How to Find and Fix an Exhaust Leak

Exhaust Leak Symptoms

Your engine sound changes. The most obvious sign of an exhaust leak is a change in engine sound. You might hear hissing, popping, or metallic rattling—especially when accelerating. Or the exhaust sound might be noticeably louder. Take a drive with the windows down and listen.

Your gas mileage drops. Your engine is tuned based on gasses leaving correctly through designated pathways, so you might identify a leak if you notice a decrease in gas mileage. If you are making more frequent trips to the gas station, that could be a sign of an exhaust leak.

You smell a leak. If you smell exhaust fumes, check for visible signs of a leaky exhaust. Look under the car and follow the path of the exhaust system. If you notice obvious gaps or holes, engine exhaust might be escaping.

Your check engine light comes on. Newer cars with catalytic converters, O2 sensors, and other electronics will often register a code in the car’s computer and illuminate the dreaded check engine light. A code reader might steer you toward the exhaust system.

Read this: What Does the Check Engine Light Mean?

Causes of Exhaust Leaks

In lieu of welding, you can use connectors to join exhaust pieces.

Exhaust leaks can occur for several reasons. For example, a tubing joint may come apart within the system. The exhaust piping relies on hangers to hold it securely in place, so if a hanger fails, the exhaust tubes create more stress on the joints, resulting in a leak.

Another common cause is running over an object or hitting a pothole, which could damage the system. Salted winter roads can also corrode metal, and as cars age, parts start to fail. All of these factors could lead to an exhaust leak.

A braided connector provides a leak-free connection with flexibility.

How to Find an Exhaust Leak

If you suspect an exhaust leak, start the vehicle and try to hear and see the source of the leak. You might see black carbon deposits near the exhaust leak. Then, use your hands to feel for an exhaust leak—but act quickly before the metal parts get warm.

Exhaust hangers

Next, fill a spray bottle with a mixture of one part kitchen soap to 10 parts water. Spray the solution near where you suspect a leak. If bubbles appear, you’ve found the leak. Perform this soapy-water test when the engine and exhaust parts are cold to avoid creating steam.

If you can’t pinpoint the leak with the soap solution, use a shop rag to block the tailpipe temporarily. This will create more pressure in the exhaust system, making it easier to detect the leak. If you can safely reach under the car, gently wiggle the exhaust tubing to see if any components are loose. Don’t leave the rag in place very long, as this can choke the engine and cause other problems.

DIY Repair

A turndown tip directs exhaust gasses to the road.

There are a few relatively simple tasks to to address the leaks. Start with these:

• If the exhaust gasket used to seal the metal pieces of your exhaust system has rotted, it could create a leak. Try unbolting the two components. You might need to spray the bolts with penetrating fluid and soak them overnight to make them easier to remove. Replace the gasket and bolt everything back together to see if it eliminates the leak.
• If the hangers holding the pipes have come loose, you should replace them to prevent the exhaust piping from rattling, sagging, and leaking.
• If a section of exhaust piping has corroded and failed, it’s time to install replacement pieces. That process can be easy when the tube is short and straight, but curved segments are more complicated.

Leaks caused by catalytic converter or muffler problems may be best fixed with a visit to a professional repair shop unless you have the necessary welding skills.

You might be tempted to try a short-term solution, such as covering leaks with metallic tape or an epoxy bond, but that may only last a few days or weeks. Remember, a leaky exhaust wastes fuel and is dangerous. If you detect a leak, complete the repair as soon as possible.