Best way to replace O2 sensor?

[graphikg]

I am getting an O2 sensor reading and want to replace it, but I notice it is in a tight spot under the car. Whats the best way to replace it? I have an M50 525i wagon. I was thinking about just taking the headers off and having the exhaust just drop down, but is there a shortcut?

[racingwoody]

rent an o2 attachment for your socket wrench from your local parts store. Soak down your current o2 sensor with PB Blaster the day before you plan on switching it out. Should take all of 10 minutes to do. Don't drop the exhaust.

http://www.harborfreight.com/oxygen-sensor-and-diesel-injection-socket-set-99850.html

You want the inverted o2 socket wrench that look like the bottom 2 on the right. You can see they have a slit in them to put the wire through and you can use the socket from lying on your back. I just did mine this last week.

[AHenry014]

m50 cars are easy with the correct tool. o2 sensor socket FTW

[graphikg]

Didnt even know about this tool! Nice. Thanks guys. I am going to try it out.

[graphikg]

Got that set from HF and still wasnt ablel to replace it; much too tight up in there. I had no choice but to drop the exhaust which would have saved me time if I just started there. Its amazing how you guys can do it without dropping the exhaust, but i needed to with my wagon. Whatever, its done now.

[quick93]

Got that set from HF and still wasnt ablel to replace it; much too tight up in there. I had no choice but to drop the exhaust which would have saved me time if I just started there. Its amazing how you guys can do it without dropping the exhaust, but i needed to with my wagon. Whatever, its done now.
I ran into the same thing. I was doing the one for my neighbor who has a 95 525ia and couldn't get it. I did find the flex disc was falling apart though and he needed trans mounts so I didn't put a whole ton of effort into it since I was going to have to drop the exhaust anyway to do the other work. Oh, if anyone is in a pinch you can cut a slit down the side of a 7/8 deep socket to make your own o2 removal tool. I had to make one several years ago and its always worked great.

[Dexm]

Anyone uses a 22mm crows foot to remove/replace the 02 sensor? A crows foot I have, but not the 02 socket. If it'll work just as good, I'd like to know that going in. I've got a '91 535i by the way. Thanks for the replies.

[AHenry014]

I wouldn't. That suckers usually in there and grabbing two sides usually isn't enough. If all else fails, cut the wires off and use a real socket.

[Snailed525i]

Lol i just did almost this exact thing

[zubbie]

I wouldn't. That suckers usually in there and grabbing two sides usually isn't enough. If all else fails, cut the wires off and use a real socket.

this, deep socket works great. no need for a special tool to install

[jint45]

what are you guys smoking, takes 10 mins to replace an O2 on an E34. 22mm round wrench, cut the damn wires and put the wrench over and off you go, you throwing the sensor out anyway.

[Austin Charles]

10 min.?? mine took 3 days!!

Soaked it with PB blaster for two days, and at night. Needed a o2 wrench, which i had to add a hose clamp so it would stop striping. Then i had to use a 3/8 S flex ratchet and a 2' braker bar just to get square with the sensor. After a Black eye and three days it let loose.

Make sure you add anti-seize to the new o2 sensor.

[Jmac95E34]

what are you guys smoking, takes 10 mins to replace an O2 on an E34. 22mm round wrench, cut the damn wires and put the wrench over and off you go, you throwing the sensor out anyway.

More like what are YOU smoking?:confused
Try it on a '95 525 and then report back.
Not all E34s have the same engine/exhaust set up.

[Dexm]

Then i had to use a 3/8 S flex ratchet and a 2' braker bar just to get square with the sensor.

Yeah, that's my concern too. That's why I thought the ol' crows foot socket might do the trick with a u-joint. Don't have a flex ratchet, but I've been eyeing one. But if a deep socket works (re: prev. post), I'll certainly try that as well.

Thanks for the replies guys.


what are you guys smoking,

How'd you know?

[1991PDX535i]

Just bought my 1991 535i/m and had it scheduled for an evaluation at Pacific Motorsports. We figured I could do the 02 before the diagnostic. Took me all day with the special tool and a river of WD40. Finally had to give up very frustrated. Cost me the $95 shop fee and it apparently took the tech all of that hour.
Bottom line: OBC MPG was lying. Got 23 MPG over 2100 miles PDX to Las Vegas and back. OBC claims 11.3 MPG.

[762Armo]

hmmm. Took less than a minute on my M20 to replace... Now I'm wondering where and what the M50 O2 sensor looks like.....

[jint45]

More like what are YOU smoking?:confused
Try it on a '95 525 and then report back.
Not all E34s have the same engine/exhaust set up.

I have changed a bucket of those O2's on 525's, 525 exhaust configuration is actually the easiest to work on when it comes to the O2.

[upallnight]

I wouldn't. That suckers usually in there and grabbing two sides usually isn't enough. If all else fails, cut the wires off and use a real socket.

Why do people buy ta special tool to remove the 02 sensor when they are going to replace the 02 sensor? Like AHenry014 stated just cut the damn wire and use a regular socket. You can use an open end wrench to put the New sensor back on.

[bubba966]

Got that set from HF and still wasnt ablel to replace it; much too tight up in there. I had no choice but to drop the exhaust which would have saved me time if I just started there. Its amazing how you guys can do it without dropping the exhaust, but i needed to with my wagon. Whatever, its done now.

Exactly what I did on a 525iT. Tried the PB soak & O2 socket and couldn't get it. Was still a bitch with the exhaust off and out from under the car. :mad

At least the M60B40 sensor is easier to get to, I don't expect to have to drop the exhaust on that one. Just :( that there's two of them...