How Does A Banjo Bolt Work?

A banjo bolt is a significant part of a banjo fitting. Banjo bolts are hollow bolts with holes that allow fluid to transfer into the other part of the fitting, which is also designed to have holes. So, how does a banjo bolt work, and why is it called a banjo bolt?

Banjo bolts get their name from the shape of the fitting, which has a large circular section coupled to a thin pipe. This construction gives it the form of a musical instrument known as the banjo. They are often used with fluid systems that control the flow/transfer of pressurized fluid through fluid delivery lines and other components.

There is no need for rotation when being fixed to the host fitting with banjo fittings, so the risk of damage is reduced. Let’s look at how they work.

How Does A Banjo Bolt Work

banjo bolt and fitting

Banjo bolts are also known as internally relieved because of their hollow interior. This open interior allows fluid to flow inside and exit through a small hole at the side. The bolt then locks into a system to control fluid performance and pressure.

This is why they are commonly found in automobiles’ fuel, motor oil, power steering, and hydraulic systems, notably the clutch and brake systems. In such systems, the banjo bolt attaches the brake lines to the cylinder to regulate the pressure in response to the activation of the brake pedal.

So what is banjo bolt-on brakes? They are essentially connectors that link brake-fluid lines to brake cylinders. Banjo bolts are built to handle extremely high pressure, which is critical for many fluid systems. The importance of banjo brakes is most apparent with hydraulic systems designed to transform light pressure into more power.

With such systems, the fluid is held under pressure, and it is the pressurized fluid that allows the system to function the way it does. Any loss of pressure weakens hydraulic systems, so hydraulic banjo fittings are a crucial part of hydraulic brake systems.

A well-installed banjo bolt has a very tight seal, further reinforced by a banjo bolt washer that is fitted to it. These washers allow fluid to pass around the bolt, so the holes in the bolts do not need to line up, so the installation of flexible lines becomes easier.

 That said, banjo bolts often come with a rating that provides information about the best pressure limits for the bolts. How tight should a banjo bolt be? The amount of torque applied should be in line with the specific requirements for the particular banjo bolts. Avoid excess torque.

 After some time, banjo bolts need replacement. Although the replacement parts are easily accessible, it is critical to get a bolt with the correct size and configuration.

Banjo bolts can also be easily customized by a trained technician that has the right tools. That is why they are not restricted to brake lines and hoses, though. Vehicle manufacturers also use banjo bolts for oil transfer and on the fuel fittings of gas tanks. Regardless of where they are used, the same principle applies in their operations.

banjo bolt washers


Q: Do You Have To Align Banjo Bolts?

Banjo bolts and fittings do not have to be aligned for them to function correctly. To install them properly, check the inside of the hole which accepts the bolt. You’ll find a ring that goes around the bolt. This design makes it possible for fluid to get into the system regardless of where the hole is on the banjo bolt.

Q: Why Do Brakes Use Banjo Bolts?

Banjo bolts are used in automobile brake systems because they are designed to withstand a lot of pressure. Braking systems require the transfer of pressurized fluids, so to connect brake-fluid lines to brake cylinders effectively, a component that allows this transfer while withstanding pressure is needed.

Once the banjo bolt is tightened, it creates a passage for the brake fluid. The fluid moves through a hole in the side of the bolt.

Q: How Many Washers Does A Banjo Bolt?

The banjo bolt is designed to have two washers—one on each side of the fitting. One of the washers is situated under the banjo bolt head, while the other bolt washer is located between the caliper and the brake line.

Q: How Do I Stop My Banjo Bolt From Leaking?

To stop your banjo bolt from leaking, you need to use a crush washer on each side of the banjo fitting. Crush washers reinforce the seal provided by banjo bolts, and they make it very hard to leak, except when they start wearing off.

There are several types of crush washers, but solid aluminum crush washers seem to be the more popular option as they are known to work well. You might want to try the stat-o-seal style washer if you have not had any luck with metal crushers.

Q: Can You Reuse Copper Banjo Bolt Washers?

Like all mechanical components, the copper banjo bolt washer often fails after a while, and they need to be replaced to prevent system leaks. Some folks get away with reusing copper banjo bolt washers by annealing them. However, what this does is toughen the copper washer and make it difficult to crush subsequently.

Copper banjo bolt washers are best for one-time use because you may not get a good seal if you reuse them. So avoid using them as much as possible.

Final Words:

If you read the article all the way here, you should be able to answer the question how does a banjo bolt work? In case you missed it, here is a quick recap.

Banjo bolt fittings are vital components of most modern vehicles because they transfer highly pressurized fluids that are part of the automotive process.

Banjo bolts are part of the banjo fittings, and they are responsible for their operations. They are hollow bolts that allow fluids to pass through them to the other part of the fitting and onward to the delivery lines in the vehicle.

Learn More:


Hi there, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked as a Mechanic and Mechanic Supervisor for over fifteen years at Global Rebound Automotive companies - Toyota, TATA, BMW, Nissan, TVs, and Others. Now, I enjoy my new role of leading a team of automotive experts (in their respective fields) and publish new content on a regular basis on my website and social media.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts