Loud engine-related noises after impact to exhaust system: any recommendations to pursue?

Question

1999 Toyota RAV4 took a big hit to the exhaust system (near the rear) yesterday on a logging road. Afterward, there was increased engine noise: I concluded immediately this was an exhaust leak induced by the impact. There is a tennis ball sized dent where the impact occurred, near the rear of the vehicle, but there is no leak there.

The added noise is coming from around front of the car. I felt around and found smoke puffing out at the joint between the exhaust manifold and the downpipe. I replaced the gasket in this joint and the puffing went away: the joint is now airtight. However, the noise only intensified.

It is difficult to identify the source of the noise. I don't feel any other puffing. I felt around the manifold gasket too, and all along the front exhaust system. The noise intensifies when the engine ramps up.

Any suggestion for an investigation or approach to repair would be appreciated!

Answer 1

If there is a tennis ball sized dent in the exhaust system then there are two possibilities. It may be that the dent is causing a restriction in the system which is causing pressure to build upstream of the dent. However, if the dent is in one of the expansion boxes or silencers, it may be that the baffles within this box have become dislodged or broken.

My suggestion for resolving this issue would be to replace the dented section of the exhaust and reassemble the whole system with assembly place ensuring that all of the hangers are intact. In either of the suggested scenarios, this would solve the issue.

Answer 2

I find the easiest way to find exhaust leaks is to have someone else blow compressed air into the tail pipe when the vehicle is cold and not running. Doing it this way allows me to not only hear, but also feel for air leaks without burning my hands.