The exhaust manifold connects the cylinders in an engine to the exhaust tailpipe, and as a result, processes a great deal of heat, smoke, and oil. The result is that it requires frequent cleaning, repairing, and changing. If your exhaust manifold is broken or has gone out, then you can easily change it with a new one by following a few simple steps.
Check the Owner's Manual for Your Vehicle
The first step to changing an exhaust manifold is to refer to the part guide or the owner's manual for your vehicle. Most manufacturers put the exhaust manifold in a slightly different place, so you may have to access the underside of the vehicle, or remove the fan or other parts from under the bonnet to get to it. In either case, you can always locate the exhaust manifold on one side of the cylinder; the intake manifold is on the other side, or may be bolted to the exhaust manifold. The owner's manual should also tell you which new manifold and tools you need.
Remove the Old Exhaust Manifold
Once you have located the old exhaust manifold, remove it using a power wrench or manual wrenches and sockets. Keep in mind that there should be at least four to eight bolts connecting the manifold to the engine block and cylinder, and possibly several more connecting the intake manifold to the exhaust manifold. You have to remove all of the bolts, which may require several different size wrenches or sockets, so keep a socket set nearby. Lubricating the bolts before removal ensures that they come out more smoothly, especially if they were put in using air tools. V8 engines have more than one exhaust bank, so you have to remove one exhaust for each cylinder bank.
Replace the Exhaust Manifold
Most of the time, you only have to change an exhaust manifold gasket or part of the exhaust manifold, but you may want to replace the whole thing, or upgrade it to a performance exhaust manifold. In either case, you have to replace everything exactly how it was in the engine. If you are using a turbo exhaust manifold, follow the instructions that came with the manifold. If using a factory OEM model, such as for a Honda Civic, then simply insert it into the space left by the old one, bolt it to the frame, and then lubricate the parts. If you are installing a performance exhaust manifold, then you may have to have it professionally or custom fitted if it does not exactly match the current manifold in your engine.