2008 E92 328xi Pre-LCI Exhaust Manifold Replacement (Bank 2) Explained P0430

[jumpmanonlyE92]

This forum is to explain a little more in depth what the process is like replacing the catalytic converters (exhaust manifolds) Bank 2 specifically in my case. The car I will be talking about is a 2008 E92 328xi coupe N52 pre-LCI. This information can help you replace which ever cat you need to switch. Before saying anything further, I must outline that in order to change bank 2, you must drop the entire exhaust and remove Bank 1 to be able to get rid out of Bank 2.

To begin, the first issue you must tackle is, do you have what it takes to remove the exhaust bolts on the exhaust flange connections? This is probably the most nerve racking task to accomplish because its different for everyone. My bolts and entire flange happened to have seized up all together. Applying pb blaster and letting it sit overnight is always a good first step. The studs that hold the cat to the exhaust are most likely heat pressed/welded onto the cat. The nut is really what keeps everything together. No washer, just the gasket in the middle inside of the junction.

To remove/separate the flanges and bolts I did the following:

1. Find my long sockets that will fit the nuts respectively. (They may not all be a 13mm)
2. Have a premium blue flame torch, heat gun, and wire brush as my main tools
3. Have a construction switch blade, pb blaster, freeze off spray, and a flat screwdriver for my back up tools
4. Have a breaker bar, impact gun, and/or an air impact gun.

When looking at the exhaust flanges, you will notice a hardened coating. Compare the luster of the exhaust down pipe vs the flanges themselves. This is the problem nobody talks about. There is build up all around these things whether you see it or not. The goal is to free all of the exhaust from its build up until you can take the nuts off and get in between the flanges carefully to prevent from bending the flanges and separating them from the exhaust manifolds. This is a game of patience.

My protocol was as follows and although it was tedious, I am satisfied with the results:

1. Heat the nut and thread end bolt to anything past 950 degrees Fahrenheit. Once temperature has reached this threshold, continue holding heat for a minute to two minutes to really tackle on the build up to start loosening that up.
2. Take a wire brush and clean the nut and bolt threads and where to the brush allows quickly. You will notice less and less dust coming off the hardware. This is your sign to move to step 3.
3. Get pb blaster and coat into the threads, inside the nut, and around the flange seal. It should burn off as you apply it but this makes the pb blaster work in some critical areas.
4. Spray freeze spray all over the heated areas for 20-30 seconds and watch it penetrate the build up along with the applied pb blaster.
5. While still hot, clean again with a wire brush all around hard ware and repeat steps (1-5) again about 3 good times to assure you have the chance to remove the bolts.
6. After repeating the cleaning sequence, repeat step (1) once more and try to remove the nut you’re working on with its long socket with your choice of impact. The hammer of the impact should be enough for the nut to break through the buildup pulled in reverse.
7. Repeat for all nuts.

Again, the stud bolts won’t be coming out. Your cats are dead and you don’t need to worry about it. If you are replacing only one exhaust manifold and reusing the other, take it to a muffler shop to have them out. This is the only part of the process not worth the time and stress. Add new hardware after when reinstalling.
Once you have the bolts out, it’s time to separate the flanges apart. To do this, it may help removing the first exhaust pipe support to get some leverage but isn’t necessary.

My process was similar to the removal of the bolts:

1. Heat one side of the flange at a time up over 950 degrees Fahrenheit with a torch. Once temperature has reached this threshold, continue holding heat for a minute to two minutes to be able to clean the junctions.
2. After heating, give a pass with a wire brush into the flange junction and apply pb blaster to let it work off the grime when you come to use the construction switch blade.
3. Apply freeze spray immediately after applying pb blaster and hold for 20-30 seconds on the flange.
4. Use a wire brush to flake the newly freed up build up and start scraping at the junction on both sides of the gasket all-round until you clear out enough build up to get a flat screwdriver in there.
5. Hit the flat with a 4lbs metal mallet until you get a break in the seal all around
6. Pry/separate exhaust from exhaust manifold.

You did it! You did the hardest part to guess at. The next step is to remove all o2 sensors and the 8 11mm nuts each manifold has from the headers. Once you get those out you have to drop the exhaust which I won’t cover because there is plenty of information on here, YouTube, and elsewhere. Also on header hardware locations and replacement.

You have to drop the cats from the bottom unless you can manage to lift Bank 1 from the top, and then perhaps Bank 2 from the top as well. You have to drop the exhaust to be able to remove bank 2 from the bottom if you can’t get it out from the top.

Once everything is out, go back down the steps in reverse order to put the hardware back in. Always put in Bank 2 first.

Happy wrenching!

-Jumpmanonlye92