An exhaust leak is a hole or crack in your car's exhaust system, which allows toxic gases like carbon monoxide to escape before they reach the tailpipe. This isn't just a noise issue; it's a serious safety and performance problem that requires immediate attention. The most significant danger is the potential for carbon monoxide, an odorless and deadly gas, to enter the passenger cabin.
The symptoms are often unmistakable. You'll typically hear a loud rumbling or tapping sound that gets louder when you accelerate. There might be a distinct smell of sulfur or rotten eggs from the engine bay, and you could feel a loss of engine power and fuel efficiency because the backpressure needed for the engine to run optimally is lost.
Common causes include rust (especially in colder climates where road salt is used), damaged gaskets where exhaust components connect (like the exhaust manifold gasket), or cracks from impact with road debris. To confirm a leak, a mechanic will often perform a smoke test, where smoke is pumped into the exhaust system to visually identify escape points. Ignoring a leak can lead to failed emissions tests, damage to oxygen sensors and the catalytic converter, and health risks. The fix usually involves replacing the damaged section, which can range from an inexpensive patch for a small hole to a costly replacement of the catalytic converter.
| Exhaust Leak Symptom | Potential Cause & Location | Estimated Repair Cost Range (USD) |
|---|
| Loud rumbling noise near engine | Cracked exhaust manifold or broken manifold gasket | $150 - $1,000+ |
| Ticking sound on cold start that may quieten as engine warms | Blown exhaust manifold gasket | $200 - $600 |
| Hissing sound underneath car | Pinhole leak in muffler or pipe | $100 - $400 |
| Rotten egg smell | Leak near catalytic converter | $150 - $2,000+ (if converter replacement is needed) |
| Decreased fuel economy & power | Leak upstream of oxygen sensors, causing faulty readings | Varies by leak location |
| Visible black soot around a joint | Failed gasket or loose clamp | $50 - $300 |
