Mazda MX-5 Miata Crankcase Breather Hose

The hose provides a passage between components; a PCV valve controls ventilation flow or pressure in the system. Depending on the engine, the valve may be separate or built into another component.

Bank-specific hoses can have different shapes and connections. One A-Premium passenger-side hose is listed for cylinders 1–4 and explicitly excludes cylinders 5–8 on its covered application.

A hose listing does not automatically include a separate valve. Check the selected package and the engine's design if the valve or another ventilation component also needs replacement.

A restriction can increase crankcase pressure and affect oil seals. MINI identifies an obstructed ventilation system among possible causes of excessive pressure; diagnosis should also consider the valve and engine condition.

First confirm the fault has been corrected and the connections are secure. A code can reflect another issue in the ventilation or intake system, so clearing it without diagnosis does not establish a successful repair.