Why does exhaust get more loud with age?

[Seymore Butts]

I noticed that my '08 v6 as well as many other T4Rs of similar age are not as quiet under acceleration as they used to be. Specifically, when I hear my engine sound reflected from nearby objects such as walls or concrete lane dividers, I can hear a certain engine rumble that reminds of the way very old buses sound. However, not nearly as loud, of course. This happens only when I accelerate from a stop. At idle, the engine is impressively quiet.

What is the cause of this sound? Loosened exhaust manifold bolts, tiny holes, cracked exhaust manifold, head gasket failure, or something else?

 

[oljedi11950]

Check heat shields by y-pipe area !

 

[LexsCTJill]

I noticed that my '08 v6 as well as many other T4Rs of similar age are not as quiet under acceleration as they used to be. Specifically, when I hear my engine sound reflected from nearby objects such as walls or concrete lane dividers, I can hear a certain engine rumble that reminds of the way very old buses sound. However, not nearly as loud, of course. This happens only when I accelerate from a stop. At idle, the engine is impressively quiet.

What is the cause of this sound? Loosened exhaust manifold bolts, tiny holes, cracked exhaust manifold, head gasket failure, or something else?

Did you ever get to the bottom of this? My 4Runner seems to get louder and louder lately.

 

[mjotrainbrain]

Did you ever get to the bottom of this? My 4Runner seems to get louder and louder lately.

Have you inspected the exhaust? Could have rust holes, or parts have dropped off completely due to rust.

 

[T4R2014]

The corrosion from moisture and salt + vibrations over the years adds up. Two of my third gens sound like piles of shit. Meanwhile the one with a new exhaust from cat to tailpipe sounds like it's 1996. The difference is incredible.

 

[Keros]

Most mufflers contain sound deadening material sandwiched between baffle plates that create corridors that force exhaust gas to take a confusing route through the maze of plates so that the noise can be absorbed by the sound deadening material.

The material, being fiberglass or stainless steel matting for example, degrades over time as its exposed to the heat and moisture from the exhaust.

Even the baffle plates themselves can rust out, leaving the muffler to just be a big hollow shell.

It's kind of a sacrificial component.

 

[LexsCTJill]

Have you inspected the exhaust? Could have rust holes, or parts have dropped off completely due to rust.

Appears my cat is starting to fail. I now have a CEL light on.