How to Identify Car Exhaust Issues

close up of tailpipe

The exhaust system on your vehicle is probably more significant than you would think. Besides reducing the noise created by your engine, the exhaust system directs harmful gases away from the cabin, helps cool down the engine, and most importantly, cleans the air before exiting the tailpipe. Identifying exhaust issues early on will keep you safe and keep your wallet full.

Carbon monoxide is a colorless, odorless gas that is present in exhaust fumes. Inhaling carbon monoxide, even in small doses, can be very harmful to your health. It can cause headaches and dizziness, and in extreme cases can lead to unconsciousness. Obviously, if this is the case, then you should take the car in to get inspected and repaired as soon as possible.

Part 1 of 2: Identify exhaust issues

Step 1: Listen for odd sounds. The muffler is full of baffles and if these break or fail, the sound of the engine won’t be dampened quite as much.

Any rattling or thumping is not normal either. Some vehicles have baffles that can open and close to make the car louder or quieter. Over time the linkages that hold the door can break or become loose causing a rattling noise.

Rattling sounds can come from a few places. As catalytic converters start to age, the interior will begin to degrade and all the small pieces will rattle around as you drive. This same thing can happen with the baffles inside the muffler.

A heavier thump typically indicates the mounting may be loose or damaged. The exhaust system is held up with metal and rubber brackets. Over time the rubber gets brittle and falls apart.

Identifying this early is very important because it can mean the difference between replacing a small piece of rubber or a whole piece of exhaust. If the mount fails, the exhaust pipes can fall or rattle around and dent while you are driving.

Step 2: Use your nose. While carbon monoxide is odorless, the other gases coming out of the tailpipe aren’t.

If you notice any exhaust smell in the cabin, there is probably a leak somewhere. As mentioned, the carbon monoxide in the exhaust fumes can be very harmful.

Step 3: Look for signs while driving the car. There are a few things you can look for while driving the vehicle.

Loss of performance and reduced gas mileage are common with blocked off exhausts. If the engine has to work harder pushing the exhaust out of the cylinder, it has less power to give to the wheels.

A blocked off exhaust can also cause the car to run hotter than normal. Exhaust gas is very hot as it leaves the cylinder and any blockage will restrict the airflow, keeping the heat closer to the engine.

Part 2 of 2: Visual inspection under the car

Materials Needed

exhaust manifold under hood

Step 1: Lift hood and inspect exhaust manifold. The exhaust system starts as soon as the air leaves the cylinder.

On the side of the engine block there will be pipes running out, connecting together, and then heading to the bottom and back of the vehicle. You may not be able to see much, but inspect what you can see; we’ll get to the rest later.

Check and make sure all the bolts are not loose and are still there. These can fall out over time from the engine vibrations.

Look for cracks in the metal. Due to the heating and cooling over the life of the vehicle, the metal can develop cracks.

  • Warning: If the engine was on recently, these will be hot, so take care if you are poking your hand around checking bolts.

car lifted on jack stands

Step 2: Lift the car and set on jack stands. On a flat level surface, lift the vehicle with your jack.

Place jack stands at all corners to make sure the car won’t fall while you are underneath.

mechanic inspecting underneath the engine

Step 3: Inspect the bottom of the exhaust manifold. You should be able to see parts of the manifold that you couldn’t before, so inspect the rest for similar issues.

cc being inspected

Step 4: Inspect the catalytic converter(s). Tap the converter lightly with a rubber mallet or the end of a screwdriver and listen for anything rattling inside.

Over time the interior of the catalytic converter can start degrading and the pieces will rattle inside as you drive. Check the connections going into and out of the converter to make sure they are intact. Any dents or dings, however small, will create a gap for gas to escape.

The converter itself shouldn’t have any external damage. Dents on the outside generally lead to damage on the inside and the whole unit would need to be replaced as a result.

  • Note: Some catalytic converters have a heat shield to keep the converter at the correct operating temperature. Make sure the shield doesn’t touch the converter as this can lead to a rattling sound from the vibrations. Ensure the shield is secured properly as well. A loose or missing bolt can cause it to create rattling noise while driving.

person inspecting a muffler

Step 5: Inspect the muffler(s). Check the muffler like you did the catalytic converter.

Dents on the muffler or the connections can cause issues with airflow. The muffler tends to be more susceptible to rust damage as moisture can build up inside. Surface rust is normal, but if it penetrates through the metal, you can be sure there is more rust on the inside.

x pipe on the underside of vehicle

Step 6: Inspect other connections and pipes. Check the rest of the pipes for cracks, dents, or excessive rust.

V-style engines and dual exhaust systems tend to have an X, Y, or H connection. Check all the seals for dents. The piping should not contact any other metal. This helps keep the metal cool and keeps the heat from transferring to other parts of the car.

Step 7: Inspect the exhaust mounts. As mentioned, the mounts for the exhaust system tend to use a rubber loop to hold the pipes in place and allow for some movement.

Check to make sure the rubber isn’t falling apart and that it is installed correctly. Test the mounts by shaking the muffler. There should be a little play to allow for knocks and bumps, but too much and the piping can hit other components.

With these steps, you can identify any exhaust issues that you are experiencing. The key with many of these problems is identifying them early on before any serious damage occurs. You can avoid a hefty repair bill by being proactive with your vehicle and identifying small issues before they become a big problem. If you require any help identifying issues with your exhaust, our certified technicians here at YourMechanic would be glad to perform a system inspection.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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