What Is an Exhaust System?
A car’s exhaust system is an interconnected assembly of pipes, connectors, sensors, and mechanical devices that is designed to handle and dispose of exhaust fumes that result from the engine’s combustion process.
What Does an Exhaust System Do?
An exhaust system’s three primary functions are:
*Funnel exhaust gases away from the driver and passengers.
*Quiet the noise created by the internal combustion process inside the engine.
*"Clean" the exhaust fumes of gases that are harmful to humans and to the environment.
Exhaust leaks can be extremely loud and annoying.
Anatomy of an Exhaust System
Most of these parts are made of steel and designed to handle the stresses of living underneath a car. We’ll go from the closest to the engine to the rear of the vehicle for easier understanding.
The exhaust manifold is bolted to the engine. It collects the exhaust gases from the cylinders and funnels them into one output tube.
A catalytic converter cleans the exhaust gases, in a way, by reducing harmful fumes exiting the engine. Using catalysts, it converts hydrocarbons, carbon monoxide, and nitrous oxides into byproducts such as water vapor, carbon dioxide, and nitrogen.
A resonator is like an echo chamber that is designed to change the tune of the engine as the exhaust gases flow through.
A muffler helps to mute the loud noise the engine creates.
The tailpipe is the final pipe that releases the exhaust gases into the air we breathe.
Connecting pipes are located between the several parts of the exhaust system and come in a variety of shapes and sizes.
Oxygen sensors inform the ECU to help make sure the air/fuel mixture is correct.
Symptoms of an Exhaust Leak
There are several tells you have an exhaust leak. Look out for these symptoms:
If there’s a hole in the exhaust, it might make driving, accelerating in particular, loud. Like, really loud. You’ll know.
Buzzing, Hissing, Ticking, Popping, Puffing Noises
Depending on where the leak is, how big the leak is, and what shape the hole is, a leak can make all sorts of noises and sound all types of ways. It will sound louder outside the car and will likely change frequencies or get louder if you rev the engine.
If air is escaping through a crack, bad gasket, or hole, it could cause unwanted metal vibrations.
Worse Gas Mileage
Depending on where the leak is, it might skip or avoid oxygen sensors that are essential to optimal combustion. If the oxygen sensor cannot provide an accurate reading, the ECU might tell the car to use more fuel, which will hurt your fuel economy.
Exhaust Fumes in Front of Car or Cabin of Car
One of the exhaust system’s functions is to make sure you aren’t breathing in exhaust fumes. If you start to smell exhaust at the front of the vehicle near the engine or inside your actual cabin, you have a problem.
Exterior Carbon Buildup
When you’re searching for the source and location of the leak, keep an eye out for black spots. If exhaust is escaping, carbon particles might build up around the leak.
Literal Holes in the Metal
Sometimes a chunk of metal is missing from your exhaust system, it happens. We’d bet a dozen Munster Donuts that’s the source.
If you can get your car on a lift, it'll be easier to inspect.
Causes of an Exhaust Leak
Your exhaust system could spring a leak for many reasons, such as:
Your exhaust spends its entire life staring at the ground. It gets hot, it gets cold, it faces rain and snow, it’s buck-shot with gravel, it’s sprayed with road tar, and it bathes in other car’s leaked oil. Stainless steel can take a lot, but eventually, your exhaust is vulnerable to corrosion.
Your exhaust is under the car, and not everybody drives on perfectly smooth pavement. Potholes, or other road hazards, could cause damage to the low-hanging exhaust system. It also might get hit with rogue road debris.
Gaskets, such as the ones found between the manifold and the engine, can degrade over time and create uneven surfaces that allow for leaks.
If somebody previously repaired the exhaust and did a poor job, it could result in new leaks.
Time and Age
Everything fails eventually. Sometimes your exhaust has put in the work and needs to call it quits.
Our Tips For Finding Exhaust Leaks
Finding exhaust leaks can be tricky, but there are a few methods to simplify the job. Try these tips.
Listen and Feel
Once your car is completely cooled down, turn it on, listen for the leak, and run your hand along, but not on, the system to feel for air coming out. Start from the front of the vehicle and work your way back. Using a friend to occasionally rev the engine can help.
Block the Exhaust With a Rag
If the initial check doesn’t work, blocking the tailpipe with a rag can help exaggerate the leak. Let the car cool down again, insert the rag to block most of the air, then start the car and search for the leak once again. Because the air cannot escape from the tailpipe as easily, it might try to use the leak for an easier way out. This could force more air out of the leak, which makes it easier to find.
If you still can’t find it, there’s another toolless method you can try. After letting the car cool down completely, spray possible problem areas with a mixture of soap and water. When you turn the car back on, the air coming out of the leak should theoretically blow bubbles or foam up.
If you can afford it, automotive smoke machines do exist. Send the smoke through the exhaust system, and it will exit through the leak.
Shop-Vac Into the Exhaust Pipe
Opinions differ on this popular method, as some believe it could potentially be harmful to your car.
First, take a cleaned-out Shop-Vac and switch the suction tube to the blower hole to create a reverse effect. Attach that hose to the tailpipe and create pressure within the exhaust system. This should theoretically exaggerate the leak, which makes it easier to find.
The worry is that air is not meant to be blown the opposite way through an exhaust system, and it could blow contaminants back up into your engine.
Improper welds from past repairs could lead to leaks.
Fixes for Exhaust Leaks
Unfortunately, exhaust work tends to be left to the professionals, as many of the issues are related to metal corrosion and require replacement, which requires welding. In some cases, however, you might be able to get away with replacing bolt-on parts or gaskets. Budget-friendly suggestions might include sealants, tapes, and putties, but those are only temporary fixes that will eventually need to be addressed at a later time.
Get Mobile Automotive Service and Repair with YourMechanic
While The Drive’s how-to guides are detailed and easy to follow, no vehicle is created the same, and not all auto maintenance or repair tasks are easy to accomplish on your own. That’s why we’ve partnered with YourMechanic and their network of mobile automotive technicians to offer our readers $10 off a $70 or more service call when you use promo code THEDRIVE.
Excerpt from AEGEUS