The exhaust manifold gasket is responsible for the tightness of the joint between the exhaust manifold and the cylinder head. This ensures a normal operation of the vehicle, and, as a result, improves its safety.
Considering how important safety is when driving a car, it is no wonder why the condition of the exhaust manifold gasket is that crucial. In this article, you will have the chance to learn more about the exhaust manifold gasket and how you can change it in case you ever need to do that. Let's get rolling!
Which are the functions of the exhaust manifold gasket?
The exhaust manifold gasket, which is part of the vehicle's exhaust system, serves to remove exhaust gases from the cylinders into the exhaust pipe. Additionally, the exhaust manifold gasket is designed to improve the process of filling the combustion chambers.
Another thing to keep in mind is that the manifold gasket works at high pressures and temperatures. Its main task is to prevent exhaust gases from entering the engine compartment. It may well cause the ignition of units and parts of the engine compartment.
The exhaust manifold is made of stainless steel or high heat-resistant cast iron. Usually, the manifold has excellent durability. In fact, it is super rare to ever need to fix the manifold in a modern car. Experts say that the manifold gasket can fail only when cracks form on its surface caused by moisture on the hot metal.
However, they have to be periodically changed both on cars with high mileage and also in new cars. In the second situation, premature wear of the gaskets can be caused by the following reasons:
- Low quality of the sealant;
- Intensive vehicle operation in difficult road conditions;
It has different mountings and configurations in different cars. Nevertheless, the main thing you should remember is that the task of the exhaust manifold is to transfer combustion products collected from all cylinders to the intake pipe. The gases from the VC go to the catalyst or directly to the exhaust pipe and then to the muffler.
Causes of exhaust manifold gasket's failure
The manifold gasket is placed between the exhaust manifold and the cylinder head. The stamped manifold gasket is resistant to high temperatures. It can shrink (creating the necessary impermeability) and has increased strength.
To enhance the latter quality, the exhaust manifold gaskets are additionally reinforced with steel. Another thing to keep in mind is one of the key roles of the gasket is to prevent a concentration of exhaust gases under the hood where they can provoke ignition of parts/assemblies of the engine compartment.
The gasket is recognized as the most vulnerable point of the exhaust manifold since it is operating under high temperature and pressure. It is not surprising that the gaskets have to be changed not only on cars with high mileage but also on practically new cars. The manifold gaskets need to be replaced for several reasons:
- Poor factory quality;
- Overheating of the engine due to intensive use;
- Engine repair (a used gasket loses its properties when dismantled).
Signs of a burnt manifold gasket
Usually, it is the ECU (electronic control unit that signals a gasket malfunction to the dashboard, where the check light comes on. This means that the lambda probe, which is usually equipped with the manifold, recorded a change in the amount of oxygen in the exhaust, informing the ECU. This is when the engine starts to work in emergency mode until the defect is eliminated. Additional signs of a burnt gasket:
- The engine is unstable;
- Makes an uncharacteristic sound during operation;
- The cabin smells like exhaust gases.
Exhaust gasses through the ventilation and heating systems quickly gets to the passenger compartment. This usually results not only in a deterioration of the microclimate but also with negative health consequences. That is why replacing the exhaust manifold gasket is a must. By the way, if throughout this process you find out that you should also fix the throttle body, check out our other blog post that covers that topic.
When to replace the manifold gasket?
The durability of the exhaust manifold gasket does not depend on the period of its use and the mileage of the car. It is capable of performing its assigned functions for 2, 5, or 10 years. The duration of its service is determined by the condition of the engine and the quality of the fuel. Keep in mind that the better the fuel is, the less often you will have to resort to replacing the gasket.
Nowadays, gaskets are made of pressed high-strength asbestos, which, is also reinforced with steel. However, even such a reliable material does not withstand the loads with which it has to face over time. And at one moment, the driver realizes that the gasket on the manifold of his vehicle has burned out. This means that it needs to be immediately replaced with a new one. How does a driver identify a broken gasket?
It is very simple. Some signs of manifold gasket's failure include: the smell of exhaust gases is noticeably heard in the cabin; the car engine does not start well; from under the hood of the car, an unpleasant characteristic sound is heard, etc. As soon as the driver faces the above symptoms, he/she should immediately start checking the exhaust system for leaks. It is not difficult to identify a leak in the place where gases breakthrough, you can learn more about it here.
And if the gasket is to blame, it must be changed immediately. See below for how to do this!
How to change an exhaust manifold gasket?
The main sign of an exhaust gasket is considered to be the soot that forms in the place where the exhaust bursts. In this case, you should proceed to replace the unusable seal. To replace the exhaust manifold gasket, it is necessary to get the following materials and tools:
- sharp knife (remove the used gasket);
- spanner keys;
- anti-rust liquid
- a container with a wide neck for 5 liters (for draining antifreeze);
- dry rags.
Remember that when replacing the manifold gasket, it is necessary to drain the antifreeze in advance, otherwise, you can fill the engine inlet windows.
Removing the air filter
First, it is advisable to clean the filter cover from dirt. Then you loosen the hose clamp and disconnect the ventilation pipe. Three holders are removed from the cover, and the screw in the center is unscrewed. The cover can then be removed.
After that, you can remove the filter element itself. Cover the hole in the carburetor with a cloth or rag so that no parts get caught. The filter housing is released by loosening four nuts. Then remove the mounting plate holding the filter housing. It will be useful to thoroughly clean it from dust and dirt. On injection engines, the air filter cover is removed by unscrewing the screws.
Therefore, for this, you will definitely need a Phillips screwdriver to loosen the MFRV sensor clamp. After that, the sensor itself will be disconnected by disconnecting the wiring block and removing the rubber sleeve for the air supply. Then the filter element itself is removed.
Next, the air intake tip of the filter housing is removed from the holder. To remove the filter housing, loosen the four nuts. Finally, disconnect the hoses and remove the filter housing.
Removing the carburetor
Here you start by removing the cable from the air damper. Use the key to loosen the tightening of the shell fastening. Then unscrew the cable securing screw with a screwdriver and remove it. Next, remove the gas outlet hose from the crankcase. Then you disconnect the two wires from the EPHH. After you are done with that, pry the rod off the throttle lever and remove it.
After that, you should disconnect the hoses of the ignition timing regulator and the EPHH control valve. Remove the return spring with your hands. Take off the fuel hose after loosening the clamp. Finally, unscrew the nuts securing the carburetor to the intake manifold and remove the carburetor to a safe place. It is advisable to close the opening of the inlet pipeline with a plug.
Replacing the manifold gasket
Before disassembling the exhaust gasket, it is recommended to drain the coolant. The reason is simple, if you don't do this it can enter the engine and cause unpleasant and painstaking flushing. To do this, first, you need to bend the lock washers of the nuts with a screwdriver. After that, the burnt pants are freed from the pins and taken to the side.
It is important to follow this process carefully and not to damage the studs. Before disconnecting the manifold, move the coolant hose to the side. Unscrew the remaining three nuts from the manifold and pull it back, freeing it from the retaining pins. Typically, the manifold gasket adheres firmly to the cylinder head so just gently pry it off with a sharp knife. Finally, clean the flanges of the collector and exhaust pipe with zero sandpaper.
It is advisable to clean the surface where the gasket was located with a special spray for deeper cleaning. After applying the spray, wait 15 minutes and clean the carbon deposits with a rag. You can apply graphite grease to the manifold mounting studs. To learn more about exhaust gaskets, check out our other article that covers that topic in more detail.
The process of replacing the seal when it fails is simple but is different for different engines. In general terms, the algorithm for dismantling and subsequent installation of the manifold gasket should be like this:
- Open the hood and remove the air intake with the carburetor, under which the manifold is located.
- Remove the thermal shield.
- Unscrew the bolts that secure the "spider" to the exhaust pipe, and then the bolts that connect to the engine block.
- Start removing the exhaust manifold itself, on which the burned-out gasket sits, often "sticking" to the VC.
- Thoroughly clean the joint between the cylinder head and the manifold with a spatula, removing carbon deposits and fragments of the worn gasket from the second.
- After the area is shiny, coat it with graphite grease and install a new gasket.
- Apply the same grease (to prevent corrosion) on the fasteners.
Finally, return all dismantled parts back to their place.
A step-by-step guide to replace the manifold gasket
To replace the manifold gasket, you should first, remove the engine protection from the car standing on the overpass, drain the antifreeze and jump to the following steps:
- Remove the air filter after having thrown off the negative terminal of the battery.
- Try disconnecting the fuel pipes with the accelerator cable from the throttle.
- Disconnect the idle / throttle sensors.
- And also disconnect the crankcase ventilation and brake booster hoses, turning off the receiver.
- Remove the latter by disconnecting the wires at the injection control unit.
- Dismantle the fuel rail without unscrewing the injectors.
- Detach the front pipe from the VC.
- Remove the intake and exhaust manifolds.
- Remove the old gasket.
- Clean the joint between the manifold and the cylinder head with a knife.
- Put a new gasket, making a reverse installation.
- Fill in the coolant.
Remember that an exhaust manifold gasket will last a long time if you use quality fuel and control the level of antifreeze to prevent engine overheating. Another thing you can do to prevent complete failure of the manifold gasket is to check the reliability of the joint between the cylinder head and the VC and immediately change the gasket after you notice its malfunction.
Replacing the exhaust manifold gasket on any engine is quite difficult and not that simple as many believe. This can be a real challenge for many new drivers. Nevertheless, if you follow the instructions, then everything should work out just well. In case you are still hesitant about whether you should accept this challenge or not, then maybe you should visit some car service.
Moreover, if you decide to replace it by yourself, pay attention to the quality of the products you use while doing the work. That will ensure the manifold gasket to serve your needs for a long time to come.