Do I Really Need to Have that Exhaust Leak Fixed?

By Karen Johnston May 19, 2011

Quick facts

Carbon monoxide is odorless and colorless. You cannot detect it without a sensor.
Exhaust gases include carbon monoxide, carbon dioxide, nitrogen oxides, and hydrocarbons.
An exhaust leak upstream of the catalytic converter bypasses its emissions-reducing function.
Louder exhaust sound and popping or ticking noises are the most common early signs of a leak.

The exhaust system of your vehicle plays an important part in the proper operation of the vehicle. Vehicles create harmful gases during the combustion of fuel that happens when the engine is running. The exhaust system is used to expel those gases from the car, and to control the emissions that come out of the vehicle. The exhaust system also deadens the sound that is made by the internal combustion of the engine. It is important to keep a close eye on your exhaust system and to have it fixed if a leak is detected.

The exhaust gases of a vehicle are made up of hydrocarbons (unburned fuel), carbon dioxide, sulfur dioxide, carbon monoxide, nitrogen oxides, phosphorus, lead and other metals. These poisonous gases can be hazardous if they leak into the cabin of the vehicle. Having them properly exiting the vehicle through the exhaust, via the exhaust manifold, exhaust pipe, catalytic converter, muffler and tailpipe, which gets them away from the cabin of the vehicle.

The catalytic converter helps to turn these gases into mostly harmless fumes that do much less damage to the environment. Routine inspections of the exhaust system are recommended. Your trusted repair facility should be looking for worn, rusted or deteriorating exhaust pipes, mufflers and catalytic converters. Some of the symptoms to look and listen for are: increased exhaust or engine sounds that are louder while running the vehicle, popping or ticking noises especially when cold, gas or rotten egg smells inside the cabin of the vehicle, and sometimes a lack of power or backfiring while accelerating.

If you are experiencing any of these symptoms, we recommend having that exhaust system checked out. Whenever you are advised of an exhaust repair that is needed, we highly recommend having that repair performed. The most harmful gases from exhaust are the ones that you cannot smell, like carbon monoxide, so that routine inspection of your exhaust system is very important. Keep that exhaust system in proper repair for your health, the health of your family and the health of the environment.

Frequently asked questions

Common questions

Where are exhaust leaks most likely to develop?

The exhaust manifold gasket is the most common failure point, particularly on high-mileage engines where repeated heat cycles cause the gasket to compress and crack. Flex pipes, the corrugated sections designed to allow movement, also deteriorate and crack with age. Muffler and resonator seams rust from the inside out due to condensation, and clamp connections can loosen over time.

Can an exhaust leak cause a failed emissions test even if the engine is running well?

Yes. An exhaust leak upstream of the downstream oxygen sensor fools the engine computer into misreading the exhaust composition. The resulting fuel trim adjustments can cause emissions to climb even if the engine and catalytic converter are otherwise in good condition. An exhaust leak should be repaired before attempting a DEQ test if there is any doubt about its location.

Is a rotten egg smell from the exhaust an exhaust leak or a different problem?

A sulfur or rotten egg smell coming from the exhaust vents usually points to a failing catalytic converter rather than an exhaust leak. The converter contains precious metal catalysts that convert hydrogen sulfide in fuel into odorless sulfur dioxide. When the substrate degrades, conversion efficiency drops and the smell appears. An exhaust leak that routes gases into the cabin is more likely to smell like burned metal or raw exhaust.

Schedule service

All About Automotive — 1850 NW Burnside Rd, Gresham, OR · (503) 465-2926

Book an appointment Browse services More articles