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Discussion Starter #1
Im replacing the O2 sensor on my 86 Spider and can't seem to figure how to get the old one off. There's a housing (looks like a bell) over the old one which I took off but I can't see any flats on the old one to get a wrench on. The manual says to unscrew it but nowhere to put a wrench and vice grips will crush it. Ideas??
 

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Discussion Starter #3
Thanks Tiger. Yep, thats the one. I guess the flats are down in the flange and I didn't see them. I was comparing the old sensor to the new one which looks different. Do you know what size socket fits the old sensor?
Thanks again
Joe
 

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if you are going to change it for a new one.. just cut the wires at the sensor..put the new one on with a flat wrench.. that's how i do it..i think it is a 7/8" or 22 mm..you can use a scoket to remove it if you cut the wires..
 

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It is a 22MM- I did it from beneath the car in 89- I was a lot skinnier then- If I had to do it over, I would get a 22 MM socket, wi extensions uni joint etc and do it from above- if you go from under, make sure you have some offset
 

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That "bell" housing makes this job a b!cz! I ended up completely removing the cat assembly to get enough room/torque on the subject. After I looking inside the rear end (of the cat converter), seems that mine was a molten lump of junk and replacement of the O2 sensor was pointless--at least in that cat. If your cat's monolith is sound, use a Dremel to cut that confounded bell off so that a "proper" pair of vise grips can solve the issue. (Along with heat & PB Blaster--but not simultaneous:cool:)
Funny that aftermarket OEM cats don't have that bell.
 

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Yes, the old one can be removed with a regular socket (as long as the wires are cut) but you cannot do that with the new one. When I did mine in April, I used a socket designed specifically for the O2 sensor. The attached picture shows something similar to what I got at Sears. I purchased a universal sensor (genuine Bosch) for $25 or so and replaced my old one. The replacement was identical to the old one except for the lack of electrical connectors.

P.S. I did not know about the "bell housing" on the stock S3 cat. It was a very, very straightforward job on my '91 S4.

Good luck,
 

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Discussion Starter #11
Thanks guys. You saved me a ton of headache. I wasn't going to change the sensor but when I was doing some other work I saw that one of the wires was melted off. Don't know why/how it happened but I'm thinking it may be why Im missing some of the performance.
Joe
 

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P.S. I did not know about the "bell housing" on the stock S3 cat. It was a very, very straightforward job on my '91 S4.
S4 O2 sensor points side way and that makes it a lot easier to replace than the S3 sensor which points upward and slant towards the front. Yes, there's also a crown (bell housing) at the base so one cannot use a wrench and has to use a socket.

The autozone type O2 sensor sockets are quite useless. I went through a few of them. One cracked and the others simply won't work if the O2 sensor is anywhere near a little tight. The split in the socket weaken it and the side wall would expand and slip on the nut. The sears socket has reinforced material at the bottom and looks stronger, but the question is whether it sits all the way down on the O2 sensor with the "protective" crown there. I think it probably should.

Anyway, you can give it a try but be warned that it is often not an easy job. Especially when you said a wire is melt. If there's any sign that the cat has overheated (running too rich), the O2 could have suffered high heat that could "fused" the sensor to the exhaust. Does the O2 sensor look original , old and/or rusty? If any of these, prepare for a battle!

Try to soak the base of the O2 sensor for a couple days with PB Blaster. Stuff a small piece of paper towel or cloth there to keep the area wet. Try not to damage the hex nut on the O2 sensor when you take it off. If the O2 sensor socket slips due to the flat area on the nut is rounded, I think it will be easier if you take the cat and downpipe down to work on it outside the car. I changed the O2 on two S3, one of them 2 years ago on a '87 and another one a week ago on a '86. Both sensors were likely original and badly fused to the exhaust. I had to take the exhaust down in both cases. To get better access, I first cut the crown out using a grinder with a cutting disc (a reciprocal saw was used for the '87) . For the '86, I also destroyed the top side of the O2 sensor so I can use a shorter 22mm socket on it. I heated the area up with a MAPP gas torch (acetylene is better, propane is not as hot) to cherry red before I try to loose the sensors. When the flat area on the nut start to round, I switch to a small pipe wrench and a 4' pipe for leverage. I was able to get the sensor off the '87 this way, but not the '86 a week ago. I ended up drilling, cutting with an air saw (across the thread) and chiseling out the remains of the old O2 sensor in small pieces.

So, you might want to take a closer look and give it a try (it might come out pretty easily in some situations). But if it does not budge, then it might be easier to go to (take the pipe down if you want) a muffler shop or machine shop and have some help taking the old one out.

Good luck,
Bob
 

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One cracked and the others simply won't work if the O2 sensor is anywhere near a little tight. The split in the socket weaken it and the side wall would expand and slip on the nut.

Whip a hose clamp around it after slipping the wire into the slot.

Still, I've yet to use the 'proper tool' on any one I've pulled or installed.

If a crecent, open end, or line wrench won't bring the old one out, a pipe wrench sure will.

They don't need to be brutally torqued back in place, so I've never gone beyond a wrench to install. :shrug:


I'm not saying that using the 49.99 proper tool is wrong, just that it's likely a bit un-neccisary, particularly when you see 3/4's of the exhaust shop guys get up in there with channel locks or vice grips to remove and install when working in that area of the pipes, (after you worked so hard to get and use the proper tool), and of the remaining 1/4, only about 1/3 of them of those have the actual tool, (but don't use it), while the rest use regular wrenches.

As in I've never yet seen an exhaust shop use the specific socket.
 

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Whip a hose clamp around it after slipping the wire into the slot.

Still, I've yet to use the 'proper tool' on any one I've pulled or installed.

If a crecent, open end, or line wrench won't bring the old one out, a pipe wrench sure will.

They don't need to be brutally torqued back in place, so I've never gone beyond a wrench to install. :shrug:


I'm not saying that using the 49.99 proper tool is wrong, just that it's likely a bit un-neccisary, particularly when you see 3/4's of the exhaust shop guys get up in there with channel locks or vice grips to remove and install when working in that area of the pipes, (after you worked so hard to get and use the proper tool), and of the remaining 1/4, only about 1/3 of them of those have the actual tool, (but don't use it), while the rest use regular wrenches.

As in I've never yet seen an exhaust shop use the specific socket.
cmon 49.99? look @ my post, $15 for whole set...
 

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I use my impact wrench socket (because it's longer than my "normal" sockets), and thread the wire through the hole at the top of the socket. Then grab the socket with vice grips and tighten. Like Tifosi says, you dont really need to wail on it when tightening, and just cut the wire and use a deep socket to get the old one out.
 

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cmon 49.99? look @ my post, $15 for whole set...
Yes, the $15 ones look good and I had bought a few :) ... but from my experience they are not that good :mad: ... the sears one does look better ... for some tools if you're going to buy them ... it pays to pay a little more and get a good one :)!

Hose clamp and impact wrench? Yes, I have tried those too :)! Once it is rounded, the best option is to grab it with a pipe wrench and use 4' extension for leverage! Exhaust shop usually just heat the sensor up to cherry red with an acetylene torch and use a wrench or vise grip to get it off. They do have more practice ...!

The question is whether you enjoy spending a couple (or a few) hours (if the sensor is giving you a hard time) trying to get the sensor off or spend a few bucks to let the "pros" do it :)? I have changed a few O2's, but the two S3 spiders that I worked on gave me some real challenges!

Below is a picture of the '86 spider O2 sensor with the top chop off. Didn't take any picture when I finally cut it up!
 

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dang, you are lucky that your car did not burned down totally...
 

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Discussion Starter #20
Ok...I just spent the last 3 hours with the AutoZone set, a bottle of PB and a breaker bar. All I did was round off the flats (and bust my knuckles). It's soaking in PB right now. The hose clamp idea is brilliant. I wish I read this post again before I went in the garage. I know it's worth it to have the"pros" take it off but I hate the idea of this getting the best of me. I was considering taking the cat off but the flange bolts look seized. One of these days I might actually get to drive it!
 
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