Exhaust Manifold / Catalytic Converter

Frequently Asked Questions

An exhaust manifold is a component of the exhaust system consisting of a collection of cast iron tubes capable of withstanding the high exhaust temperatures. The manifolds have short inlets, which can be of varying lengths, that converge into a single collector. Engines with a "V" or flat configuration have two manifolds, while inline or straight engines have only one manifold. And it can collect the exhaust gases produced by an internal combustion engine and direct them to the catalytic converter or turbocharger. In addition, exhaust manifolds protect occupants from dangerous gases by carrying the exhaust gases from the combustion chamber to the exhaust pipe, where they are safely vented to the outside of the vehicle. It is therefore considered part of the "lungs" of an engine.

Step 1: Collect the air mixture from each cylinder. The manifold itself must be designed to collect as much exhaust as possible from each cylinder.

Step 2: Concentrate the heat of the gases. It completely burns any unused or incompletely burned gases with its very high temperature.

Step 3: Check the oxygen level in the exhaust. The manifold also houses the oxygen sensor to check the amount of oxygen entering the exhaust system.

Step 4: Send to the fuel injection system to increase or decrease the amount of oxygen used in the air mixture to power the engine.

Step 5: Eject the collected gases to the rest of the exhaust system.

Step 6: Acts as a funnel, using exhaust pressure to push gases out with the force needed to exit the system.

1. An excessively noisy engine. If the exhaust manifold is leaking, you will hear intermittent popping or hissing noises while the engine is running.

2. Reduced fuel efficiency. An oxygen sensor thrown off by a leaking manifold can affect fuel delivery. The result is increased fuel consumption and emissions.

3. Exhaust odor. You will notice an exhaust odor coming from the engine compartment.

4. Illuminated check engine light. The leak may cause the car's sensors to trigger the check engine light.

5. Poor vehicle performance and acceleration. Similar to how an exhaust manifold leak can lead to lower fuel efficiency, it can make it harder for your car to accelerate.

6. Reduced engine performance. The air-fuel mixture can become unbalanced, resulting in poor engine performance.

7. Inaccurate oxygen sensor readings. You can check the oxygen sensors, which provide important information about the air-fuel ratio in your engine.

8. Visible rust on the manifold. Since the manifold is made of metal, it is susceptible to rust.  When rust is severe enough to cause holes or cracks in the manifold.

9. Visible damage, such as cracking. The most obvious sign of a cracked manifold is, well, a crack on the surface of the manifold.

1. Open the hood and locate the exhaust manifold.

2. Remove the heat shield covering the manifold.

3. Identify where the part is damaged. the small tubes, a gasket, or other accessory.

4. Sand the damaged area with low grit sandpaper to remove rust and dirt.

5. Thoroughly clean the part with a foaming engine cleaner.


Method 1

Step 1: Prepare a container of thermal metal repair paste.  Be sure to select a paste that's rated for at least 650°C.

Step 2: Thoroughly mix the paste until it's a uniform thickness.

Step 3: Apply a liberal amount of paste evenly to the crack.

Step 4: Allow the paste to cure for at least 24 hours before starting your vehicle.


Method 2

Step 1: Prepare a welding torch.

Step 2: Set the oxyacetylene torch to its lowest heat setting.

Step 3: Place the tip of the silver solder against the crack in the damaged exhaust manifold.

Step 4: Use a size one solder tip and hold the torch very close to melt it onto and into the crack.

Step 5: Use gentle strokes over the area.

Step 6: Continue to work the solder into the crack of the exhaust manifold until you have completely filled it.

Step 7: Fill any remaining small holes with a compound such as JB Weld.

Step 8: Allow the iron to cool naturally.

1. Headers create less exhaust back pressure than manifolds.

2. Manifolds are typically made of thick cast iron; headers are typically made of thin-walled stainless steel tubing.

3. Each header has long, equal-length primary tubes; manifolds have short, variable-length inlets.

4. Headers are less likely to rust or corrode than cast iron manifolds.

5. Manifolds are found on most stock production vehicles, while headers are found on modified or performance vehicles.

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