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Exhaust Leak Questions

A. If there's a burning aroma lingering in your cabin (and you didn't just drive by a smokestack) Exhaust Leak service should go right to the top of your To-Do list. Behind those yucky fumes you smell, more poisonous gasses may be sneaking into your cabin -- that you can't smell.

Since you can't always smell an exhaust leak, pay attention to any changes in your vehicle's acceleration performance. Book an appointment at the first sign of sluggish pickup, backfiring, funny noises, or a vibrating gas pedal. (Better yet: have your exhaust system checked regularly at Midas.)

A. An exhaust leak is a hole (or other defect) in your vehicle's exhaust system that lets toxic exhaust fumes enter your cabin instead of exiting your vehicle through the tailpipe. Engine exhaust contains poisonous gasses like carbon monoxide, nitrogen oxides, phosphorus, metals such as lead, and unburned fuel (hydrocarbons). An exhaust leak can endanger you and your passengers if the fumes build up in your cabin faster than your car's ventilation system can evacuate them. Exhaust leaks can also compromise your vehicle's fuel efficiency and performance, make your ride noisier, and damage your catalytic converter.

A leak can develop anywhere along the parts of a vehicle exhaust system:

  • Exhaust valve and piston: Engine parts that force exhaust fumes out from the combustion chamber (where they are created) to the exhaust manifold.
  • Exhaust manifold: The path from the piston to the catalytic converter.
  • Catalytic converter: Converts some toxins to carbon dioxide (CO2) and water for cleaner emissions -- though the exhaust is still poisonous in confined spaces (and CO2 is a greenhouse gas).
  • Exhaust pipe: Carries the cleaner exhaust gasses to the muffler.
  • Muffler: Reduces the noise of combustion and expulsion of exhaust.
  • Tailpipe: Where exhaust leaves your vehicle.

A. The most common signs of an exhaust leak are bad smells, unusual smoke, engine noise, and visible damage to your muffler or tailpipe. Other things to look for:

  • Your Check Engine light is on. In many modern vehicles, a problem with emissions or exhaust will trigger the Check engine light.
  • Gasoline, burning, or rotten egg odor in the cabin. Any troubling smells (that can't be explained by the air you're driving through) should be diagnosed immediately. If the fumes you can smell are in your cabin -- so are the carbon monoxide or carbon dioxide you can't smell.
  • Black smoke from your tailpipe. Your exhaust manifold could be blocked, among other issues.
  • Hissing, Popping, Tapping, or Ticking Noise. Donut gasket and manifold leaks are the prime suspects when you hear this sound, especially during acceleration or a cold start.
  • Vehicle performance problems. Exhaust leaks are one of many obstacles to fuel efficiency, engine power, and acceleration performance. Some leaks cause the gas pedal to vibrate during acceleration, or even backfiring along with sluggish acceleration.
  • Hanging or dragging tailpipe. Somewhere along your exhaust system, a pipe is broken or bent, or your muffler or tailpipe is no longer held in place. This situation will probably cause a leak if one doesn't already exist. Your Midas technician can determine whether you need exhaust leak service or muffler service.

A. People describe the sound of an exhaust leak in different ways: Ticking, tapping (sometimes "fingernail tapping"), popping, or ticking like a clock. The classic exhaust leak sound is a rapid ticking effect while accelerating or starting cold. The exact sound depends on where the exhaust leak is, and where you're sitting in the vehicle when you hear it.

Any new noise from your vehicle should be diagnosed by a qualified mechanic. And at Midas, we've heard everything -- so request an appointment today.

A. For your safety and the safety of your passengers, drive as little as possible if you suspect an exhaust leak. You already know that vehicle exhaust can be lethal in a confined space such as a closed garage. An exhaust leak that sends enough carbon monoxide (CO) into your cabin can make you an unsafe driver. According to engineer T.H. Grenier, "Studies show that elevated CO in the body interferes with driving skills. At high carbon monoxide concentrations CO intoxication occurs and severely impairs driving ability. People suffering from CO intoxication think slowly and irrationally, are confused, and are unable to safely operate a motor vehicle."1 And it's not just your driving that suffers. Sustained exposure to low levels of CO poses serious health risks. According to Harvard Medical School, symptoms of low-level CO exposure (over weeks or months) include flu-like symptoms, nausea, vision problems, numbness, sleep disturbances, and impaired concentration and memory.2

  1. Carbon Monoxide Poisoning: What Is It? from Harvard Medical Publishing, June 2019.

A. One way an exhaust leak can negatively affect your gas mileage is by causing falsely low readings in your oxygen sensor. The sensor responds to the perceived shortfall by increasing fuel consumption. In many vehicles, the Check Engine light will eventually flag the overconsumption of fuel. This effect only applies to gasoline vehicles, typically in leaks before the catalytic converter.

A. One way an exhaust leak can compromise engine performance is by sending exhaust back into the combustion chamber -- decreasing the space available for new fuel to be burned. You may notice a lower level of engine power in general, and noticeably sluggish acceleration.

A. To help prevent carbon monoxide poisoning, the Centers for Disease Control and Prevention (CDC) recommend having your exhaust system professionally checked at least once a year.3 Between full exhaust system checks, Midas performs a visual inspection of your exhaust system as part of every Midas Touch Courtesy Check.4

  1. Midas Touch Courtesy Check includes visual checks of brakes, battery, air filter, fluids, belts, and hoses.

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