The crankcase is where it is deposited Oil in charge of engine lubrication. Hence, it has a shape similar to that of a bucket or a small bathtub screwed to the bottom of the engine. Just above him is the crankshaft, Rods and above the pistons.
The reason why it is in the lowest part of the engine is because the oil ends up falling there due to gravity. The oil pump it sucks the lubricant out of it to the top of the engine, but it always falls back into the crankcase once it has lubed up all the parts. In this way you create a cycle that keeps the engine lubricated at all times.
crankcase parts
upper casing
The engine crankcase can be broken down into several very important parts. The first of them is called upper crankcase or the crankshaft. must have one high stiffness since all the force and vibrations that are produced by the movement of the engine affect it. For this reason, it must be made of a good material that guarantees the correct functioning of the motor assembly.
lower sump
The second part is called lower crankcase or oil. This piece is fixed to the previous one thanks to some screws and it is the one with the shape of a bucket. Between the oil pan and the crankshaft there is a gasket to ensure the tightness of the assembly and prevent oil from escaping.
gasket and screws
To ensure that there are no oil leaks at the junction of the parts, a sump It will always come with the corresponding gasket and screws.. Although the assembly is apparently simple, all the screws have to be tightened with the torque indicated by the manufacturer, since if we go too far we can deform the crankcase and create gaps through which the oil is lost.
In turn, the crankcase has a screw through which the oil will be dislodged when you are going to change. An equally important part that should be checked frequently for oil leaks.
car sump cover
Although it is not a part of the crankcase itself, it is important for protect it from possible impacts that occur while driving. In a piece of fiber, plastic or metal that prevents the crankcase from being exposed to irregularities in the ground, stones or other elements that can damage it.
Engine crankcase operation
Despite its apparent simplicity, the crankcase is designed with specific shapes to guarantee the supply of oil. Especially inside. Thanks to this, it is achieved that the oil pump can suck the amount of oil needed for the correct lubrication of our car's engine.
The oil pump is usually in the lowest part of the crankcase so that it can suck in the necessary oil at all times. In the event that our engine has little oil, the pump will not be able to suck in the oil, so we can run the risk of the engine seizing up.
Its shape is also designed so that the inertia of the curves cut off the oil supply as little as possible to the bomb You have to understand that the car can be subjected to some pretty strong G-forces. This causes the oil to drift to one side and may be out of reach of the pump's suction. In cars in which this effect is very pronounced, such as sports cars, a system called dry sump is used.
dry sump
A dry sump system eliminates the oil supply problem caused by the inertia of extremely hard cornering, acceleration and braking. Its operation is based on accumulates the oil in a separate tank, instead of in the crankcase. Hence its name dry sump.
Inside this tank, the oil is prevented from moving excessively with the G forces thanks to some baffle plates. The oil pump always suck up all the oil let it fall into the crankcase with more force than you put it into the engine. In this way, the tank always has all the oil available.
Being sucked in so hard, it also sucks air into the crankcase. But this one is eliminated by thanks to a cyclone separator, which is nothing more than a funnel that generates a vortex with the oil outside and the air inside. As it becomes narrower and narrower, it eliminates the air gap inside it. In the following video you can see how the set works clearly:
2-stroke engines do not have a crankcase
Although it is a frequent element, not all engines have a sump. For example, two-stroke engines do not have a crankcase because oil is supplied mixed with fuel and air. Hence, they normally use more oil than a four-stroke engine. Its crankshaft is inside a cylindrical chamber that hardly leaves any space inside. It is a more typical motor in mopeds and in industrial machines.
Faults in the crankcase
Crack or break
Being such a simple element, a breakdown in the crankcase usually refers to some crack or break produced by a blow or oil leak through gasket due to a bad installation. In these cases, the most common is to change it for a new one. However, there are other possible faults related to it, such as increased pressure in the crankcase in both diesel and gasoline engines. A situation in which other elements intervene and which is usually a symptom of a fault in another part of the engine.
crankcase pressure
To understand this last problem, it is necessary to know how an engine works and, above all, that its operation is not perfect. With the temperature reached by the oil vapors are generated If left unchecked, they can excessively increase the pressure inside the crankcase and cause loss of tightness and other problems.
That is one of the reasons why modern engines have a PVC valve or positive crankcase ventilation. This is responsible for eliminating that excess pressure and introduces them back into the car's intake, so that they are burned in the combustion chambers. In this way, the emission of gases that are harmful to the environment and to people is avoided. If this valve does not work properly, the crankcase pressure can increase considerably, causing serious engine problems.
In addition to oil vapors, the pressure inside the crankcase can also increase in other ways. No matter how well their combustion chambers work, they always will lose some pressure between the piston rings and the cylinders. A pressure that passes to the inside of the crankcase. If the clearance of the pistons is excessive, that pressure will trigger, making the PVC valve have to work harder.
Crankcase change price
If for whatever reason you have to replace the crankcase of your engine, you should know that it is a relatively simple operation, but that it is recommended that it be carried out by a professional. As we have mentioned before, the screws must be tightened with the torque recommended by the manufacturer to avoid deformations in the metal that can cause leaks. The price of its replacement is between 150 and 400 euros. Although this range can be exceeded in some premium or sports models. If only the gasket is going to be changed, the price can be much lower, but it is recommended clean the crankcase well to ensure that its placement is as hermetic as possible.
Picture 4 – Graham Robertson