Removing an oxygen sensor

chainsaw_masochist · 4 Jul 2020

I am trying to extract this oxygen sensor so that it can be used again in a replacement exhaust.

There are many examples on YouTube of folk doing this but just about in all cases, contrary to my objective, they are attempting to replace a new sensor into an existing exhaust. So far I have avoided cutting the section of pipe that holds the sensor away from the exhaust in order that I have something substantial to turn the wheelbrace against. You can see that I have tried to saw vertically into the sensor seating hoping that this would weaken the connection. I have a heat gun, a blow torch and ultimately an angle grinder but so far have been reluctant to use these for fear of damaging the sensor. Anyone been confronted with this type of problem before?

Any advice much appreciated.

Burnerman · 4 Jul 2020

For sure, these things can be ferociously tight, and those split spanners are a waste of time, 95% of the time.
You need to get the pipe in a vice, really.....you may have a ring spanner that would fit, if the electrical connections would pass through. I have a huge adjustable spanner that I call on here - it must be 14" long

.
Anyway.....consider grinding the housing away down one edge, until the sensor threads are just visible and then trying to unscrew. Once the housing has split, the sensor will unwind. By all means heat the housing directly from below the sensor if you think it would help.
If all else fails, the genuine sensors aren't so expensive but I wouldn't buy an aftermarket one.
John

Mottie · 4 Jul 2020

A big pair of stillsons with a scaffold bar should do the trick.

chainsaw_masochist · 4 Jul 2020

John: Yes, I obtained a stouter shorter sensor socket as I was told the longer type do open slightly when subjected to a lot of torque but actually that very thing is happening here, so it is trying to round the edges. The largest adjustable I have is 12" but even with a tubular basin spanner precariously over the end it doesn't really achieve much. Anyway I’ll dig out the grinder in the morning and give it some action as you describe. Same for the blowtorch. I seem to be getting prices of around £100 per sensor from the Toyota website (it's a 2002 Yaris). There are plenty on Ebay for £25 upwards but I am reluctant to purchase.

Mottie: Once again, my stillsons are a bit short in length terms and a small section of scaffolding is well worth keeping around the manor. I will try to obtain these next week if the above fails.

Thanks, gents.

chainsaw_masochist · 6 Jul 2020

Well with a combination of the 12" adjustables and with the basin spanner on the end plus some liberal use with the angle-grinder I managed to get them out. The exhaust sensor (the one below in photo) took about an hour and the one twixt manifold and catalyst a piffling 20 minutes. So thanks for your tips, guys.

Just a couple other things, the front sensor was fitted with a small seal and presumably I require a replacement to go back into the new exhaust? Perhaps I can just buff up the existing for this? Also the received wisdom appears to be that I need to use dielectric grease when reinstalling the sensors – Permatex seems to be a regular product. Any views?

Burnerman · 6 Jul 2020

Seal wise, I just use a copper washer if there's one missing......seriously you don't want any leaks.
I can't say I've ever heard of dielectric grease, I just use ceramic brake grease and it seems to be fine - but once in the sensors stay there

Well done for persevering with this - it does make you wonder just how they can be so tight! I've never had success with my split socket to remove them but I do use it to screw them back in.
John

leegsi · 7 Jul 2020

Its a crush washer.

If your worried about any leaks fit with a smear of silicon to seal it as silicon is heat resistant and wont be effected by the heat of the exhaust (we use silicon to fit exhaust where we work as the exhaust paste can crack and cause leaks)

chainsaw_masochist · 8 Jul 2020

Burnerman said:
Seal wise, I just use a copper washer if there's one missing......seriously you don't want any leaks.
I can't say I've ever heard of dielectric grease, I just use ceramic brake grease and it seems to be fine - but once in the sensors stay there
Well done for persevering with this - it does make you wonder just how they can be so tight! I've never had success with my split socket to remove them but I do use it to screw them back in.
John

Well given that there appears to be a week or so delay with getting stuff from the bay I ventured out yesterday to our (seemingly) one sole motor factor – Halfords. Absolutely buġġer all cbg, though be reassured, they have around 12 varieties of car wash soap and 28 different types of body polish. I will try somewhere else today.

leegsi said:
Its a crush washer.

If your worried about any leaks fit with a smear of silicon to seal it as silicon is heat resistant and wont be effected by the heat of the exhaust (we use silicon to fit exhaust where we work as the exhaust paste can crack and cause leaks)

Yes, so I understand. What is confusing, though, is that the sealing gaskets that go between each of the bolted unions of the replacement exhaust are also referred to as crush washers. It would be more meaningful if they were called doughnut gaskets etc. Maybe it’s just me?

The silicone is on the way through the post evidently. There appears to be about a week’s wait on all things ebay currently so I am sitting by the letterbox.

Just a couple more questions:
1) It is necessary to clean the sensors before being reinstalled? There exists of YT a slew of vids demonstrating the need to remove the existing carbon. Some just recommend soaking in petrol, others spraying with carburettor cleaner (also missing in Halfrauds

), one guy even uses water – soaking and spraying.
2) Also the sensors have a required torque setting – I think it is around 32lb/sqin (not so much, really). Using the split socket with its offset drive connection can an accurate tightness be achieved using a torque wrench? Something tells me that this setup defies achieving the correct torque?

chainsaw_masochist · 13 Jul 2020

Guys, I still have a couple of questions that I would like your advice on. The crush washers turned up today but they are quite different from the washer (seemingly captive as it does not unscrew from the thread).

1) There never was any washer on the sensor between the manifold and catalyst - should I put one of these on or just rely on the sealant?

2) The ceramic brake grease has yet to arrive but could I use Visbella gasket maker around the sensors instead? I was planning to run a thin ream around the provided gasket (made of wire mesh) but you may think this unwise in anycase.

3) It is necessary to clean the sensors before being reinstalled? There exists of YT a slew of vids demonstrating the need to remove the existing carbon. Some just recommend soaking in petrol, others spraying with carburettor cleaner, one guy even uses water – soaking and spraying.

Burnerman · 13 Jul 2020

The crush washer is probably now captive as it's diameter may have been reduced slightly when crushing.....I'm sure you could shift it by using some side cutting pliers or whatever just to weaken it enough to remove.
Any sealant won't harm a thing - I've never had a sensor leak anyway, and if you have a spare washer to go on the pre cat sensor then that won't do any harm either.
Cleaning wise, I lightly wire brush the threads and tip of the sensor, then flush clean with carb or brake cleaner to clear the crap away.
John

chainsaw_masochist · 14 Jul 2020

Very grateful for this advice, John, and will carry this out in due course.

Meanwhile I have had further problems with trying to separate the back-box section from the mid-section. I thought I could unscrew the bolts using wheel wrench etc but ended up sawing through the bolts.

Am I likely to be able to salvage this flange? I have a blowtorch which I have yet to use. If anyone feels inclined to say, "Why don't you just get a new back-box, you tight bxxxxxd?", then that is absolutely fine, it is just that it appeared to be in pretty good shape . Thanks.

Burnerman · 14 Jul 2020

That looks like the original manufacturer system, and yes that is a welded on nut - they are often that shape. Occasionally the manufacturers - in their infinite wisdom - use metric fine bolts too which are very difficult to replace

The flange could be salvaged, but only if it's off the car - you'll never get enough purchase on it otherwise. You can (picture 2) maybe hold the end of that stud firmly in the vice and try to unscrew it one way or the other - or drill the stud away. A bit of a faff, to be sure but new nuts and bolts with a flange gasket should sort it.
Good luck with it!
John

chainsaw_masochist · 4 Aug 2020

Yes, you’re quite right, John, it was the original Toyota exhaust as was, of course, the catalyst.

Anyway, the replacement Klarius catalyst/exhaust is now fitted (with the original sensors) but it is still not without probs. The car starts fine but the inevitable engine light remains on continually. There sounds to be a bit of a blow from somewhere in the system but the area around the flange (between the manifold and cat) is so bloody hot and compact that I cannot properly get my hand around the first flange to feel for any escaping gases. Also it smells as if it is running a bit rich and perhaps a little smoky from the rear box. It accelerates quite well and does not have problem holding speed but perhaps this too could point to being slightly rich.

This little motor which we have had from new has always run perfectly and has never had any issues at all with emissions re previous MOTs etc. It is difficult to conclude that there could be a sensor failure as these were just fine in the previous system.

At this stage the easiest thing for me to do would be to drive about 150 miles to my family home so as to get the car in the garage and lifted up on jacks and axle stands. But is this wise if it were running rich? Is it technically legal with an illuminated engine light? Also would this be likely to damage the new cat in anyway?

Additionally does anyone know if thes Klarius exhausts/cats are much cop?

Burnerman · 5 Aug 2020

Dammit we didn’t want to hear this

I’ve found Klarius systems to be well made and fit perfectly - although they don’t last anywhere near the same time as the original system.
Experience has taught me not to use pattern catalytic converters or sensors.....I’ve been bitten too often with these, especially with French vehicles.
Obviously there should be no fume from the engine, so you are over fuelling somehow.
You need to seal that leak unfortunately, then cancel the fault code and see if it reappears and go from there. I can’t see why the sensors have failed but maybe the fault code could give us a clue.
You still have the original cat on the car.....is that correct?
John

chainsaw_masochist · 5 Aug 2020

No, John, the damn thing was stolen a few weeks back – yes, that’s right they’re even the hitting 18 year Yaris/s now. I was completely bemused upon discovery but subsequent browsing of the interweb seems to show that the precious metals in the cat can exist in the earlier designs in sometimes greater quantity than the current items. The miscreants (not the word I used at the time) cut through the pipe either side of the two sensors. This is why I have been struggling to get this new exhaust fitted. You will also understand my reluctance to fit a pukka Toyota system. Not really sure where to go from here.

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Removing an oxygen sensor

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