E36 Exhaust Replacement and M3 Exhaust Upgrade

Note: This repair applies to all E36 BMW models with six cylinder engines, including all 325i, 325is, 325ic, 328i, 328is, 328ic, 323i, 323is, 323ic, and M3 models. Four cylinder engine E36 models may have slightly different exhaust routing, clamps, gaskets, and hangers. Be sure to consult the Bentley service manual if you have unanswered questions after reading this. After nearly 190,000 miles of service, the OEM factory exhaust on my 1995 BMW 325is was looking and sounding pretty sorry. The muffler's internal baffles had broken down and the result was a very raspy, wheezy, loud, and harsh tone. The muffler and twin tailpipes were beginning to exhibit signs of rot as well. I found a local E36 M3 owner who'd upgraded to a Supersprint exhaust shortly after buying his car and therefore had the stock M3 exhaust system lying around in his garage. I got it for only $25, a steal when you consider that the local BMW dealership gets over $1000 dollars, and used E36 M3 exhausts typically sell for between $75 - $200 plus shipping on the internet. The first step was to pick up the new exhaust collar gaskets, plus 4 new nuts and Bbolts, at the dealership. This came to about $40. In hindsight, I should also have order muffler hanger brackets as well, but we will get to that. Back home, I waited til a saturday morning to begin the project. I used the factory BMW jack to raise the car via the sideskirt slot, and supported the vehicle with jackstands. I sprayed PB Blaster penetrating oil on the exhaust bolts and rear muffler hangers, and let it sit for some time before breaking out a steel-bristle brush to scrub away corrosion and grime from the nuts and bolts before attempting to loosen them. Had my BMW not spent the past 12 years in the northeast as a daily driver, the nuts and bolts of the exhaust system would have likely been in better shape. I ended up using a small hacksaw (the kind the blade slides into the handle of) and Stanley 'contractor grade' 18t and 32t hacksaw blades to cut all four bolts where the catalytic converter meets the cat back exhaust. A dremel or similar rotary tool with appropriate cutting wheel would probably also work well. I used vice grips to pull the ends of the bolts out afterwards. Turning my attention to the rear muffler hangars, I managed to break off both nuts/studs on the clamps that grip the muffler in place. Six cylinder engine E36 BMWs have a (overly) well engineered rear hanger setup that consists of two rubber hangers with two piece metal brackets/clamps that grip the muffler by the protruding pinched seams and hold it in place. After breaking both nuts off, the lower plates fell off, and the exhaust was shaken loose and fell to the ground. Now we had a problem. It was 2 days before Christmas, a Saturday afternoon, and the parts depts would not re-open again for 3 days. I got under the car, and used a 13mm socket (same size as the exhaust bolts), 13mm box/open end wrench, and a trusty pair of 10" Vise-Grips to remove the 4 semi-frozen and loctite-d on nuts holding the rubber hangers to the underside of the car. Once I had the 2 entire assemblies off, I took them to my workbench. Using a 13mm socket and 13mm wrench, I removed the metal bracket (with the brazed/welded bolt for the lower clamp and broken-off end) from the rubber hanger assembly. I used a grinding disc or two and my Dremel tool to grind off the head of the welded nut, then fipped the brackets over and pounded on the stud with a hammer, breaking it free. I replaced it on each side with M8x40 metric bolts, washer, lock washer, and nut for a solid and strong throughbolting setup. Thus eliminating the need to order anything from the BMW dealership. Both rubber hangers looked okay, but we shall see how they cope with the heavier M3 exhaust. To reassemble, I first put the muffler hanger assemblies back together and reintalled them onto the underside of the car next to the gas tank. To get the exhaust in, you really need a second person to help you. Have your helper guide the twin pipes and collars into position, installing the copper gaskets in the correct locations (the thicker one goes on the pipe with the recessed collar), and just pushing the bolts through for now. Then, make sure the hanger is gripping the muffler seams, and tighten it as much as you can with a socket and ratchet. When tightening the exhaust bolts, tighten all four evenly so the collars tighen evenly. Use a torque wrench for the final snugging-down. Double check your work and start the car to make sure there are no leaks. I found that installing the E36 M3 exhaust on my 325 eliminated the rattling, buzzing, harsh, and loud drone, and resplaced it with a mellow burble of an exhaust note. Quiet, but sounds authoritive and powerful when you rev it up. A nice upgrade! Total costs? $25 for the exhaust and $40 for the bolts, gaskets, nuts, and washers.