Copper Washers

Copper Washers & Banjo Bolt Sealing Washers

Copper sealing washers for banjo bolt connections on brake, clutch, fuel and turbo oil lines. Sold individually in every common size, so you can buy exactly what a job needs.

Why copper, and why single use

A banjo fitting seals by clamping a soft washer either side of the banjo against the mating faces. Copper is used because it's soft enough to deform and fill the microscopic imperfections in both surfaces, creating a leak-free seal under pressure — brake systems routinely see over 1,000 PSI.

That deformation is permanent. Once a copper washer has been crushed it has already conformed to one specific pair of surfaces and work-hardened in the process. Reusing it is the single most common cause of a weeping banjo joint after a brake hose change. Always fit new washers — two per banjo bolt, one either side of the banjo.

Sizes available

• M8 — for M8 banjo bolts, common on motorcycle and small-bore applications
• 10mm & 3/8" — fits both M10 and 3/8" banjo bolts, the most widely used size on European cars
• 7/16" — for 7/16" UNF banjo bolts, common on classic and race applications
• M12 — for M12 banjo bolts, brake and turbo oil feed use
• 14mm, 16mm and 18mm — for larger banjo bolts on power steering and oil lines

Sizing by the bolt, not the hole

Washer size refers to the internal diameter, which matches the banjo bolt thread diameter — an M10 banjo bolt takes a 10mm washer. If you're unsure, measure the bolt shank rather than the washer you removed, since a crushed washer will have spread.

Also see: banjo bolts, braided brake hose and brake fittings, brake fitting adaptors.