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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Tue, Mar-18-2014, 06:03:03 PM   #11
cozmo kraemer
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Default Re: Pre-Cat O2 sensor DIY?

I did mine with a 7/8" wrench I cut in half. Works great. I have had my headers out of the car...more times than I care to count...and I antiseize the o2s every time i put them back in, so it isn't tough. Break them free with the wrench and then unscrew them. I can do them from the top in about 10 minutes.
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Old Tue, Mar-18-2014, 09:33:01 PM   #12
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Default Re: Pre-Cat O2 sensor DIY?

Quote:
Originally Posted by cozmo kraemer View Post
I did mine with a 7/8" wrench I cut in half. Works great. I have had my headers out of the car...more times than I care to count...and I antiseize the o2s every time i put them back in, so it isn't tough. Break them free with the wrench and then unscrew them. I can do them from the top in about 10 minutes.
how do you get any leverage to loosen them?
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Old Tue, Mar-18-2014, 10:15:30 PM   #13
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Default Re: Pre-Cat O2 sensor DIY?

They aren't heroically tight. Doesnt take a ton. Like I said, they have been out of the headers a bunch of times. If you were taking them out for the first time, it might be much tougher, or not possible with my method.
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Old Tue, Mar-18-2014, 10:21:34 PM   #14
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Default Re: Pre-Cat O2 sensor DIY?

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Originally Posted by cozmo kraemer View Post
They aren't heroically tight. Doesnt take a ton. Like I said, they have been out of the headers a bunch of times. If you were taking them out for the first time, it might be much tougher, or not possible with my method.
I'll keep that in mind.

So you can get to both of them from the top with the wrench?
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Old Wed, Mar-19-2014, 12:39:42 AM   #15
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Default Re: Pre-Cat O2 sensor DIY?

they were on tight when I did mine. With my breaker bar, it was still tough. Something snapped, and I was afraid something broke, but it was just the sensor coming loose.
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Old Fri, Mar-21-2014, 10:42:09 PM   #16
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Default Re: Pre-Cat O2 sensor DIY?

http://www.billswebspace.com/BMWZ4MS...stallation.htm
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Old Fri, Jan-02-2015, 04:38:31 AM   #17
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Default Re: Pre-Cat O2 sensor DIY?

All the advice here is very helpful for those with an M3. One change I made from Waldron80's illustrations regarding access to bank 2: rather than suffering with the very limited space as he photographed, go to the left side of the exhaust where there is much more room. I used the series of extensions and O2 sensor removal tool for removal (PITA) but, when installing the new one, realized the driver's side, from under the car, was much more user friendly.

Removal, excluding the overnight wait while WD40 did its job, took a couple of hours; install from the bottom, left side, was 5 minutes.
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Old Fri, Jun-05-2015, 05:46:33 AM   #18
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Default Re: Pre-Cat O2 sensor DIY?

Thanks for sharing great info. I'm going to do this pretty soon. Does anyone have part number for Pre Cat bank2 O2 sensor?
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Old Mon, Jun-08-2015, 10:53:28 PM   #19
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Default Re: Pre-Cat O2 sensor DIY?

I found some info from this thread, http://www.m3forum.net/m3forum/showt...ghlight=sensor.

Pre cat bank 2 oxygen sensor
Part#: 11781405324
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Old Tue, Jun-09-2015, 01:09:37 AM   #20
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Default Re: Pre-Cat O2 sensor DIY?

yea it takes some time to figure out. i just replaced both my pre-02 sensors a few months back. takes about 15mins to figure out how to tackle the job with various extensions, adjustable ratchets, swivel joints, and the 02 crowfoot socket. i definitely wanted to avoid removing headers. lol that would have been a PITA.
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Discussing Pre-Cat O2 sensor DIY? in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)