An exhaust leak can affect how your car runs or it can mostly just make your car’s exhaust louder. The increase in sound output from your exhaust system can actually lead to a ticket for excessively loud exhaust in some areas. If the leak is occurring in the manifold gasket or the manifold flange gasket area, excessive heat can build up which can quickly burn an exhaust valve, which will be an expensive repair bill. A leak farther downstream before the catalytic converter can trick the oxygen sensor into thinking the engine is running leaner than it really is, which will cause the computer to dump more gas into the cylinders. This is how an exhaust leak can hurt your car.