Understand the crankcase’s role in your engine and issues that may arise.
What Is the Crankcase?
The crankcase is situated between the engine block and oil pan. To power your vehicle, its presence lets the crankshaft move freely in order to translate the torque generated by the engine.
Design wise, the crankcase includes upper and lower portions. The upper crankcase aligns with the cylinder block and supports the crankshaft, camshaft and other engine components like the carburetor, generator, air cleaner, fuel pump and oil filter. In certain cases, the cylinder block and crankcase may be cast together as a single unit for greater durability.
The lower portion acts as a guard for the crank and valve movements, simultaneously holding onto the engine oil. From here, the oil will travel to the engine bearings and other parts to provide lubrication. Fins are situated outside of the oil pan to help keep its contents cool.
Due to these factors, the crankcase is considerably large and plays multiple roles regarding the engine’s operation:
- As the engine burns fuel, the crankcase will produce gases.
- The crankcase needs to be sturdy enough to withstand multiple forces related to combustion, including from gas pressure and piston movement.
Based on these aspects and the type of engine, crankcase design will vary:
- A two-stroke engine features a crankcase-compression design. The air-fuel mixture will pass through before it reaches the cylinder. This crankcase also doesn’t hold the engine oil.
- A four-stroke engine will feature a sturdier crankcase capable of withstanding a stronger force. This design is equipped with an oil sump at the bottom, plus a more durable flywheel. Here, the crankcase stores most of the engine’s oil and only sees the residue of the air-fuel mixture.
Along with these components, a one-way positive crankcase ventilation (PCV) valve, plus a tube and vacuum component like an intake manifold, helps control gas accumulation in this portion of the engine.
Issues with the Crankcase
Issues with the crankcase often stem from how the PCV valve controls gases and emissions. Ordinarily, the PCV valve routes them from the crankcase to the engine’s combustion chamber, where they will be burned. This process also helps improve compression in the engine chamber.
However, gases can pass from the pistons to the crankcase and contaminate the motor oil. This results in a thicker, corrosive substance that can clog and damage your engine, as well as release gases that pollute the environment.
With time, deposits of oil from the crankcase can also clog the PCV valve, affecting its performance. For the crankcase itself, holes can develop with time. This increases the risk that engine oil will leak out and not deliver the lubrication parts need to function.
Generally, your engine has a damaged crankcase or PCV valve if you notice the following signs:
- Damaged seals and gaskets
- Oil leaks
- A whistling sound
- A thicker substance dripping from the engine
- A knocking noise
- The check engine light comes on
Servicing the Crankcase
The PCV valve is not included in regularly scheduled maintenance, so it’s important to pay attention to the engine’s performance and make an appointment if you notice any of the above signs. If the crankcase develops a hole, the part can be repaired to better contain oil and help the engine maintain its performance.
If you’re concerned about a defective crankcase or PCV valve, contact DaSilva’s Auto Body for an inspection and recommendations for repairs.