Crankcase
The lower section of the engine block that houses the crankshaft and contains the engine oil.
The crankcase is the lower section of the engine block that encloses the crankshaft and connecting rods. Its primary role is to protect these rapidly rotating internal components and house the engine oil supply, with the oil pan bolted to the bottom of the crankcase.
During engine operation, the combustion process creates pressure in the cylinders. A small amount of exhaust gas and unburned fuel blows past the piston rings and enters the crankcase, a phenomenon known as **blow-by**. If these gases are not vented, they build up pressure, which can blow out engine gaskets and oil seals, causing leaks.
To manage this pressure and prevent oil contamination, vehicles use a **Positive Crankcase Ventilation (PCV)** system. The PCV valve uses intake manifold vacuum to safely draw blow-by gases out of the crankcase and route them back into the combustion chambers to be burned.
Keeping the crankcase free of excessive pressure and oil sludge is critical for engine longevity. Regular oil changes prevent sludge buildup, and maintaining a functional PCV system protects gaskets from blowing due to crankcase over-pressurization.