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Old 05-13-2006, 01:14 PM   #1
GTWagon_Phreak
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97 LegacyGT Wagon 4EAT

Default O2 Sensor Removal Troubles

So I set about changing my O2 sensor today and unbeknownst to me the large hurdle would be the exhaust, not the sensor itself.

So after PB Blaster soaking and grueling wrenching, I got the heatshield off (I'm assuming this covers cat #1 or is that another muffler or what?). Of course the top part of the heatshield will not just slide off and from what I can tell, I MUST have the heatshield off to get my open-ended wrench around the O2 sensor. I can't see a way to fit an O2 sensor socket in there either.

How do you all get the O2 sensor out without dropping that part of the exhaust? I would like to get this thing out today as I'm driving a lot tomorrow, but it'll probly just have to wait until next weekend.

TIA!

EDIT

Final update:

Quote:
Originally Posted by GTWagon_Phreak
SUCCESS!! I finally got this beast beat. After over two weeks of workin' on it (maybe 3 actually), I finally got the O2 sensor out. For future searching reference, he is what did and did not work for me:

Did Not Work
*Trying to remove from engine bay - this was actually a possibility, as I was able to get a flare wrench around the O2 sensor. But despite hitting with PB Blaster previously and heating the exhaust up a bit, I was unable to get the sensor out.

*Removing exhaust heat shields - the manual says to do this, but I could not get to the sensor mainly because the top heat shield was still in the way also & you can't get it off without lowering the exhaust. Also even had I been able to get to the sensor, I think you'd need a particular tool to reach it. My 22mm open-ended wrench wouldn't have fit.

*Dropping cat-pipe only - This didn't work simply because the manifold to cat bolts were hard to get to and extremely stuck; as were the cat to mid-pipe bolts. If you have air tools this should be a cinch and might make things easier.

*Dropping headers only
- My headers dropped rather easily, probably because they were dropped @ the dealer for other service, but this did not open up enough room to get to the sensor. It needed to go a bit lower, hence my final solution.

DID Work
*Dropping headers & un-hooking mid-pipe - This finally gave me the access I needed. The mid-pipe hanger was easy to unscrew, a single 14mm bolt. Keep your 14mm socket handy, I used a 1/2" ratchet for a bit better leverage on it over the 3/8". The 14mm nuts on the header came of pretty easily and the gaskets probably could have been re-used, but I replaced them with some ordered from subarugenuineparts.com.
The 14mm bolt came off the hanger easily as well. From there the exhaust was lowered enough to get to the sensor and partially supported by the driver's side exhaust manifold which was hanging on some part of the
engine bay. I pulled out the offset O2 sensor socket I borrowed from a friend and it came out rather easily at that point; it was all a matter of leverage.

I think most people looking to do this the first time should just go the route I did. The exhaust manifold shouldn't be torqued down very hard, so it should be easy to remove. Just buy/borrow an O2 socket (22mm) for easy access to the forward sensor. I didn't even have to heat the exhaust up to get the sensor out, however I highly recommend investing in a can of PB Blaster. If the manifold nuts are stuck, you can hit them with PB Blaster the night before and it should help loosen them up.

With 206K miles (assuming original manifold gaskets), the gaskets looked in decent enough condition to be re-used. Rather than chance it, I ordered two from subarugenuineparts.com for like $6 each or something. I also ordered the cat-pipe gaskets in case I needed them, but those are just extra now.

Those looking for a good price on an OE O2 sensor, I recommend checking out http://www.car-stuff.com. I got the front one for like $60-something shipped. The rear O2 sensor I got for $30 from eBay (OE also), but I ended up not switching it now because it was also being a bitch and I didn't feel like dealing with it today. Dropping the rear part of the exhaust should be easy enough I can get to it better at a later time should I need it.
If anyone wants a rear OE Bosch O2 sensor for $35+ship, lemme know!

Hope this helps anyone searching in the future, it was quite the adventure

EDIT I forgot my victory picture
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Last edited by GTWagon_Phreak; 05-29-2006 at 08:03 PM.
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Old 05-13-2006, 04:47 PM   #2
NiTRoN
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which O2 sensor ur replacing?.. my car has 2 of em.. one right before 1st Cat (yea I got 2 cats..) and 1 past the 2nd cat.. Either of em were easy enough to replace.. just make sure you unplug the cable from socket, otherwise that will give you hard time while unscrewing it. and if you have to lower the exahust.. unscrew the 3 botls on each side from engine block that hold the pipe and drop the whole thing few inches down.. its allot easier that way than taking whole exhaust apart.. I wouldn't recomend dropping it from rear and leave the front on, it might crack flages or even pipe.. Therefore drop front and let the back swing on the rubber hangers.. Use some kind support so it doesn't drop totally down, that should give you enough clerance to stick your wrench in and remove it.
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Old 05-13-2006, 05:58 PM   #3
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Its the front one alright. I took a pic of it for clarity:
http://www4.ncsu.edu/~tjsupple/exhaust.jpg
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Old 05-13-2006, 07:45 PM   #4
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I was able to put wrench from the inside engine bay (but its tight).. after removing airbox.. but like i said.. i'm on MY00 model.. not sure what is in the way of your on 97 models.. If you still can't get in, drop the front exhaust few inches.. u might also have to undo the mount under tranny that supports middle section..
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Old 05-13-2006, 08:26 PM   #5
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it's easy if you drop the cat pipe instead of working with it attatched.
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Old 05-13-2006, 09:01 PM   #6
GTWagon_Phreak
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Quote:
Originally Posted by Wiscon_Mark
it's easy if you drop the cat pipe instead of working with it attatched.
Are you saying detach the headers themselves or the individual pipe where the
O2 sensor is?
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Old 05-13-2006, 09:55 PM   #7
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well, there's a flange on either end of the two cats, one to mate with the headers, one to mate with the midpipe, you can just drop the cats, and that will reveal both o2 sensors. Spray some PBBlaster on those suckers, and that should ease your job greatly.
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Old 05-13-2006, 10:07 PM   #8
GTWagon_Phreak
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I should be able to do that easily enough. There aren't any gaskets or anything in there I'd have to replace in the process is there?

Any other tips to dropping the cats?
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Old 05-13-2006, 10:10 PM   #9
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you could replace them, I guess, but I don't think you have to.

Oh, watch out for the donut gasket, it's a tricky one (between the cat and the midpipe, I belive).
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Old 05-14-2006, 09:19 PM   #10
NiTRoN
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With a stock headers I had pita of undoing the flages bolts before cats.. tight sqeeze on 1 bolt between the front differential on that bend, but its duable too.. for me was just easier to undo 6 headers bolts and lower the sucker..
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Old 05-14-2006, 10:32 PM   #11
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Quote:
Originally Posted by NiTRoN
With a stock headers I had pita of undoing the flages bolts before cats.. tight sqeeze on 1 bolt between the front differential on that bend, but its duable too.. for me was just easier to undo 6 headers bolts and lower the sucker..
That front flange is at a tricky spot.

When removing the cat pipe last week from an '01, those bolts were completely rusted. We ended up removing the exhaust manifold and the cat pipe as one piece and cutting the bolts off.

As for the sensor, we just unhooked the electrical connector and dropped it with the pipes. Much easier, IMHO.
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Old 05-14-2006, 10:39 PM   #12
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So the concensus is to drop the headers from the block and just get at it that way huh?

Will it hurt anything if I run the engine a little with the headers off? Boxer rumble FTW
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Old 05-14-2006, 11:03 PM   #13
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Also, for re-attaching the exhaust, should I use a torque wrench or just tighten the bitch as much as possible?
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Old 05-15-2006, 12:13 AM   #14
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Torque wrench is suggested, but difficult to get in there.

Be careful if you don't use one, because if you tighten it too much you can easily strip the holes out of the heads. This may not be an issue, but we had one of the studs come out instead of the nut.
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Old 05-15-2006, 03:22 AM   #15
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Quote:
Originally Posted by GTWagon_Phreak
So the concensus is to drop the headers from the block and just get at it that way huh?

Will it hurt anything if I run the engine a little with the headers off? Boxer rumble FTW
You'll sound like an old VW bug. And yes, I do know this for a fact.
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Old 05-15-2006, 08:52 AM   #16
GTWagon_Phreak
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Quote:
Originally Posted by IronMonkeyL255
Torque wrench is suggested, but difficult to get in there.

Be careful if you don't use one, because if you tighten it too much you can easily strip the holes out of the heads. This may not be an issue, but we had one of the studs come out instead of the nut.
Yeah I think I'd rather use one than risk messing something up.

I think I'm going to get a 1/2" set of sockets, as I don't have any and I'd bet those will make my life a lot easier than trying to struggle with a 3/8" set.
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Old 05-15-2006, 11:20 AM   #17
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They may.

I usually end up using 3/8 for just about everything, though. I doubt you would need 1/2 unless you really want an excuse to go out and buy more tool (I need more of those excuses).
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Old 05-15-2006, 11:38 AM   #18
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Quote:
Originally Posted by IronMonkeyL255
They may.

I usually end up using 3/8 for just about everything, though. I doubt you would need 1/2 unless you really want an excuse to go out and buy more tool (I need more of those excuses).
Maybe I'll just get a good piece of tubing to go over my 3/8" wrench and torque those bitches off. The main reason I was thinking 1/2" is for the bigger wrench, easier to get those rusted old bolts off.

In case I break some bolts, am I going to have to go to the dealer for them?

How loud is it with headers off? Might wanna piss of my neighbors
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Old 05-16-2006, 09:29 AM   #19
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What O2 wrench are you using? Get the crow-foot type. there is not enough room for the socket type. I have an '02 and used the crow-foot, not easy but not hard.

I really have no idea on your year but the picture looked about the same.

Peace,

Greg
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Old 05-16-2006, 09:55 AM   #20
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Quote:
Originally Posted by b4wantab
What O2 wrench are you using? Get the crow-foot type. there is not enough room for the socket type. I have an '02 and used the crow-foot, not easy but not hard.

I really have no idea on your year but the picture looked about the same.

Peace,

Greg
The year is listed under Vehicle to the left

I went out and got an open-ended 22mm wrench, is that what you mean by crow foot?
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Old 05-16-2006, 10:00 AM   #21
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Step 1: unplug the o2 sensor form the harness under the hood
step 2: Unscrew the bracket holding the cable to the engine block
step 3: Cut cable off the bracket (not the cable itself, just the plastic fasteners)
step 4: Put end of wire through the o part of a huge wrench ( forget the size)
step 5: slide the wrench down the wire until it's on the sensor
step 6: put wrench on sensor and pull like hell

or alternative directions

step 1: go to autozone and rent an 02 sensor removal tool (free)
step 2: put tool on sensor
step 3: pull
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Old 05-16-2006, 10:53 AM   #22
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Quote:
Originally Posted by Sausage
Step 1: unplug the o2 sensor form the harness under the hood
step 2: Unscrew the bracket holding the cable to the engine block
step 3: Cut cable off the bracket (not the cable itself, just the plastic fasteners)
step 4: Put end of wire through the o part of a huge wrench ( forget the size)
step 5: slide the wrench down the wire until it's on the sensor
step 6: put wrench on sensor and pull like hell

or alternative directions

step 1: go to autozone and rent an 02 sensor removal tool (free)
step 2: put tool on sensor
step 3: pull
You're suggesting that you can get to it through the engine bay??
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Old 05-16-2006, 06:34 PM   #23
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Quote:
Originally Posted by Sausage
Step 1: unplug the o2 sensor form the harness under the hood
step 2: Unscrew the bracket holding the cable to the engine block
step 3: Cut cable off the bracket (not the cable itself, just the plastic fasteners)
step 4: Put end of wire through the o part of a huge wrench ( forget the size)
step 5: slide the wrench down the wire until it's on the sensor
step 6: put wrench on sensor and pull like hell

or alternative directions

step 1: go to autozone and rent an 02 sensor removal tool (free)
step 2: put tool on sensor
step 3: pull
Are you sure? The WRX has cats in the DP, the legacy does not.
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Old 05-16-2006, 09:53 PM   #24
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As for headers reinstalling after you drop, keep the gaskets and retourqe them to 25flbs, u migh need extention but shouldn't be that big deal with small torque wrench.. If you decide to go with new gaskets cause old one are craped out, get em from dealer for about $10 per pair.
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Old 05-17-2006, 08:39 AM   #25
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Default Crow Foot

I figured the year was late 90s but when I was responding couldn't check and didn't remember. So you got me.

A crow foot looks like a line wrench with it's end cut off. Or like a box end wrench with a slot for the O2 cable. It will be about 3-4 inches long. one side will be the box end/line wrech side the other side will taper to a small handle/shaft. The handle/shaft area will have a through hole for a 3/8" dirve.
The whole thing is about an inch or so thick. One side is extended to get below the level of heat shields and such. Because of the 3/8" drive in the shaft you can get all different angles.

I picked one up at Pep Boys. They had no idea what I was talking about but they had them on the rack in the isle.

I jacked up the pass front and did it all in 30 minutes without rushing.

Peace,

Greg
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