We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is a Crankcase?

By Mike Howells
Updated May 23, 2024
Our promise to you
WikiMotors is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WikiMotors, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

An intrinsic component of an internal combustion engine, the crankcase is a drilled metal frame that houses several parts, notably the crankshaft. Its main universal function is to shield the crankshaft and the connecting rods from debris. In simple two-stroke engines, the crankcase serves several roles, and is used as the pressurization chamber for the fuel-air mixture. In more complex four-stroke designs, it is sealed off from this mixture by the pistons, and instead works mainly to store and circulate oil. In a four-stroke engine, it sits below the cylinder block, and in both types comprises the largest physical cavity of the motor.

Most modern crankcases are made out of aluminum, which provides a lightweight yet strong design capable of withstanding the pressures exerted during normal engine use. In normally aspirated four-stroke engines, that is engines that do not feature a turbocharger, a small level of pressure in the case is desirable to keep out dust and other potentially damaging particulates, while keeping the oil properly situated. All engines, as part of their normal operation, allow a small amount of unburned fuel and exhaust gas to escape into the crankcase. This collective material is known as blow-by.

A positive crankcase ventilation valve, or PCV valve, is typically employed as part an overall pressure control system, to regulate the amount of blow-by ejected from the crankcase. Passing through the PCV valve, the expelled blow-by is returned through the system, back to a part known as the intake manifold, where it is re-used in the combustion process. This design was adopted in part by legislative impetus, because earlier designs were not enclosed and allowed blow-by to escape directly out of the engine, generating significant environmental damage. PCV systems are not used in two-stroke engines, as all blow-by is burned in the normal flow of air and fuel.

Proper care of the crankcase and its internal components is essential to the smooth running of an engine. Maintaining a proper amount of clean oil is crucial, and is measurable by using a simple tool known as a dipstick, a simple length of metal that visibly shows the level of oil. While checking it regularly will show how much oil is present, unburned fuel that collects in the crankcase can negatively impact the lubricating quality of the oil, so regular oil changes are vital. Additionally, an improperly broken-in engine or one with dry, cracked piston seals can allow too much gas to leak past the pistons into the crankcase, generating dangerously high levels of pressure that can cause engine damage and failure. Early symptoms of failing seals include oil leaking out of the PCV valve or past the dipstick.

WikiMotors is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By Theborgrote — On Jan 31, 2014

It's very important to keep an eye on your oil level and mileage in between oil changes. While many mechanics and oil manufacturers will tell you to change your oil every 3,000 miles, I've found that doing so about every 5,000 miles or so is sufficient. In fact, a mechanic at a Chevrolet dealer from whom I once bought a truck told me that changing your oil every 5,000 miles is perfectly fine and will not harm your engine.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.

WikiMotors, in your inbox

Our latest articles, guides, and more, delivered daily.