Can I reuse banjo bolt crush washers?

No. Crush washers deform permanently during tightening to create the seal. Reusing them almost always results in a slow leak. Always fit new washers, which cost only a few pence each.

How tight should a banjo bolt be?

Brake-system banjo bolts are typically torqued to 20–25 Nm. Always check the vehicle manufacturer's specification — over-tightening can crack the banjo fitting, while under-tightening results in leaks.

What thread size is a banjo bolt?

The most common sizes on passenger cars are M10×1.0 and M10×1.25. Turbocharger oil-feed banjo bolts may be M12 or M14. Measure the original or check the part number to confirm the exact size.

Why is my brake calliper leaking after a hose replacement?

The most likely cause is that the crush washers were reused rather than replaced, or one washer was omitted. Undo the banjo bolt, fit two new copper washers, torque correctly, then bleed the brakes.

Are banjo bolts a safety-critical part?

Yes, where they are used in brake or clutch hydraulic circuits. A failed seal can cause fluid loss leading to brake fade or total failure. Inspect and renew washers at every disturbance.

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Banjo Bolt buying guide — what to know before you buy

A banjo bolt is a hollow, drilled fastener used to connect hydraulic lines — most commonly brake hoses, clutch lines, and oil feed pipes — to components such as brake callipers, master cylinders, and turbocharger oil inlets. The bolt passes through a banjo fitting (a circular end fitting on the hose) and clamps it against the component face, sealing via copper or aluminium crush washers on both sides. Corrosion, over-torquing, or reuse of worn washers are the most common causes of hydraulic leaks at banjo connections. CarParts247 stocks banjo bolts and replacement sealing washer kits from Febi, Elring, and Victor Reinz to suit a wide range of European and Asian vehicles.

When to replace a banjo bolt or its sealing washers

Banjo bolts rarely fail on their own, but the soft-metal crush washers that seal each face must be renewed every time the fitting is disturbed. Reusing old washers is a frequent cause of seeping brake fluid or oil leaks that only appear after a repair.

Visible oil or brake fluid seeping from around a hose fitting
Caliper, master cylinder, or turbo oil-feed connection feels damp to the touch
Corroded or cross-threaded bolt threads — replacement is necessary
After any brake hose, clutch hose, or turbo oil-line removal
Crush washer visibly flattened, scored, or no longer circular

Correct fitting technique

Fitting a banjo bolt correctly takes only minutes but requires attention to detail. Using two fresh copper washers — one each side of the banjo fitting — and torquing to specification prevents virtually all post-repair leaks.

Always fit new crush washers; never reuse originals
Brake-system banjo bolts typically torque to 20–25 Nm
Turbocharger oil-feed banjo bolts are often lower — check OE specification
Copper washers can be annealed (heated and quenched) to improve the seal if only copper stock is available
After fitting brakes, pump the pedal to pressure before test-driving

OEM vs aftermarket considerations

OE-grade copper or aluminium crush washers from Elring and Victor Reinz are inexpensive and widely available. Saving money on washers only to have a hydraulic leak that requires bleeding the system again is a false economy. For banjo bolts themselves, ensure the thread pitch and shank length match the original.

Most passenger-car banjo bolts are M10×1.0 or M10×1.25; confirm before ordering
Stainless-steel bolts offer improved corrosion resistance in high-moisture environments
Febi and Elring kits often include both the bolt and the correct washer pair