A damaged exhaust manifold can be exhausting to your ears. Four-cylinder engines with exhaust leaks can be especially obnoxious — they tend to produce a high-pitched drone that some people find as abrasive as the sound of nails on a chalkboard. Furthermore, exhaust manifold leaks can cause poisonous carbon monoxide gases to leak into the interior of your car. To protect your eardrums and your health, you need to diagnose and repair exhaust manifold leaks as soon as they occur.
Locate the Exhaust Manifold
Four-cylinder engines are laid out with the intake system on one side of the block and the exhaust system on the opposite side. Even if you're not familiar with exhaust systems, locating the manifold isn't difficult — it consists of four metal tubes welded to a flange that's bolted directly to the engine block.
Make sure your engine has cooled off entirely, then pop your truck's hood. A lot of modern engines have plastic covers on top that hide the intake system and exhaust manifold. However, they are generally only held on by a few easy-to-find screws or bolts around the edge of the cover. Remove all of the screws or bolts and the engine cover will lift right off.
Additionally, some trucks have a metal heat shield bolted over top of the exhaust manifold. Remove all of the bolts holding the heat shield in place and lift it off to reveal the exhaust manifold.
Inspect the Welds for Cracks
Get a bright flashlight so you can see the exhaust manifold as clearly as possible. The most likely culprits for leaks are the welds that connect the exhaust tubing to the manifold flange — they're prone to cracking over time due to heat stress and engine vibration. Having a small mirror such as a dental mirror will make the inspection process easier because it will allow you to easily see the welds hidden on the bottom of the piping.
Closely inspect all of the welds for any signs of cracking — even hairline fractures can allow exhaust fumes to escape. Some exhaust manifolds also have welds that connect different sections of the piping together. Shine your flashlight down the tubing and inspect any welds you find with the same scrutiny.
If you find any cracks, the exhaust manifold needs to be repaired or replaced immediately. Depending on the severity of the damage, an auto repair shop may be able to weld over the cracked areas and keep your stock manifold intact. However, if the cracks are too severe, you'll have to replace the manifold with a new unit.
Inspect the Exhaust Gaskets
Exhaust manifold gaskets are another common culprit for leaks. The gaskets are generally made of a rubber compound in order to create airtight seals between metal surfaces. Because your exhaust system gets so hot, the gaskets can melt and wear out over time. Worn gaskets allow exhaust gases to escape and make your truck's engine sound louder.
Closely examine the surface of the engine block around the edge of the exhaust manifold flange. If a section of the gasket has worn through, there will likely be soot and residue stuck to your engine around the area where the exhaust leak is occurring.
Some trucks have multi-piece manifolds with an exhaust collector section on top and a tubular section bolted beneath it. If that's the case with your truck, there will also be a gasket between the separate sections of your manifold. Examine the manifold piping around the flange that connects the separate sections for buildups of soot or residue.
You can also use baby powder to check for gasket leaks. Sprinkle baby powder along the edge of each gasket flange, then press into the flange gaps as tightly as possible. Have someone start your truck while you're still shining your flashlight onto the exhaust flanges. If there are any leaks, the escaping gases will blow the baby powder into the air. Replace any faulty gaskets as soon as you discover them.
Nobody likes putting up with excessive exhaust noise and smells while they're driving. Luckily, you don't have to be a professional mechanic to inspect your truck's exhaust manifold. Repairing your exhaust manifold and gaskets is relatively cheap and easy. More importantly, it'll help ensure the comfort and safety of you and your passengers.
If you need to replace your exhaust manifold, contact a company that sells truck parts.