Yesterday, I installed a replacement muffler on my beloved 1987 BMW 325. As I recall the work is slightly different on earlier models, and on the 325i models too.
The replacement muffler I was installing was not new, but it was an original BMW part as implied by the BMW stamp on the main muffler box. It seemed to be in good condition (and subsequently proved to be).
I did this work alone, and without the car jacked or hoisted up in the air.
The first step was to get the muffler raised up. Doing so on either end would be problematic, so I attached the center hanger first. A 13 mm bolt goes into the body to keep it in position.
With the muffler basically hanging at the approximately right height, I tried getting the front part connected and that didn’t work for me. I realized this would be easier to do once the rear clamps are on, so that’s what I focused on next.
The clamps consist of two sets, one more forward and one more rearward. Side to side, they are approximately mirror images. The donut-shaped hanger will eventually have the little thicker section separating the top and bottom, but to get it on, I had to rotate it. It was difficult for me to get the hanger onto the car and then onto the clamp too, but with lots of patience I managed. I did some prying with a screwdriver or two but in the end, what made it work best was to have the hanger rotated just barely enough to get in. In retrospect I should have done this without the muffler already in position.
The nuts for the bracket are special 13 mm nuts, three of which are accessible via a normal 1/2″ socket and one of which required the smaller 1/4″ socket to get in there. Had I removed the tire, the space constraint would have not existed.
With the clamps tightened fairly well, but not all the way, the muffler was in position well enough to approach the front of the connection. The relevant nuts and bolts age well by general standards but still, 25 years is a long time so I replaced the nuts, bolts and gasket with new ones.
The nuts are at the forward end of the bolt-and-nut combination, and they’re 12 mm whereas the bolt heads are 13 mm. I had some issues getting the gasket in position so it might need to be positioned just so before being put into its final location. From then on, tightening the three bolts and nuts was easy.
With the knowledge that the muffler was now in the right position, I went back to the rear of the car and finished tightening the clamps.
I started the car and it sounded nice, and ran, very nicely.