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Exhaust leaks can be one of the most annoying car ailments, especially considering the car still runs and drives, but generally sounds awful from inside the cabin. The exhaust manifold starts this journey of exhaust gases, and they can be prone to cracking and leaking. 

An exhaust manifold leak can allow toxic engine exhaust into the cabin of your vehicle and also reduce your vehicle’s efficiency. Exhaust is composted of carbon monoxide gas and is odorless and colorless, and extremely dangerous to you and your passengers. A leaking manifold is also dangerous for your engine over a longer period of time, as it can cause a burned exhaust valve, leading to a loss of engine compression and power. 

You can hear a leaking exhaust manifold really well. The sound will come from the engine area, not from under the car and has a distinct loud ticking or snapping sound. This sound can often be mistaken for lifter noise or an engine knock, so it’s best to rule out an exhaust manifold issue first.

Exhaust manifolds can run anywhere from $80.00 and up to and over $500.00 to replace the part, depending on the complexity of its construction. On some vehicles, the manifolds are relatively easy to change, and other vehicles can require multiple steps and hours to remove, making the total replacement cost have an incredibly wide margin. Some vehicles now have the Catalytic Converter built directly into the exhaust manifold, furthering the cost.

It’s important to understand the ways an exhaust manifold can fail, and more importantly, address it immediately. If you need help with this job, search any one of our Preferred Shops in your area to help you complete the job.

How an Exhaust Manifold Can Fail

1

Gaskets

An exhaust manifold is bolted to the engine via a series of bolts or studs / nuts. This is sealed by a gasket made of high temperature material and metal. At the other end, an exhaust pipe or catalytic converter attaches to the manifold via a flange or donut gasket. On a turbocharged engine, the turbo is normally mounted directly to the exhaust manifold. Any of these gaskets can fail, creating a large exhaust leak right at the manifold. The good news here is that usually the manifold is OK – a gasket replacement will remedy the exhaust leak.

2

Broken Mounting Studs

Most exhaust manifolds are attached with mounting studs. Many of these studs also hold down other accessory brackets in and around the engine and are secured on the exhaust manifold with nuts. When removing these nuts, many times, the studs can break. Because it can be a vary labor intensive job to remove and replace broken studs, these missing fasteners are often left broken, which can then lead to a weak point in the gasket, and gasket failure. Broken mounting studs can also force the exhaust manifold’s surface to warp, leading to cracks.

3

Cracked Manifold

Most exhaust manifolds are made out of cast iron, which is an excellent material to handle the constant heat expansion of getting hot and cold. Over time, however, cast iron is prone to crack, leading to an exhaust leak. Flanges can also crack or completely break off, specially at weld joints. In both cases, a manifold replacement is usually needed.

In any cases of exhaust manifold failure, it’s imperative to fix or remedy the issue as soon as possible, not to mention driving a noisy and unsafe car is never fun. Get your car into a shop to have a full exhaust inspection, or don’t hesitate to come into your local AutoZone, where we will have all the parts you’ll need to tackle the job yourself if you choose to do so.

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Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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