Exhaust manifold question

[Jimbo65]

Hello all, my question is: Would an exhaust manifold/ catyletic convertor from a 2.5 work on a 3.0 (Z4) ?
Specifically, I am refering to the CYL 1-3 manifold.
I know the ports on the head are the same, and they are both M54. I realize they do have different part numbers (by 1 last digit), and the gents at the BMW dealership could not answer the question. I have a 2003 Z4 with the 3.0i and am getting the P0240 code with the bank 1 below threshhold. I am currently running fuel system cleaner through according to instructions, but am preparing for the worst. I have located a good bank 1 exhaust from a 2.5, but am hesitant to buy without knowing for sure on the interchangeability.
I found this at a price MUCH cheaper than the $861.00 cost of the new replacement from BMW.
Some history of the engine: I have had to replace the head on my engine due to a crack @ CYL 3 port, and never had the P0240 code even prior to getting the bad head diagnosed and replaced...it just gave a misfire on cyl 3.
The engine has just over 100,00 miles on it and sure runs good after the hefty repair. Now I am faced with this new issue with the emissions.

Any insights would be greatly appreciated!


Cheers-


James

[Lord Vader]

The M54 block is the same, even if 2.5 or 3.0L. The exhaust maniold should mount up the same and be identical. Their should not be a difference as long as the mounting points are the same to the block, and to the Cats.

[Jimbo65]

Thanks for the Reply Lord Vader, I looked at the image for both parts on the BMW site.
Either they use the same illustration for both parts, OR they really are interchangeable.
Do you have any insites of cleaning the cats? I have heard of a "citric acid bath" where you use a diluted mixture and let the manifold/ cat soak for 6-8 hours. I am really looking for a least expensive way around the new-manifold/ cat. from the dealership.
Thanks again for your time!

Cheers-


James

[Lord Vader]

Honestly i have never heard of someone "cleaning the cats". I usually hear of people replacing them when they became clogged. Thats what i did for my mother-in-law's car.

The cats are pretty expenisve, but its because they contain Platinum and other precious metals. With platinum being worth more then gold, ounce for ounce, im not suprised.

[Jimbo65]

I located a unit off of a 2.5...did some reading, and am going to try the 8-hr. soak in 50/50 citric acid and water. Will post results when it is completed.

[Jimbo65]

Here is an update.
I used fuel treatment kit by CRC called "CRC Industries Guaranteed To Pass® - Emissions Test Formula".
It was used it according to directions, and I went in and erased my P0240 code.
Three days passed before the code reappeared; verified by the SES light on the dash.
My code reader came back on with a red light and the dreded P0240.
Anticipating this situation, I ordered another Bank 1 manifold assy. (at a great price) .
Knowing there was some time before the new manifold arrived, I decided to try one last product.
The product is made by Prestolite Performance and called "Cataclean" fuel and exhaust system cleaner.
Once again, I used the product according to directions while erasing the existing code in the process. Today was day 3 with no SES light, but figured it was just around the corner. I was going in for the emission test today, and figured I would plug in my code reader before I left the house just to see if I might have a yellow or red light.
IT WAS GREEN ! NO CODES TO REPORT!
I was floored...was it a combination of both treatments? was it just the Cataclean?
Just do not know for sure, but I do know this...I passed emissions with Flying Colors.
Well, now I have a fresh manifold to put away when it arrives....you know, it does not bother me one bit. I am not sure if my situation was an exception, but I strongly recommend these chemicals to anyone faced with the cost of a new manifold and the dreaded P0240. Two tanks of premium fuel and about $40.00 in treatments saved a lot of headache.

Cheers! James