In modern engines, numerous hoses and tubes connect fluids back and forth between various engine parts. The pieces that hold these hoses in place are called banjo bolts. These specialized hardware bolts tend to be easy to use, but can cause problems if they are tightened in the wrong way.
Function
A banjo bolt works the same way as a regular screw bolt with a hole going through the bolt body. Fluids then flow through the cavity. Banjo bolts are commonly used on hydraulic brake hose linkages. The bolt keeps a brake line end connected to a caliper while still allowing the fluid to get through to the brake pads.
Effects
When a banjo bolt gets overtightened, it constricts the hose eye it penetrates. Because the bolt hardware substance involves metal, the edge of the bolt will eventually cut into the hose eye ring. This in turn causes a break in the hose eyelet and an eventual leak that will disrupt the flow.
Considerations
The whole purpose of a banjo bolt is to keep a tight grip on the hose it holds in place. If the hardware sits loose, tension and movement will eventually cause the hose to pull free and cause a gap. The system flow will be completely disrupted, and the fluid will spill out.
