Exhaust manifolds are usually made from porous metals that expand and contract depending on the temperature. This makes them more prone to cracks over time. Once your car's exhaust manifold breaks, the engine's performance will be affected because of the unequal air-to- fuel ratio. The exhaust manifold is the key component in the exhaust system on a vehicle. It is responsible for collecting the exhaust gas from the engine's cylinder heads and sending it down to the exhaust pipe. At the same time, it prevents any toxic exhaust fumes from leaking into the passenger area of the vehicle.