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      12-10-2011, 12:01 PM   #1
MFGJR
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Drives: 2007 Z4 M Coupe
Join Date: Sep 2008
Location: Richmond, VA

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Blacked Out Mufflers & Remove/Powder Coat Exhaust Tips DIY

While I was dealing with the aftermath of the Attack of the Teutonic Mice (http://www.zpost.com/forums/showthre...ighlight=mouse), I figured it was a good time to paint the mufflers—which we all know are kinda distracting hanging there under the rear bumper like a big pair of stainless steel cajones. And, I’ve been wanting to powder coat the exhaust tips black, to go along with the rest of the blacked-out trim and badges on the car. None of this is rocket science, but I came across a couple things that might be helpful to someone wanting to do the same.

Regarding removing the mufflers and, quite importantly, adjusting them when reinstalled, consult this great DIY by crfine88—thanks to him for the excellent info: http://www.zpost.com/forums/showthre...ust+diy+stands

Once the mufflers are off, you need to drill out the three rivets holding each tip onto the muffler. Note that one of these rivets is on the top of the tip, and so you have to either drop the muffler or remove the bumper to get at it. Dropping the muffler is probably the easier of the two. A few months ago, I asked my body shop guy to drill out the rivets and pull the tips off while he had the bumper off. He reported that they drilled out the rivets on one of the tips, but were unable to get the tip off, even with a slide hammer. They assumed that they were pressed on tightly, and/or had corroded inside, and weren’t going to come off. So, they gave up. I’m more persistent, however, and easily found the problem: They only drilled out the head of the rivet, but left the shaft inside and this had the tip locked on. To get the tips off, first squirt a little PB Blaster or the like in between the tips and the muffler outlets a day or two before. Then drill out the head of the rivet, and using a punch to tap the rivet out (I actually used a nail set).

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You should see a clean hole, consistent in diameter, through both the tip and the outer layer of the muffler outlet. Note that the muffler outlet has two layers, and the hole is only in the outer one—so, you can’t see all the way through to the interior of the pipe. You should be able to insert a punch at least a quarter inch into the hole—if it barely goes in, some of the rivet’s still there.

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Once you’re sure the rivets are completely gone, you may be able to twist and pull the tip off. If not, use a blunt chisel and hammer to GENTLY tap the rear edge of the tip to dislodge it. Take your time, and move around to different points on the tip.

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The tips are two layers, and the muffler outlet has two layers, and they interlock when installed. You can see the construction in this pic:

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Next clean the mufflers thoroughly with a scrub brush and 3M pads and a degreaser like Simple Green, so that you get good paint adherence and finish. You may need to use a solvent if you have tar on them, and possibly do some light sanding. A ladder makes for a convenient way to hang the muffler for painting—use some sturdy wire as those OE mufflers aren’t light.

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I painted the mufflers with hi-temp, semi-gloss spray paint intended for barbecue grills. Follow good, basic spray painting technique—don’t start/stop the spray on the part, and apply several light coats, with 5-10 minutes in between, rather than a heavy coat that will run or orange peel.

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I cleaned up my tips with solvent and a 3M Pad, and took them to the local powder coater. You’ll want the shop doing the coating to mask the interior of the tips, where they mate with the muffler, as you don’t want excess material in there that will make getting the tips back on the muffler difficult. And, talk with the shop about where/how they will attach the ground wire to the tips. They evidently attached (soldered, by the looks of it) the wire to mine at the exit end of the tips, and each has a tiny flaw in the coating where it was grounded. While I admire their diligence in getting a good ground, necessary for good, even powder adherence and finish, it seems like they could have attached it on the interior of tip to avoid the flaw. It wasn’t bad enough to warrant having them re-done, though someone more anal might think differently.

To reinstall the tips, clean the muffler outlet with some sandpaper, line the holes up and tap the tip on with a rubber mallet. Install new rivets—which theoretically should be stainless steel. I couldn’t find stainless, and so used aluminum. There will probably be some resultant corrosion at some point, but I’ll just keep an eye on it. Note that I already had the mufflers back on the car at this point, and so only installed the two rivets on the bottom of each tip. They’re on tight and don’t rattle, so I’m just leaving the third, top rivet out for now. Adjust the mufflers and/or bumper as necessary using crfine88’s instructions.

Here are the results:

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And, now everything matches, even the dog!

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