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Discussion Starter · #1 ·
Hi Guys and Bluebee,
I eventually fitted The Precat Oxygen Sensors that was wrongly ordered durin December 2010, but now I have a small problem.

When I unplugged the Sensor Wires from the top of the Engine and removed the removed the old Sensors (First time after 208000km), he two little steel clips that hold the wires in place so as not to touch the exhaust pipes, just fell off.

After fitting the new sensors, I can not, for the love of me, find the place or hole or plate where they are supposed to by mounted. In the mean time I secured the wires by tying them to the bulkhead with an electrical plastic strap.

I know there will not be any photos on this and the sketches that I googled, shows no such securing places. Can you Please Help.

Pensioner
 

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Older than old school
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Hi Guys and Bluebee,
I eventually fitted The Precat Oxygen Sensors that was wrongly ordered durin December 2010, but now I have a small problem.

When I unplugged the Sensor Wires from the top of the Engine and removed the removed the old Sensors (First time after 208000km), he two little steel clips that hold the wires in place so as not to touch the exhaust pipes, just fell off.

After fitting the new sensors, I can not, for the love of me, find the place or hole or plate where they are supposed to by mounted. In the mean time I secured the wires by tying them to the bulkhead with an electrical plastic strap.

I know there will not be any photos on this and the sketches that I googled, shows no such securing places. Can you Please Help.

Pensioner
Does this help?

 

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Discussion Starter · #3 ·
Hi Bobdmac,
Thanks for your reply, but NO. The engine in the photo appears different. Maybe a V8? I have a straight six (M52TU)and my oxygen sensors can only be removed from the bottom of the engine (my opinion). I have hands that are bigger than the space between the Fire Wall and the Rear of the engine. I can bearly get my hands in, and allthough I can feel some projecting steel plates, I can not find the place where these brackets (clips) can go. I have more blood on my hands than in my body from all the small cuts I obtained and one can't see either.

I will take a drive to BMW today. Maybe they will be kind to tell me!! Will let you know though.
 

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Older than old school
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Weird. The caption says it's for the m54TU and M54 engines. Oh, well. Chalk it up to another Bentley's error, I guess.
 

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Discussion Starter · #5 ·
Hi Bobdmac,
I have solved the problem. One should look carefully. I found two plastic lugs at the rear of the cylinder head, just underneath the spark plug cover end. Those were the only two places where these wires can go (unless I am mistaken). But it looks right. The clips must have opened during the years of vibration and had fallen off and that may be the reason why I thought that they were to be secured way down. Any way it is done and thank you again.

The M54 and M52TU can not be the same engine. But I am happy.:thumbup:
 

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Freude am Fahren
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Precats cannot be changed from underneath the car; post cats maybe. I haven't looked for them yet. I assume you meant post cat sensor?

Bentley image is correct for precats on m52,m54 engines (which share heads so the exhaust manifold is largely unchanged.
 

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Discussion Starter · #8 ·
My car has a M52TU six cylinder engine and there is no way that Pre-cat sensors can be removed from the top and that is only my opinion. I had to remove the Oil Pan Protection Plate to get sufficient clearance to remove and replace the Oxygen Sensors. One can barely see the sensors from the top where they fit into the Exhaust Manifolds (Cyl. 1-3; Cyl. 4-6). And if I am correct we drive the same car (mine is a Right Hand Drive). 1999 528i Steptronic. Built 6/99 209000km's. I only hope that it will now be less thirsty!!! But thanks for the input.
 

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Maybe non-US cars are different from US cars.
 

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I just replaced the precat O2 sensors on my M52. The front one you can see from above. I was able to get it loose with an open end wrench from above, but there was no way I could get it out any other way than from below. I put the new one in from below and put the final tightening on it from above. For the rear sensor, you can't even see it from above. That was done entirely from below.
 

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Freude am Fahren
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Odd. I can see absolutely no way for me to access my cats from below. They're RIGHT THERE when you pop the hood; you'd have to reach past the entire block to get to them from below, and then you'd be working entirely blind. :dunno:
 

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Discussion Starter · #12 ·
Hi Guys,
I have no idea how to place a photo on this forum to show any particular item, but I will try today. First things first. I will take a snapshot of the engine from the top and the place where I secured the wires. It could be good for a laugh or two!!:D Watch this space!!
 

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Discussion Starter · #13 ·
Hi daw,
Where are the Sensor wires secured on your engine to ensure that they will never touch the exhaust pipes? I had a hard time to figure that out and although it is done, I am still not sure. I don't want them to dislodge and touch the hot pipes on open roads.
 

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Discussion Starter · #15 ·
Thank you, daw, I will look again tomorrow in the sun light. I really could not see it. Lucky me, I had a few Electric Cable Ties. Did it around the Air Con tubes also. I'm a Klutz for not seeing it the first time. Thought I found the correct place on the cylinder head! I took some pictures, but I tried to post them on the Reply Thread, but it did not work. Maybe I have the incorrect Software!!
 

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I just removed mine, it is done from below. Easy to get to, took less than 3 minutes. I don't see it being easier from above. Of course I dropped a 6inch extension yesterday near the exhaust manifold and it disappeared. I looked for it for 20 mins and gave up. Maybe I will see it soon.
 

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I can confirm that on 1997 (made in April) 528i there's no way you can change them from under the hood unless you have flexible hands :) Only one possible way is underneath the car. I did mine just a week ago with help of special flexible O2 wrench (long handle, flexible head).
 
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