Customer 
A small fastener can affect the fluid system of any engine. A banjo bolt is an example of a specialised hollow fastener. The purpose of a banjo bolt is to keep the fitting in place but, at the same time, permit the liquid to move through internal channels. The compact design of this fastener makes it useful in diesel fuel systems, motorcycle braking systems, turbocharger oil lines, as well as in other applications where space and location of the liquid path is especially important.
Choosing the wrong bolt may lead to fitment issues or system leaks. The choice must be made based on size, length, internal passage dimensions, use of washers, and equipment compatibility.
Whether you are replacing a leaking connection or upgrading your diesel fuel system, the right banjo bolt specification knowledge will help you select the right hardware for the job.
A banjo bolt is generally a hollow bolt with threads on one or both ends that secure a ring-shaped fluid connection fitting and allow fluid to pass through. Unlike a conventional bolt, it performs two functions: fastening the connection and helping the fluid to travel through it.
It usually consists of three primary parts:
The name “banjo bolt” comes from the ring-shaped design of the fitting, similar to the musical instrument called a banjo. The banjo connection allows a hose to be connected at a suitable angle without rotating the whole hose during the installation.
The bolt includes a central bore and cross-drilled holes that lead from the internal passage to the sides of the fitting. Fluid travels between the attached line and the receiving part through the holes.
The ring fitting goes around the bolt. The washers are placed on the surfaces indicated, and tightening the fitting compresses them to create a fluid-tight connection.
The engaging threads provide the clamping force. The washers and the adjacent surfaces contain the fluid. Correct thread engagement alone is not enough for a good seal.
Banjo fittings are used in the fuel supply, return, or injector connections of certain diesel engines. TrackTech Fasteners lists high-flow fuel banjo bolting in the 1994-2003 7.3L Ford Powerstroke engine and the injector return banjo bolt products for the 2001-2004 6.6L Duramax LB7 engine. These listings show the importance of engine-specific fitment.
A brake banjo bolt is used to connect a flexible brake line to a matching caliper or master cylinder. Some hydraulic clutch systems also have similar connections.
A brake line assembly with a banjo bolt must make sure to withstand hydraulic pressure. In the assembly process, the bolt, fitting, washers, and receiving port must match the vehicle manufacturer’s specifications.
Some turbocharger systems utilize banjo-style connections for the supply of lubricating oil. The internal passage must be compatible with the specified oil-flow requirements of the engine.
Agricultural machinery, construction equipment, and industrial applications may use banjo connections in systems where compact fluid routing is beneficial. Pressure ratings, service temperatures, and fluid compatibility will dictate the choice of assembly.
A standard banjo bolt consists of a hollow shaft, a threaded section, and cross-drilled holes. Usually, it is designed to accommodate a single compatible fitting.
As the name suggests, a double banjo bolt is used to accommodate two compatible fittings at one connection point. It requires a specific receiving port designed for the combined assembly, as well as an appropriate bolt length with a specific seal.
High-flow banjo bolts are characterized by modified flow passages or openings designed to improve flow compared with a particular original design.
TrackTech lists high-flow fuel banjo bolts for select 7.3L Powerstroke engines. However, the actual result will depend on the overall fuel system and its application.
Banjo Bolt sizes differ by manufacturer and equipment. The chart below shows examples for identification when ordering, not as replacement recommendations for all applications.
| Application | Example thread sizes | Sealing arrangement |
|---|---|---|
| Motorcycle and automotive brakes | M10 × 1.0 or M10 × 1.25 on some models | Specified copper or aluminum washers |
| Turbocharger oil connections | M10 or M12 on some designs | Application-specific metal or bonded seals |
| Diesel fuel supply and return | Engine-specific metric or other thread standards | Specified washers or seals |
| Double banjo assemblies | Determined by the receiving port | Washers for each specified sealing interface |
Note: The examples shown are not fitments for any particular application. See original part number, thread pitch, length of bolt, fitting size, washer specifications, and equipment manufacturer’s technical publications for correct replacement part.
Banjo bolt washers create a seal between the two interfaces around the fitting. With the wrong type of seal, fluid can run out of the fitting despite a correctly sized bolt. If you are using the wrong washer for the job, it can allow fluid to escape when the banjo bolt is used in a threaded port.
You must ensure the inner diameter and outer diameter of the washer, the washer’s thickness, its material, and its compatibility with the mating surfaces. Even if the washer fits on the end of the bolt, the bolt may still be unsuitable for the connection.
Washers may be designed for single use only. Follow the manufacturer’s recommendations for replacement washers, especially for brake and fuel systems.
There are quite a few reasons for a leaking banjo bolt:
Take a closer look at the entire connection and not just the bolt, assuming it is defective. If there is a leak of oil or brake fluid, do not allow the machinery to be used until the issue has been fixed.
Make sure to follow the practices for maintaining proper assembly:
It should be noted that there is no common torque value for all banjo bolts. The correct specification depends on the fastener, sealing arrangement, and receiving parts.
Do not identify a thread’s type based only on how it looks. Thus, metric threads specify the diameter and pitch in millimeters, while unified threads measure the diameter in inches and threads per inch as well. UNF stands for Unified National Fine.
To identify what bolt is already available:
Make sure to check the necessary lengths, thread engagement, fitting size, and bore dimensions. A long bolt can hit the bottom, and the wrong internal passage can disrupt system flow.
TrackTech Fasteners distinguishes different applications of Powerstroke and Duramax in their products. Verify engine family, model year, as well as the product description and included hardware before ordering replacement.
Choosing the appropriate banjo bolt starts with matching the component to your engine and fuel-system requirements.TrackTech Fasteners carries a variety of high-flow fuel banjo bolts for select 7.3L Ford Powerstroke applications, as well as injector return banjo bolt products for the 2001-2004 6.6L Duramax LB7.
Learn more about TrackTech Fasteners’ fuel system products and parts so that you know what hardware is in stock and what applications it fits.
No matter what you are looking for, whether you are replacing old equipment or browsing for compatible spares, always research the products you are considering. The right component should match the intended application—not merely look similar to the original.