Where there’s fire, there’s smoke. The controlled explosions within your car’s engine also produce “smoke,” or emissions. Your car’s exhaust system is supposed to remove these emissions from the engine and clean them up as much as possible before dumping them into the atmosphere. When your car’s exhaust system doesn’t do its job, you need to replace it. Components in your car’s exhaust system (illustrated next) include some or all of the following: exhaust manifold, exhaust pipe(s) and hanger(s), muffler, resonator, catalytic converter, and exhaust gas recirculation parts.
About replacing exhaust system components: Some can be replaced with simply a wrench, but others require welding equipment. Assuming that you probably don’t have an arc welder in your household (I could be wrong on this one), you can use clamps to cinch down joints between components. It’s doable. Working on your car’s exhaust system typically means getting it up on safety stands or ramps, blocking the wheels, and crawling underneath. Sorry, it can’t be helped.
Troubleshooting Tips for Tailpipes
In an effort to reduce noise and air pollution, here are a few tips for troubleshooting your car’s exhaust system:
- If your exhaust system is loud, the muffler might need replacement. If the noise sounds more like hissing, it’s probably a hole in an exhaust pipe.
- If the engine overheats or lacks power, the culprit might be a damaged muffler or tailpipe causing backpressure on the engine.
- If the exhaust system is noisy, visually inspect the pipes, muffler, catalytic converter, and other parts for obvious holes and broken hangers.
- If you can smell burning oil around the engine, the emissions-control system might be clogged and need cleaning or parts replacement.
The Manifold Life of an Exhaust System
The exhaust manifold collects burned exhaust gases as they leave the engine’s cylinders. The collected gases are then piped to the catalytic converter through the exhaust pipe. Cars with all cylinders in one row (2, 4, or 6) have one exhaust manifold. Cars with cylinders in a V-shape (V-6, V-8) have two exhaust manifolds. Exhaust manifolds are pretty simple in concept and construction. So what can go wrong with an exhaust manifold? Not a whole heck of a lot. It can become cracked or warped from excessive engine heat. Look and carefully feel for exhaust escaping from places it didn’t before. If exhaust is escaping, the exhaust manifold may need to be replaced, although there are some aftermarket products that claim to repair manifold cracks. More often, repairing an exhaust manifold means replacing the gasket seals between the manifold and the engine block or the manifold and the exhaust pipe(s).
To repair an exhaust manifold, follow these steps:
- When the engine is cold, locate the exhaust manifold on your car. The best way to do so may be backward: Find the exhaust muffler and pipe under the car and trace it into the engine compartment where it attaches to the exhaust manifold.
- If necessary, remove the bolts that connect the exhaust pipe(s) to the output of the exhaust manifold. You will need a long 1/2_ inch socket wrench driver to loosen the bolts. If they won’t budge, spray WD-40 or a penetrating lubricant on the nuts and let them sit for a while before trying again. After you have removed the bolts, check the gasket between the pipe and the manifold; if necessary, replace the gasket. Hold off on gasket replacement if you’re also going to remove the manifold.
- To remove the exhaust manifold, find and remove the bolts (or nuts) that attach the manifold to the engine block. There are typically two bolts per exhaust port or cylinder. Use a long liz-inch socket wrench driver to loosen the bolts or nuts. Carefully remove the exhaust manifold and gasket from the engine block.
- Replace the gasket and/or exhaust manifold if either is damaged, making sure that the old gasket material is removed from the engine and manifold. Then reinstall the exhaust pipe to the manifold output, replacing the gasket.
- Take a rest after your exhausting work.
Don’t Let Your Pipes Get Exhausted
Exhaust pipes are simply round pipes that transport exhaust gases from the manifold to the catalytic converter and/or muffler, but they aren’t pipes you can buy at a plumbing shop. Exhaust pipes are bent to fit specific cars. You can buy prebent exhaust pipes for most modern cars, or you can hire a muffler shop to bend the pipes. To repair an exhaust pipe that has a hole in it, purchase and use a muffler repair kit by following the package’s instructions. Most kits include a tape or adhesive that can temporarily plug the hole. Of course, don’t bother repairing a pipe that has numerous holes and really should be replaced.
To replace an exhaust pipe, follow these steps:
- If you are replacing the entire exhaust pipe, loosen and remove the bolts holding the exhaust pipe to the exhaust manifold, as described previously. If you are not replacing the entire pipe, loosen and remove clamps on the section(s) you will replace.
- Carefully loosen and remove hangers holding the exhaust pipe to the underside of the car, making sure that the unit doesn’t fall. You might need to grow or borrow an extra hand or two.
- Replace the exhaust pipe(s) and reconnect to the system. If you are also replacing the catalytic converter, muffler, and/or resonator, do so as you replace the pipes, starting at the exhaust manifold and working toward the back of the car.
- You deserve a treat for such a nice job. Sorry, I don’t have one for you, but you deserve it.
Let There Be Silence
A muffler minimizes exhaust gas noises. So what does a resonator do? The same thing. Some cars have both a muffler and a resonator in the exhaust system to reduce noise. Other cars can get by with just a muffler.
To repair or replace a muffler or resonator, follow these steps:
- Find and inspect the muffler/resonator for damage. A small puncture can be repaired using a muffler repair kit found at most auto parts stores. A rusty or damaged muffler/resonator should be replaced.
- To replace a muffler/resonator, figure out how the old one was installed: by welding or by clamping. If welded, the exhaust pipe may need to be cut with a hacksaw or replaced. If the muffler/ resonator’s joints are clamped together with metal connectors, remove the nuts holding the clamp in place and remove the muffler from the pipe. You might have to remove one or more hangers from the pipe to free the muffler or resonator. Replacement parts are available at larger auto parts retailers.
- Make sure all clamps and hangers are tight before test-driving your quiet car. You can now come in at 3 a.m. without waking all the neighbors.
TLC for an Aging Catalytic Converter
If your car was born in the past 20 years, it probably has a catalytic converter. There are two types: Older ones reduce carbon monoxide and hydrocarbons; newer ones reduce nitrogen oxides as well.
How long should a catalytic converter live? It should give you at least 50,000 miles of service and, with care, up to 100,000 miles.
If you suspect that the catalytic converter isn’t working well, take it to a mechanic who has emissions-testing equipment. If your converter needs replacement, do so yourself or have it done. Don’t even think about repairing a catalytic converter. Also, make sure your car hasn’t been operated in at least eight hours, allowing the catalytic converter to cool down completely.
To replace a catalytic converter, follow these steps:
- Find and inspect the catalytic converter. On most cars, it’s located between the exhaust manifold and the muffler or resonator. Inspect it for obvious damage or simple solutions such as a loose clamp. A piece of wood can be carefully banged on the casing to test it for rust.
- Remove the catalytic converter from the exhaust system. If the converter is welded, the exhaust pipe might need to be cut with a hacksaw or replaced. If your converter is clamped, remove the nuts holding the clamp in place and remove the catalytic converter from the pipe. You might have to remove one or more hangers from the pipe to free the catalytic converter. Larger auto parts retailers and dealer parts departments can get you a replacement catalytic converter if you tell them the car’s make, model, and engine size.
- Install the new catalytic converter, replacing rusty exhaust pipes and hangers as needed.
- Don’t forget that converted catalysts must also be confirmed.
Keeping the Environment Clean of Auto Emissions
Your car probably has at least 1.625 scads of emissions-control devices hidden in its nooks and crannies (see the next figure), maybe more. What do these components do? The exhaust gas recirculation (EGR) system returns exhaust gases to the engine for reburning. The positive crankcase ventilation (PCV) system recirculates gases from the oil pan to the intake manifold. The evaporative emissions control (EEC or EV AP) system recycles fuel vapors. It’s AC (Acronym City) under your car’s hood.
How can you repair these systems when they go awry? When you suspect-or have been warned by a state emissions control officer-that your car’s emissions-control system (ECS) isn’t working efficiently, you can test and replace it. Your car’s service manual or an aftermarket manual gives you specific instructions on how to test and replace these components. Here are some guidelines.
To replace an emissions-control component, follow these steps:
- Test the ECS components in your car using a vacuum gauge or volt-ohmmeter (VOM), depending on the component’s function. If it is a sensor, a VOM typically tells you whether it’s working correctly. If it recirculates fuel, oil, or emissionsvapors, a vacuum gauge can register vacuum pressure. Compare readings with those suggested by the manufacturer.
- Inspect the component for obvious damage. Then clean it up and test it again. Vacuum-operated components can be cleaned with a solvent. Electronic components can be wiped clean and retested, but cannot be rebuilt. Instructions in the service manual overrule anything said here.
- To replace a defective component, remove it from the car and take it (along with vehicle identification information) to your friendly auto parts professional. In most cases, the defective components are vacuum-controlled or electrically controlled valves that either work or don’t.
- Install the new part and test the system to make sure it works. Take your car to an emissions test center to verify that it works.
- Feel good about doing your part to keep the environment clean and healthy.