How to replace the exhaust manifold gasket

Exhaust manifold gaskets seal gaps to keep exhaust gases out of the exhaust system, as well as reduce engine noise and improve fuel efficiency.

Used as a source of sealing for any gap between the cylinder head outlet port and the exhaust manifold, the exhaust manifold gasket is one of the most important gaskets in a vehicle. Not only does this component prevent toxic exhaust gases from escaping from the engine before they enter the after-treatment system, but it also helps reduce engine noise, improve fuel efficiency, and can affect the power your engine produces.

Before the exhaust exits the tailpipe, it passes through a series of exhaust pipes and connections to reduce engine noise, remove harmful exhaust gases and increase engine efficiency. This process begins as soon as the exhaust valve opens and the freshly burned fuel is expelled through the cylinder head exhaust port. The exhaust manifold, connected to the cylinder head by a gasket between them, then distributes the gases throughout the exhaust system.

These gaskets are usually made from embossed steel (in multiple layers depending on the thickness required by the engine manufacturer), high temperature graphite, or, in some cases, ceramic composites. The exhaust manifold gasket absorbs intense heat and toxic exhaust fumes. In most cases, exhaust manifold gasket damage is caused by excessive heat coming from one of the exhaust ports. When carbon builds up on the walls of the cylinder head, it can sometimes ignite, causing the exhaust manifold gasket to "fire" or burn out in one particular spot. If this happens, the seal between the exhaust manifold and the cylinder head may leak.

When an exhaust manifold gasket has been "squeezed out" or "burnt out", it must be replaced by an experienced mechanic. On older vehicles, this process is quite simple; due to the fact that the exhaust manifold is often open and easily accessible. Newer vehicles with advanced sensors and additional emission control devices can often make it difficult for a mechanic to remove exhaust manifold gaskets. However, just like any other mechanical component, a bad or faulty exhaust manifold gasket can have several warning signs, such as:

• Insufficient engine performance: A leaky exhaust manifold gasket reduces the compression ratio during the engine's exhaust stroke. This often reduces engine performance and can cause the engine to choke under acceleration.

• Decreased Fuel Efficiency: A leaky exhaust manifold gasket can also contribute to reduced fuel efficiency.

• Increased Exhaust Smell Under the Hood: If the exhaust manifold seal is broken or squeezed out, gases will escape through it, which in many cases can be poisonous. This exhaust will smell different than the exhaust coming out of the tailpipe.

• Excessive Engine Noise: A leak through the exhaust manifold gasket will often result in unmuffled exhaust fumes that will be louder than normal. You may also hear a slight "hiss" when the gasket is damaged.

Part 1 of 4: Understand the Signs of a Broken Exhaust Manifold Gasket

It is very difficult for even the most experienced mechanic to correctly diagnose an exhaust manifold gasket problem. In many cases, the symptoms of a damaged exhaust manifold and the gaskets underneath are very similar. In both cases, damage will result in an exhaust leak, which is often detected by sensors connected to the vehicle's ECM. This event will instantly activate the Check Engine light and generate an OBD-II error code that is stored in the ECM and can be downloaded using a digital scanner.

The generic OBD-II code (P0405) means that there is an EGR error with the sensor that monitors this system. This error code often tells the mechanic that there is a problem with the EGR system; in many cases it is due to a cracked exhaust manifold due to a faulty exhaust manifold gasket. The exhaust manifold gasket will be replaced if you still need to replace the exhaust manifold gasket. If the problem is with the gasket, you will have to remove the exhaust manifold to inspect and replace.

Part 2 of 4: Preparing to Replace the Exhaust Manifold Gasket

Exhaust manifold temperatures can reach 900 degrees Fahrenheit, which can damage the exhaust manifold gasket. In most cases, this engine part can last the lifetime of your vehicle. However, due to its location and intense heat absorption, damage may occur that will require its replacement.

• Attention: To replace the exhaust manifold gasket, you must first remove the exhaust manifold. Depending on the make, model, and year of your vehicle, other major mechanical systems may need to be removed to gain access to this part. This is work that should only be done using the proper tools, materials and resources to get the job done right.

• Attention: The steps below are general instructions for replacing the exhaust manifold gasket. Specific steps and procedures can be found in the vehicle service manual and should be reviewed before doing this job.

However, in many cases, a blown exhaust manifold gasket can lead to damage to the exhaust head ports. If this happens, you will have to remove the cylinder heads and repair the burnt port damage; as simply replacing the gasket will not solve your problems. In fact, in many situations this can cause serious damage to the exhaust cylinder hardware such as valves, retainers and holders.

If you choose to do this job, you will most likely have to remove a few components to gain access to the exhaust manifold. The specific parts that need to be removed depend on your vehicle, however in most cases these parts will need to be removed in order to have full access to the exhaust manifold:

• engine covers
• Coolant lines
• Air intake hoses
• Air or fuel filter
• Exhaust pipes
• Generators, water pumps or air conditioning systems

Purchasing and studying a service manual will give you detailed instructions for most minor or major repairs. We recommend that you read the service manual before attempting this job. However, if you have gone through all the necessary steps and are not 100% sure about replacing the exhaust manifold gasket on your vehicle, contact your local ASE certified mechanic from AvtoTachki.

Necessary materials

• Boxed wrench(s) or set(s) of ratchet wrenches
• Carb Cleaner Can
• Clean shop rag
• Coolant bottle (additional coolant for radiator fill)
• Flashlight or drop of light
• Impact wrench and impact sockets
• Fine sandpaper, steel wool and gasket scraper (in some cases)
• Penetrating Oil (WD-40 or PB Blaster)
• Replacing the exhaust manifold gasket and exhaust pipe gasket
• Protective equipment (safety goggles and gloves)

• Wrench

• Functions: Some exhaust manifolds on small cars and SUVs are directly connected to the catalytic converter. Like it or not, the exhaust manifold will require two new gaskets.

The first is the exhaust manifold gasket that attaches to the cylinder head. Another gasket that separates the exhaust manifold from the exhaust pipes. Refer to your vehicle service manual for the exact materials and steps for replacing the exhaust manifold. Also, be sure to do this job when the engine is cold.

Part 3 of 4: Replacing the exhaust manifold gasket

• Attention: The following procedure details the general instructions for replacing the exhaust manifold gasket. Always refer to your vehicle's service manual for the exact steps and procedures for replacing the exhaust manifold gasket for your specific make, model, and year of your vehicle.

Step 1: Disconnect the car battery. Disconnect the positive and negative cables to cut off power to all electronic components before removing any parts.

Step 2: Remove the engine cover. Loosen the bolts that secure the engine cover using a ratchet, socket and extension, and remove the engine cover. Sometimes there are also snap-in connectors or electrical harnesses that must be removed in order to remove the cover from the engine.

Step 3: Remove engine components in the way of the exhaust manifold.. Each car will have different parts that interfere with the exhaust manifold gasket. Refer to your vehicle's service manual for instructions on how to remove these components.

Step 4: Remove the heat shield. To remove the heat shield, in most cases, you will need to unscrew two to four bolts that are located on the top or side of the exhaust manifold. See your vehicle's service manual for exact instructions.

Step 5: Spray the exhaust manifold bolts or nuts with penetrating fluid.. To avoid stripping nuts or breaking studs, apply a generous amount of penetrating oil to each nut or bolt that secures the exhaust manifold to the cylinder heads. Wait five minutes before attempting to remove these nuts to allow the liquid to soak into the stud.

After completing this step, crawl under the car or, if the car is on a stand, spray the bolts that connect the exhaust manifold to the exhaust pipes. Most of the time there will be three bolts connecting the exhaust manifold to the exhaust pipes. Spray the penetrating liquid on both sides of the bolts and nuts and let it soak in while you remove the top.

Step 6: Remove the exhaust manifold from the cylinder head.. Remove the bolts that secure the exhaust manifold to the cylinder head. Using a socket, extension, and ratchet, loosen the bolts in any order, however, when installing a new manifold after replacing the exhaust manifold gasket, you will need to tighten them in a particular order.

Step 7: Remove the exhaust manifold from the exhaust pipe.. Use a socket wrench to hold the bolt and a socket to remove the nut (or vice versa, depending on your ability to access this part) and remove the bolts that hold the two exhaust systems. Remove the exhaust manifold from the vehicle after completing this step.

Step 8: Remove the old exhaust manifold gasket. Once the exhaust manifold is removed from the vehicle, the exhaust manifold gasket should slide off easily. However, in some cases, the gasket is welded to the cylinder head due to overheating. In this case, you will need a small scraper to remove the gasket from the cylinder head.

• A warning: If you notice that the cylinder head gasket is stuck to the exhaust ports, you should remove the cylinder heads, inspect them and rebuild if necessary. In many cases, this type of damage is caused by a defective exhaust valve. If not corrected, you will have to perform this step again sooner rather than later.

Step 9: Clean the exhaust ports on the cylinder head.. Using a can of carburetor cleaner, spray it onto a clean shop rag and then wipe the inside of the exhaust ports until the hole is clean. You should also use steel wool or very light sandpaper and lightly sand the outside holes to remove any pitting or residue on the outside of the outlet. Again, if the cylinder head looks discolored or damaged, remove the cylinder heads and have a professional mechanic shop check or repair.

After installing a new gasket, you will need to install the bolts holding the exhaust manifold to the cylinder heads in a certain pattern. Please refer to your vehicle service manual for exact instructions and recommended torque pressure settings for reinstalling a new exhaust manifold.

Step 10: Install a new exhaust manifold gasket.. The steps to install a new exhaust manifold gasket are the reverse of the steps to remove, as listed below:

• Install a new exhaust manifold gasket onto the studs on the cylinder head.
• Apply anti-seize to the cylinder head studs that secure the exhaust manifold to the cylinder head.
• Install a new gasket between the bottom of the exhaust manifold and the exhaust pipes.
• Attach the exhaust manifold to the exhaust pipes under the vehicle after applying anti-seize to each bolt.
• Slide the exhaust manifold onto the cylinder head studs.
• Hand tighten each nut on the cylinder head studs in the exact order specified by the vehicle manufacturer until each nut is hand tight and the exhaust manifold is flush with the cylinder head.
• Tighten the exhaust manifold nuts to the correct torque and exactly as recommended by the vehicle manufacturer.
• Install the heat shield to the exhaust manifold.
• Install the engine covers, coolant lines, air filters, and other parts that have been removed to gain access to the exhaust manifold.
• Fill the radiator with the recommended coolant (if you had to remove the coolant lines)
• Remove any tools, parts, or materials that you have used in this job.

• Connect battery terminals

  • AttentionA: If your vehicle had an error code or indicator on the dashboard, you need to follow the manufacturer's recommended steps to clear old error codes before checking for an exhaust manifold gasket replacement.

Part 4 of 4: Check the repair

When testing the vehicle on fire, any symptoms that were evident before the exhaust manifold gasket was replaced should disappear. After you have cleared the error codes from your computer, start the car with the hood up to perform the following checks:

• OBSERVE for any sounds that were symptoms of a blown exhaust manifold gasket.
• SEE: for leaks or escaping gases from the exhaust manifold-to-cylinder head connection or from the exhaust pipes below
• OBSERVE: Any warning lights or error codes that appear on the digital scanner after starting the engine.
• CHECK: fluids that you may need to drain or remove, including coolant. Be sure to follow the manufacturer's recommendations for adding coolant.

As an additional test, it is recommended to road test the vehicle with the radio turned off to listen for any road noise or excessive noise coming from the engine compartment.

As stated above, if you have read these instructions and are still not 100% sure about completing this repair, or if you determined during a pre-installation check that removing additional engine components is beyond your comfort level, please contact one of our local certified ASE mechanics from AvtoTachki.com will replace the exhaust manifold gasket.