aluminum turbo charger manifold

As the engine pumps hot exhaust gases out of the cylinder head, the exhaust manifold collects it, building pressure. 

Some exhaust manifolds are designed to store the extreme heat caused by the still-burning exhaust gases leaving the individual cylinders. This helps burn any residual fuel in the exhaust before the gas is sent to the next emission device, the catalytic converter. 

What are the symptoms related to a bad exhaust manifold?

If the exhaust manifold gets corroded to the point of cracking, you'll hear a tapping sound. Other possible symptoms include black smoke from the exhaust when you accelerate and a lit check engine light.

If the muffler and exhaust pipe are hanging down, it can place additional strain on the exhaust manifold and cause its gasket to leak.