A banjo bolt is a type of fasteners that is used in hydraulic systems. A banjo bolt is specifically designed to allow for fluids to be contained within the bolt, but also to allow for those fluids to flow through the bolt. A hole is drilled through the shaft of the banjo bolt to allow for the fluids to pass through the bolt.
In order to prevent those fluids from flowing out of the system, a banjo bolt contain two crush washers that are placed on either side of a banjo eyelet. When the technician tightens the banjo bolt, the washers is compressed against the banjo eyelet which prevents the fluids from leaking out of the system. If the wrong type of washers are used, or if the washers are not fresh when they are installed into the banjo bolt, the fluids will leak from the system.
What a banjo bolt is and how to install it
In order to properly install a banjo bolt, the components should be placed in the following order: one of the crush washers should be placed against the port into which the banjo bolt will be installed. The technician should place the banjo eyelet against the banjo bolt, followed by the second crush washer that will be placed against the head of the banjo bolt. It is essential that the washers are placed in this order so that the washers will be compressed between the banjo eyelet and the port.
Additionally, a torque chart should be followed to ensure that the banjo bolt is tightened to the proper amount of torque. For instance, steel banjo bolts with a grade of 8.8 or 10.9 are the most common type. In these instances, specific amount of torque must be applied to the steel banjo bolt to ensure proper sealing of the system.
However, if an aluminum banjo bolt is used, the torque should be reduced by 20 to 30 percent because aluminum is a softer metal then steel. Crush washers are used to prevent leaks in banjo bolts. Crush washers can be made of a variety of different materials.
Copper washers are often used in brake systems and turbocharger oil feeds because copper is able to withstand higher amounts of heat than other metals. Aluminum washers are often used in fuel line. However, aluminum crush washers should never be reused.
Crush washers that are made of aluminum lose its ability to seal if they are compressed once. Bonded Dowty washers are another type of crush washer that include a rubber O-ring that is built into the washer. These washers are more forgiving than copper washers but they, too, must be installed according to a specific amount of torque.
If the incorrect type of crush washer is used in a banjo bolt system, that system will leak. Banjo bolts are used in a variety of different mechanical systems and devices. For example, many people utilize banjo bolts in their brake systems.
Banjo bolts are used in motorcycle and car brake systems. Additionally, banjo bolts are often used in turbocharger oil feeds. Banjo bolts are available in a variety of size ranging from M10 for motorcycles to M16 for heavy machinery.
Single banjo bolts contain one eyelet and two washers while double banjo bolts contain two eyelets and three washers allowing for two lines of fluid to be fed into a single port. Banjo bolts need to be installed following a specific process in order to properly function. The threads and the holes into which the banjo bolt will be installed should be cleaned using brake cleaner.
The technician should then hand-thread the banjo bolt into the port to ensure that the threads are not cross-threaded. The banjo bolt should then be tightened to the proper amount of torque using a calibrated torque wrench. After the banjo bolt is torqued to the proper amount, the hydraulic system should be bled and the banjo bolt should be wiped down with a clean rag.
Should there be any liquid on the banjo bolt, the installation may not have been completed properly. For example, if the banjo bolt is under-torqued, the system will weep fluid. In this case, the bolt should be re-torqued.
If the bolt is over-torqued, it is possible that the bolt snapped or that the eyelet was crushed enough to prevent fluid from flowing through the system. Additionally, if the banjo bolt was cross-threaded when it was installed, the threads may need to be repaired. Many times, if there is a leak in a banjo bolt system, it is because an old and used crush washer was used.
In these instances, the crush washer should of been replaced with a new one each time the banjo bolt is installed. Finally, it is essential that the torque specification be verified according to the vehicle or machine’s service manual.
