Top or bottom, which is it for o2 sensors during downpipe install

medphysdave · 05-14-2023, 10:35 PM

I've searched the forum, watched YouTube videos and it seems like a split verdict on the thought that the top method seems pretty easy, but concern about rerunning the O2 cables into the clips is a concern. Some seem to go from below and say it's easy. Just be careful to not twist the wires.

My interpretation is that through the top might seem like a longer process, it is pretty quick to get to the O2 plugs. The bottom can be faster if you get lucky and can manage to disconnect and reconnect the plugs easily as the DPs are being installed.

I'd have a quickjack setup for this. Lowering the exhaust is straight forward. Can't seem to determine which pathway is best.

tailhappy · 06-02-2023, 10:52 AM

After doing this myself, two time now. It is easier to remove the engine covers to access the 02 sensor plugs at the rear of the engine. Unplug them. Raise the vehicle. Unbolt the cats from the midpipe. Then loosen the v-bands to the turbos. Remove the smaller cat first. The longest one lastly. The 02 plugs will only fit the one its mated too. So mark one as to not mix it up.
Took me about seven hours all total to change them out. Working from the floor in my garage didn't speed up the process. Not being able to code out the readiness of the system, making this questionable.

medphysdave · 06-02-2023, 12:10 PM

I did everything from the bottom and would not recommend it. If I find myself doing it again I'll go in from the top. Even if it takes me just as long I find much more pleasant working in the engine bay from above.

05-14-2023, 10:35 PM	#1
medphysdave Brigadier General 4560 Rep 4,672 Posts Drives: M2 CS \| 85 of 592 Join Date: Apr 2015 Location: Charlotte, NC iTrader: (3)	Top or bottom, which is it for o2 sensors during downpipe install I've searched the forum, watched YouTube videos and it seems like a split verdict on the thought that the top method seems pretty easy, but concern about rerunning the O2 cables into the clips is a concern. Some seem to go from below and say it's easy. Just be careful to not twist the wires. My interpretation is that through the top might seem like a longer process, it is pretty quick to get to the O2 plugs. The bottom can be faster if you get lucky and can manage to disconnect and reconnect the plugs easily as the DPs are being installed. I'd have a quickjack setup for this. Lowering the exhaust is straight forward. Can't seem to determine which pathway is best. __________________
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06-02-2023, 10:52 AM	#2
tailhappy New Member 0 Rep 11 Posts Drives: BMW M2 Join Date: Feb 2023 Location: NC iTrader: (0)	After doing this myself, two time now. It is easier to remove the engine covers to access the 02 sensor plugs at the rear of the engine. Unplug them. Raise the vehicle. Unbolt the cats from the midpipe. Then loosen the v-bands to the turbos. Remove the smaller cat first. The longest one lastly. The 02 plugs will only fit the one its mated too. So mark one as to not mix it up. Took me about seven hours all total to change them out. Working from the floor in my garage didn't speed up the process. Not being able to code out the readiness of the system, making this questionable. Attached Images
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06-02-2023, 12:10 PM	#3
medphysdave Brigadier General 4560 Rep 4,672 Posts Drives: M2 CS \| 85 of 592 Join Date: Apr 2015 Location: Charlotte, NC iTrader: (3)	I did everything from the bottom and would not recommend it. If I find myself doing it again I'll go in from the top. Even if it takes me just as long I find much more pleasant working in the engine bay from above.
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