An exhaust manifold is the part of a vehicle that collects gases and exhaust fumes from the engine and directs them to the catalytic converter. A manifold is often made of cast iron and has several different pipes which channel gases from various parts of the engine into one central system. The gases pass through the manifold and are emitted from the vehicle through the exhaust pipe. Due to the extreme heat of the gases, the manifold is subject to cracks or leaks.
Examine the manifold to see if it is cracked or leaking. If it leaking but not cracked, follow the steps for removal and replacement of new gaskets. Also check the manifold mounts to see if they are securely attached to the car. Inspect the entire exhaust system, including the pipes, for other cracks or holes.
Remove the exhaust manifold from the engine. Unbolt the nuts and studs that attach the manifold to the engine. You may need to use swivelling sockets or S and U wrenches to detach them.
Mark where the crack or leak is in the exhaust manifold. Clean the area around the leak in the manifold pipe for the best weld.
Use an oxyacetylene torch to repair the crack. Weld the crack making sure the oxyacetylene torch is used at a high temperature. If needed, hire a professional welder for this step.
Attach the exhaust manifold to the engine again. Make sure all gaskets, nuts, bolts, studs or washers on the exhaust manifold are replaced with new ones. Intense heat from the exhaust gases means parts need to be able to withstand the high temperatures. See that no dust or dirt are present when reattaching as this can cause leaks. Make sure all attaching bolts are tightened correctly.