How to replace the exhaust manifold

Exhaust manifolds remove exhaust gases during the exhaust stroke. Engine running problems and engine noise are signs of an exhaust manifold replacement.

Since the inception of the internal combustion engine, the exhaust manifold has been used to efficiently vent burnt exhaust gases outside the engine during the exhaust stroke. Location, shape, dimensions, and installation procedures vary by vehicle manufacturer, engine design, and model year.

One of the most durable mechanical parts of any car, truck or SUV is the exhaust manifold. The exhaust manifold, used in all internal combustion engines, is responsible for the effective collection of exhaust gases coming from the exhaust port on the cylinder head, for the distribution of exhaust gases through the exhaust pipes, through the catalytic converter, muffler and then through the tail section. a tube. They are usually made of cast iron or stamped steel due to the fact that they collect a huge amount of heat while the engine is running.

The exhaust manifold is connected to the cylinder head; and has a custom design to match the exhaust ports on the cylinder head. Exhaust manifolds are an engine component found on all internal combustion engines. Exhaust manifolds made from cast iron are usually a solid piece, while stamped steel consists of several sections welded together. Both of these designs are tuned by vehicle manufacturers to improve the performance of the engines they support.

The exhaust manifold absorbs intense heat and toxic exhaust gases. Due to these facts, they may be susceptible to cracks, holes, or problems with the inside of the exhaust manifold ports. When an exhaust manifold wears out or breaks, it usually displays several warning indicators to alert the driver to the presence of a potential problem. Some of these warning signs may include:

Excessive engine noise: If the exhaust manifold is cracked or leaking, exhaust gases will leak out but will also produce unmuffled exhaust that is louder than normal. In some cases, the engine will sound like it's a racing car, which is the kind of loud noise a cracked exhaust pipe or manifold can make.

Decreased engine performance: Although the noise may sound like a racing car, the performance of an engine with a leaky exhaust manifold will not. In fact, in most cases, an exhaust leak can reduce engine efficiency by as much as 40%. This causes the engine to “choke” under acceleration.

Strange "smell" from under the hood: When the exhaust gases are distributed throughout the exhaust system, they are circulated through the catalytic converter, which removes a large percentage of particulate matter or unburned carbon from the exhaust gases. When there is a crack in the exhaust manifold, gases will leak out of it, which in many cases can be toxic. This exhaust will smell different than the exhaust coming out of the tailpipe.

When you combine all three of these warning signs, it becomes pretty obvious that there is an exhaust leak somewhere near the engine. It is the mechanic's job to determine the exact location of the exhaust leak in order to correctly diagnose the damaged component and make the appropriate repairs. Exhaust manifolds can reach temperatures in excess of nine hundred degrees Fahrenheit. This is why most exhaust manifolds are protected by a heat shield to protect other engine components such as wires, sensors, and fuel or coolant lines.

• Attention: Removing the exhaust manifold on any car is a very long and tedious process; as with most things, you will need to remove a few engine components to access and remove the exhaust manifold. This work should only be done by an experienced mechanic with the proper tools, materials and resources to do the job properly. The steps below are general instructions for replacing an exhaust manifold. Any mechanic is advised to purchase and review their vehicle's service manual for the exact steps, tools, and methods for replacing this part; as it will vary considerably for each vehicle.

Many mechanics prefer to remove the engine from the vehicle in order to replace the exhaust manifold, however this is not always necessary.

Part 1 of 5: Determining the Symptoms of a Broken Exhaust Manifold

A broken exhaust manifold will negatively affect the operation of any internal combustion engine. In many cases, an exhaust leak can be detected by sensors connected to the vehicle's ECM. When this happens, the Check Engine light will usually come on on the dashboard. This will also trigger an OBD-II error code that is stored in the ECM and can be downloaded using a digital scanner. In some cases, an OBD-II code (P0405) will indicate an EGR error with the sensor that monitors this system. While this can be caused by a problem with the EGR system, in many cases it is due to a cracked exhaust manifold or a failed exhaust manifold gasket.

Although the exhaust manifold is not assigned an exact OBD-II error code, most mechanics will use physical warning signs as a good starting point for diagnosing a problem with this part. Because the job of replacing an exhaust manifold can be tricky (depending on the accessory parts that need to be removed on your particular vehicle, it's important to make sure the part is broken before trying to replace it. If in doubt, contact your local ASE certified mechanic who can help diagnose this problem and replace the exhaust manifold for you if necessary.

Part 2 of 5: Preparing the Vehicle for Exhaust Manifold Replacement

Once the engine covers, hoses and accessories are removed, accessing the exhaust manifold and replacing it is a fairly simple process. This diagram shows that you need to remove the heat shield, then the exhaust pipes, exhaust manifold and the old exhaust manifold gasket (which is made of metal).

Once you or a certified mechanic have diagnosed that the exhaust manifold is broken and needs to be replaced, there are two ways to do it. First, you may decide to remove the engine from the vehicle to effectively complete this process, or you may attempt to replace the exhaust manifold while the engine is still inside the vehicle. In many cases, the biggest hurdle or waste of time is the removal of ancillary parts that prevent you from accessing the exhaust manifold. Some of the more common parts that need to be removed include:

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

We are not in a position to articulate exactly which items need to be removed, as each vehicle manufacturer is unique. This is why we highly recommend that you purchase a service manual for your exact make, year and model of the vehicle you are working on. This service manual contains detailed instructions for most minor and major repairs. However, if you've gone through all the necessary steps and don't feel 100% sure about replacing the exhaust manifold on your vehicle, contact your local ASE certified mechanic from AvtoTachki.

Necessary materials

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

• Wrench

• FunctionsA: According to most service manuals, this job will take three to five hours. This work will be accessible through the top of the engine bay, however you may have to lift the car to remove the exhaust manifold with the exhaust pipes underneath the car. Some exhaust manifolds on small cars and SUVs are directly connected to the catalytic converter. In these cases, you will be replacing the exhaust manifold and catalytic converter at the same time. Refer to your vehicle service manual for the exact materials and steps for replacing the exhaust manifold.

Part 3 of 5: Exhaust Manifold Replacement Steps

The following are general instructions for replacing an exhaust manifold. The exact steps and location of this part are unique to each vehicle manufacturer. Please refer to your vehicle's service manual for the exact steps required to replace this component.

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. Most cars made after 1991 have an engine cover that blocks access to the exhaust manifold. Most engine covers are held in place by a series of snap connections and bolts. Unscrew the bolts with a ratchet, socket and extension and remove the engine cover.

Step 3: Remove engine components in the way of the exhaust manifold.. Every car will have different parts in the way of the exhaust manifold that need to be removed before you attempt to remove the exhaust heat shield. Refer to your vehicle's service manual for instructions on how to remove these components.

The heat shield will vary in size, shape, and materials it is made from, but will typically cover the exhaust manifold on most domestic and imported vehicles sold in the US after 1980.

Step 4: Remove the heat shield. On all cars, trucks, and SUVs built after 1980, U.S. automotive laws required a heat shield to be installed over the exhaust manifold to reduce the chance of a vehicle fire caused by burning fuel lines or other materials that come into contact with the excess heat generated. on the exhaust manifold. 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.

Step 5: Spray the exhaust manifold bolts or nuts with penetrating fluid.. Due to the excessive heat generated by the exhaust manifold, it is possible that the bolts that secure this component to the cylinder head will melt or rust. To avoid breaking the studs, apply a generous amount of penetrating lubricant to each nut or bolt that secures the exhaust manifold to the cylinder heads.

Once this step is complete, you can follow this step under the car where the exhaust manifold connects to the exhaust pipes. There are usually 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.

Remove the exhaust manifold using a socket, extension and ratchet. If you have access to impact or pneumatic tools and have room in the engine bay, you can use these tools to remove the bolts.

Step 6: Remove the exhaust manifold from the cylinder head.. After the bolts have been soaked for about 5 minutes, remove the bolts that secure the exhaust manifold to the cylinder head. Depending on the vehicle you are working on, there will be one or two exhaust manifolds; especially if it's a V-twin engine. Remove the bolts in any order, however, when installing a new manifold, you will need to tighten them in a certain order.

Step 7: Remove the exhaust manifold from the exhaust pipe: Once you've removed the bolts holding the exhaust manifold to the cylinder head, crawl under the car to remove the bolts and nuts holding the exhaust manifold to the exhaust system. In most cases, there is a bolt on one side and a nut of the appropriate size on the other. Use a socket wrench to hold the bolt and a socket to remove the nut (or vice versa, depending on your access to this part).

Step 8: Remove the old exhaust manifold gasket. On most vehicles, the exhaust manifold gasket will be metal and will easily come off the cylinder head studs once you remove the exhaust manifold from the vehicle. Remove the old exhaust manifold gasket and discard.

• A warning: Do not reuse an old exhaust manifold gasket when installing a new exhaust manifold. This can lead to compression problems and damage to internal engine components, increase exhaust leakage and be hazardous to the health of those traveling in the vehicle.

Step 9: Clean the exhaust ports on the cylinder head.. Before installing a new exhaust manifold, it is important to remove excess carbon deposits on the exhaust ports or inside the exhaust port. 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. Also, using steel wool or very light sandpaper, lightly sand the outside surfaces of the holes to remove any pitting or residue on the outside of the outlet.

On most vehicles, you will need to fit the exhaust manifold bolts to the cylinder heads in a specific pattern. Please refer to your vehicle service manual for exact instructions and recommended torque pressure settings for reinstalling a new exhaust manifold.

Part 4 of 5: Install the new exhaust manifold

The steps to install a new exhaust manifold are the reverse of the removal steps, as shown below:

Step 1: Install a new exhaust manifold gasket onto the studs on the cylinder head..

Step 2: Install a new gasket between the bottom of the exhaust manifold and the exhaust pipes..

Step 3: Attach the exhaust manifold to the exhaust pipes under the car..

Step 4: Slide the exhaust manifold onto the cylinder head studs..

Step 5: Hand tighten each nut on the cylinder head studs.. Tighten the nuts in the exact order specified by the vehicle manufacturer until each nut is finger tight and the exhaust manifold is flush with the cylinder head.

Step 6: Tighten the exhaust manifold nuts.. Tighten to the correct torque and exactly as recommended by the vehicle manufacturer.

Step 7: Install the heat shield to the exhaust manifold..

Step 8: Reattach the Parts. Install the engine covers, coolant lines, air filters, and other parts that have been removed to gain access to the exhaust manifold.

Step 9: Fill Radiator with Recommended Coolant. Top up with coolant (if you had to remove the coolant lines).

Step 10 Remove all tools, parts or materials that you used in this work..

Step 11: Connect the battery terminals.

• AttentionA: You will need to start the engine to make sure this job has been completed. However, 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 replacement.
  
  

Part 5 of 5: Repair Check

Since most exhaust manifold problems are easy to identify by sound or smell after you check the car; repair should be obvious. After you have cleared the error codes from your computer, start the car with the hood up to perform the following checks:

LOOK FOR: any sounds that were symptoms of a broken exhaust manifold

LOOK 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.

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 the pre-installation check that removing additional engine components is beyond your comfort level, contact one of our local certified ASE mechanics from AvtoTachki.com will replace your exhaust manifold.