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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 07-04-2012, 03:48 PM   #1
Registered User
Join Date: Mar 2004
Location: Atlanta
Posts: 181
My Ride: 2009 328 wagon
catalytic converter/exhaust manifold replacement DIY

It's been a couple days since I finished replacing my catalytic converters, and now I have a little energy built up to write up the DIY ;-)

I'd say this is a 7 on a 1-10 scale of difficulty. Nothing crazy, just lots of pieces! Most importantly, I advise any long-term BMW owner to purchase an engine-support for maintenance on their car. I bought mine from Harbor Freight for $80 and used it to change out motor mounts a few months ago. It comes in handy for changing cats as well as oil pan gaskets... something everyone with a car over 100k miles will soon have to do.
FYI, my 2000 323it has 240k miles on it. The cats went out around 235k. I changed O2 sensors around 120k and then again at 230k when I got O2 sensor codes. As soon as I swapped them this time, the Catalytic converter inneficiency code poped up... oh oh!!

* Parts: I purchased Pace Setter cats on eBay for $300 each. Turns out I accidentally ordered the wrong front cat/manifold. The manifold for 2001-2005 325 does NOT fit the 98-2000 328/323 front manifold. Pictures show why. I couldn't find the correct Pace Setter front, so bought unknown brand front manifold from BavAuto for $360. Also buy 16 new exhaust manifold nuts and a handful of studs, as well as new gaskets for the engine-to-manifold as well as manifold-to-exhaust pipes. Nuts and gaskets MUCH cheaper online. Dealer is outrageous.
* Tools: As mentioned, the engine support/brace is worth its weight in gold. Also, a 1/4" socket wrench, a 11/2" extension, and 11mm deep well socket will get most of the manifold nuts off. A 11mm racheting box end wrench really saved the day for a couple nuts on the rear manifold. Various other 13mm & 16mm sockets are used for the rest.
I'm skipping the basic steps that other DIYs cover.

* Step 1- Remove the plastic engine cover (to access O2 plugs), and cabin filter housing like we've done a million times before. Remove the Secondary air pump/smog pump as well as the valve on the engine block and associated hoses. This only takes a couple minutes w/ a 10mm socket and really opens up access to the top of the manifolds. NOTE: remove the air pump mounting bracket as well (3 10mm nuts). I kept hitting my knuckles on the bracket and realized how easy it was to get out of the way.

*Step 2- Jack the car up. Remove the frame cross-brace w/ the 4 16mm bolts for access to the bottom of the manifold. Use the engine support/brace and just jack the engine up engouh to take the weight of the motor mounts (1/4").
Remove the driver's side motor mount.

pic1- engine support, pic2- air pump mount, pic3- pump mount removed, pic4- wrong front manifold, pic5- correct manifold
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Last edited by beberle; 07-05-2012 at 07:23 AM.
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