They're that badly gone there can't be a whole lot left of them on the thread!

[Mignon]

I beg to differ but it's very unlikely those studs are welded into the flange. They'll just be normal screw in studs. Clean the nuts up with a wire brush and then hammer on the smallest socket that will fit. Then try mole grips. If that doesn't work then weld a bigger nut, a 10mm one ideally, to the old studs and nuts and then unscrew the lot. Replace both studs and nuts or just use bolts.

[227bhp]

Heat and lots of it.

[Liamsaid]

I had the same thing with my mr2, only I wasn't taking the pipe off and couldn't get a blow torch at the nuts. I was geared up for a fight but they came off easily. A squirt of plus gas left for an hour, then I used an Irwin bolt grip on the end of around 9 inches of extension bars to my impact gun.

Irwin bolt grips and plus gas are well worth having in the toolkit when working on older cars.

As you have full access, get a blow torch on them, then try undoing them while still hot.

Edited by Liamsaid on Thursday 3rd August 18:14

Edited by Liamsaid on Thursday 3rd August 18:50

[imagineifyeswill]

As a self employed mechanic I deal with these kind of problems daily, Ive found that these flanged nuts on exhaust components split very easily if you use a good sharp chisel on the flange part of the nut.

[AdamIndy]

If you can get a nut splitter on there then that's what I would use. Failing that I would knock it loose with a hammer and chisel.

[crankedup]

AdamIndy said:

If you can get a nut splitter on there then that's what I would use. Failing that I would knock it loose with a hammer and chisel.

Agreed, buy a nut splitter and that tool will make the job of removing those nuts a doddle.

[Adam32]

Get some heat on there and spray with oil. You may have to do it a few times. Then I use some Knipex Cobra. They are the best purchase I ever made and get me out of trouble all the time.


https://www.amazon.co.uk/Knipex-00-20-V02-Multi-Co...

[MrBodgefix]

Heat. lots of it! Then an Irwin bolt grip or the smallest socket you can get over it may do the trick. Looks like one of those jobs were it might be easier to just buy a new downpipe However the old saying if it aint broke don't fix it comes to mind!

[CarsOrBikes]

The studs look in decent order, as above, heat and a small socket or sharp grips