8/02/2005

Eliminating harmonic noise

Sometimes as you drive, your vehicle will start making noises. It's unavoidable on these older Benz's, but the noise is still annoying. You've got a problem if an engine is making a noise. If it's some other part on your car, it could be fun playing a little detective and investigating. My car recently started to make a weird low-frequency murmur on low RPMs. Normally, these diesels are pretty quiet when you are going slow through town (at least from the inside). However, I could hear a distinct low freq. "b-o-o-r-r-o-o-o-r-r-r-o-o-o" from somewhere in the back. After driving like that for a couple of weeks, I started to get increasingly more pissed off, and decided to look for the source of the noise. I know it was coming from the back on low RPMs, but not when idling. I asked my wife to come out and give it some gas. When the noise appeared, I rolled under the car and listened in. As I was lying on my back, I noticed how worn the rear muffler hangers were. Those are just 2 thick rubber rings on which the rear part of the exaust hangs: The rings were extremely rotten. I am surprised the muffler didn't just fall off during my commutes. Under the rings I spotted some metal ... some industrious fella hung the muffler on wire! I had a couple of spare muffler hangers because I like to stockpile gaskets and rubber parts for my Benz. I dove under the car again, cut the wire, and threw out the rotten rubber hangers. I proceeded to replace them with my brand new hangers, which was kind of a chore. The rings are perfectly round, and they don't want to go on the muffler hooks without some serious stretching with a screwdriver. Hang the one closer to the rear driver's side wheel first ... ... then hang the other one. For some reason, the hooks on driver's side are a bit deeper. When you're done, you'll see how the muffler spreads the distance between the hooks ... right down the middle.