E46Fanatics - View Single Post - catalytic converter/exhaust manifold replacement DIY
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Old 07-04-2012, 04:33 PM   #3
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Join Date: Mar 2004
Location: Atlanta
Posts: 181
My Ride: 2009 328 wagon
*Step 7- install rear manifold/cat and then front manifold. The new manifolds do not come w/ pressed studs like the factory cats. It's easier to install this way. I could get a torque wrench on most of the nuts. The ones I couldn't, I attempted to hand-tighten to match the others. Another benefit of using a 1/4" drive is that it takes a good bit of force to get 15ft/lbs and not break a mounting stud! - Note: it's easier to install the rear o2 sensors on the manifolds BEFORE mounting the manifolds to the block. No clearance problems. the front o2 is easily installed from top.

*Step 8- I found almost no play w/ the manifolds sitting on the mounting studs. Luckily, these aftermarkets pieces fit pretty well! However, there was a 1/4" difference in manfold lenghts between the two. Luckily I was able to put a couple washers under the little manifold cross-brace to level them out. Tightening the nuts pulled the rear pipe into position.
-The rear manifold required 3/8x11/2" and 3/8"x2" bolts with associated nuts and lock washers. Don't use stainless steel, it supposedly stretches when hot. I used grade-5 hardware. The rear Pace Setter was threaded for a 3/8" Standard thread in the flange, so no nuts required, but I used a lock washer under the bolt head. Two 3/8x11/2" bolts.

Step 9- put everything back together. Engine mount. frame brace. secondary air pump. That's it! I had disconnected the battery prior to work, so I cleared the codes and the car was ready to re-map to the new cats when I was done.

No more check engine lights! These cheaper after-market cats have a 2-year warranty; I hope they go for at least 4! It took me about 7 hours over the weekend. I hope this DIY saves you some time. Now, Here's hoping I can make it to 300k

pic 1- gap between two manifolds pic2- gap solved w/ washers pic3- new studs replacing ones that came out pic4- pretty new manifolds/cats installed!!
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Last edited by beberle; 07-04-2012 at 04:40 PM.
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