Oil Pressure Relief Valve Screw - Type 4, Waterboxer (Original Style)

This oil pressure relief screw is a correct replacement for the original slotted-head relief plug used on a wide range of Volkswagen engines. It fits the oil pressure relief valve bore in the crankcase and is designed to be tightened and removed using a flat-head screwdriver, just as Volkswagen intended from the factory.

The oil pressure relief system controls maximum engine oil pressure. Inside the crankcase, the relief screw retains a spring and piston. When oil pressure rises beyond the designed limit—such as during cold starts—the piston opens against the spring, allowing excess pressure to bypass safely. This protects the oil cooler, seals, and internal engine components from damage caused by over-pressure.

Over time, original relief screws can become damaged, chewed up by incorrect tools, corroded, or rounded off, making servicing difficult. Replacing the screw restores proper serviceability and ensures the relief valve components are securely retained and sealed.

Features

• Original-style slotted head

• Uses a flat-head screwdriver for fitting and removal

• Correct thread and profile for factory oil pressure relief systems

• Ideal for rebuilds, servicing, or replacing damaged originals

Fitment

Suitable for the following engines:

• Baywindow Buses with Type 4 aircooled engines

  • 1700cc

  • 1800cc

  • 2000cc

• Type 25 / T3 Buses with:

  • 1600cc aircooled CT engines

  • 2000cc aircooled engines

  • 1900cc Waterboxer engines

  • 2100cc Waterboxer engines

Fitting notes / related parts

• Always inspect the oil pressure relief spring and piston for wear or scoring when replacing the screw

• Ensure the bore is clean before refitting

• Tighten securely but do not overtighten to avoid crankcase damage

This is a small but vital component that plays a major role in maintaining correct oil pressure and long-term engine reliability.