What is a Crankcase?
2 Answers
The crankcase is the part located below the cylinder block where the crankshaft is installed. The crankcase is divided into the upper crankcase and the lower crankcase. The oil pan, which bears relatively little force, is typically made of stamped thin steel sheets, and its shape depends on the overall layout of the engine and the capacity of the engine oil. Additional information: 1. Composition: The upper crankcase is cast integrally with the cylinder block, while the lower crankcase is used to store lubricating oil and seal the upper crankcase, hence it is also referred to as the oil pan. The oil pan, subjected to minimal force, is generally made of stamped thin steel sheets, with its shape determined by the engine's overall layout and the oil capacity. 2. Function: The oil pan is equipped with stabilizing baffles to prevent excessive oil surface fluctuations when the vehicle is jolted. Additionally, a drain plug is installed at the bottom of the oil pan, often embedded with a permanent magnet to attract metal particles from the lubricating oil, thereby reducing engine wear. A gasket is placed between the upper and lower crankcase mating surfaces to prevent lubricating oil leakage.
The crankshaft case is located at the very bottom of the engine, serving as a large metal housing for the crankshaft and connecting rod components. When I usually repair cars and disassemble the engine, I can see it—it looks like a metal bathtub filled with engine oil submerging the crankshaft. When the pistons push the connecting rods to drive the crankshaft's high-speed rotation, it relies entirely on the oil inside the crankshaft case for lubrication and protection. The bottom of the case is equipped with a drain plug, which must be unscrewed during every maintenance session to change the oil. Sealing is particularly crucial; if the gasket ages and causes oil leaks, the engine can quickly be ruined. Some vehicles have cooling fins designed on the outer walls of the crankshaft case to help dissipate engine heat. If cracks are found in the crankshaft case during repairs, it must be replaced immediately—otherwise, a few thousand dollars in repair costs could escalate into a ten-thousand-dollar overhaul.
