As cars get more modernized to pass national and state emissions standards, the exhaust systems are becoming more complicated. Replacing mufflers was never easy for a backyard mechanic, and nowadays it does not come highly recommended. However, if you have an old car and there’s clearance underneath, you might be able to do this job in your driveway or backyard.
1. Lift the vehicle safely and securely on the car lift. If it’s a drive-on lift, even better. Put on safety glasses.
2. Size up the job. Locate the muffler. If it’s original equipment, chances are you’re going to need more than a muffler in the aftermarket world. Inlet pipes and tailpipes do not always come with aftermarket mufflers. If you do not see a clamp or flange near the inlet of the muffler, you need to replace the exhaust pipe as far as it goes to the next connection, unless the inlet pipe happens to be going straight into that muffler for at least 5 inches. If that were the case, you could cut the pipe and install the muffler and clamp it. If there is any curve on the inlet pipe before it directly goes into the muffler, you’re going to have to replace more than the muffler. The problem is the inlet of the aftermarket muffler is straight and if you try to cut the pipe on a curve, it’s going to compromise how the muffler fits onto it. If there is a clamp on the inlet pipe and muffler connection, try to determine the condition of the pipe at that connection. You have to be able to heat up that junction between the muffler and the inlet pipe and then be able to separate the muffler from the inlet pipe without incurring damage to the inlet pipe. Two types of inlet pipes are a hop-over or hop-under pipe (meaning hopping over or under the rear axle) or an intermediate pipe that may go all the way to the catalytic converter junction. The type of application will dictate how much you have to replace. In flange connection applications carefully inspect the flanges on both sides because you’re going to have to cut the bolts out with the torch and not compromise the other connecting flange. Ideally, this is something you’ve either looked at already or had an idea of what you were going to need, so the replacement parts should be already at hand.
3. Put on the safety gloves and swap the safety glasses for cutting glasses. Clamp the connection; Light the torch and cut the clamp halfway down on both sides and tap it off with a hammer. Then heat the connection of the muffler inlet and pipe until it is glowing red. Turn off the torch and try twisting the muffler back and forth (be careful because the torch will make the surface of the muffler and pipes very hot, so do not attempt to do this without safety or cutting gloves). Keep twisting the muffler one way and the next as far as it will let you and when you get enough movement from the muffler pull or push it off the pipe to free it. You may have to relight the torch and heat up the inlet connection repeatedly until you’re successful.
Light the torch and cut the flange bolts out from the muffler side and then tap on the pipe (on the side you’re replacing) with the hammer until it separates. If there are still pieces of bolts in the inside flange, heat up the ears with the torch and when it’s glowing red, give the bolt(s) a quick tap with the hammer, but not enough to bend the flange. For the cutting pipe connection, if you happen to have one of those very rare type cars that allows you to just replace a muffler that is welded to the inlet pipe, instead of the torch you can use the exhaust pipe cutting tool and cut the pipe as close to the back of the muffler as you can get and skip the parts until it comes time to put on the new muffler. If you used the torch, turn it off and shut off the acetylene and oxygen tanks. Swap glasses again so you can see better.
4. Remove the muffler and any pipe and any hanger devices. Exhaust hanger removal tools are very handy, but you may not need them if the muffler is supported by a strap hanger that wraps around the muffler and supports it to the car frame. Get everything out of your way so you do not trip on anything while you’re looking up at your work area.
5. Clamp connection; If it’s a clamp connected pipe, use the exhaust pipe expander to try and work out the ridge indent the clamp made. Some of that might have been done when you were twisting off the muffler.
For the flange connection, clean the flange of all corrosion and rust using the gasket scraper. Be careful as it will be very hot. Tap the flange with the ballpeen hammer on the ball side and get as much rust off as possible.
6. To fix the clamp connection or if you cut the pipe with the pipe cutter, place the muffler inlet up to the inlet pipe connection and size the inlet of the muffler to see if it fits over the pipe snugly. You do not want a much larger inlet than the pipe you’re clamping it to or the other way around. You could use the pipe expander on the smallest side (muffler inlet or pipe) to bump it up a little and make the connection more snug. Rarely does a muffler inlet fit inside the pipe. It most always fits over.
To fix the flange connection, replace the gasket while holding the hop-over/under/intermediate pipe (the intermediate pipe will have hanger hooks that you can place into the rubber hangers to help you hold it while connecting the flanges) and have the nuts and bolts handy. Connect the flanges with the gasket between them, but do not tighten them all the way with the ratchet, socket and the extension with swivel (if you need them). Snug will suffice.
7. Install the muffler to the pipe and apply any support hangers or strap hangers. Paying attention to how the system fits inside its designed exhaust chamber, tighten up the system starting the furthest away from the muffler. So if it’s flange connected, tighten the flange first, then the clamp on the inlet pipe if applicable. Tighten the inlet clamp of the muffler, again making sure the muffler stays in it’s proper location. This will prevent any rattles or vibrations from the muffler hitting the frame or other nearby components. Tighten the tailpipe clamp if applicable. When everything is tight, hold the tailpipe of the muffler and give it a little shake to see if it hits on anything. Make any adjustments then.