Emissions System

When your CPV O-ring fails it causes a slow oil leak on the passenger side of the engine, making an oily mess that frequently resembles a rear main seal leak. Replacing the CPV with an upgraded o-ring ensures a long-term solution to this common problem. 

The factory o-ring over time fails from heat cycling and oil exposure due to the Buna rubber used in OEM o-rings, while the included Viton Fluoroelastomer is resistant to a much higher temperature to ensure prolonged life without leaking. 

Restore proper engine ventilation with this premium replacement Crankcase Breather Valve (11127809512).

Designed to match the performance of the original BMW unit (OE 11-12-7-809-512 / 11-12-7-803-790), this valve maintains correct crankcase pressure, helps prevent oil buildup, and supports clean, efficient engine operation.

Crafted from high-quality, long-lasting materials and shaped to replicate the factory design, it installs easily in place of the stock breather without any modifications required.

Whether you’re addressing pressure-related drivability issues, refreshing your engine’s ventilation system, or performing preventative maintenance, this breather valve provides dependable performance and protects your BMW’s engine for the long haul.

Elevate your S63 4.4L engine's capabilities with our meticulously designed Crank Case Vent Hose Kit. Crafted from premium-grade materials, this kit ensures superior ventilation, mitigating pressure accumulation within the engine, thereby enhancing its overall performance.

Engineered to precise specifications, our kit seamlessly replaces the OEM vent hoses, guaranteeing a perfect fit. By reducing stress on the engine, it prolongs its lifespan and maintains peak functionality. Rely on this kit to provide unparalleled performance and unwavering reliability for your S63 4.4L engine.

The rubber hoses and oil separator can crack or become faulty, leading to vacuum leaks or oil leaks. This is caused by the stress the components are exposed to during heating and cooling cycles, especially if the vehicle is not brought up to operating temperature during driving in cold weather climates.

This kit includes the needed hoses, oil separator, mounting grommet, and hardware.

Fits the following BMWs:
1998-2003 E39 BMW M5

The engine crankcase breather hose is a vital part of the Positive Crankcase Ventilation (PCV) system, responsible for directing pressurized air from the engine crankcase to the air/oil separator, also known as the PCV valve. This separator removes oil vapors from the air, allowing the oil to return to the engine while feeding the filtered air back into the intake system to support efficient combustion.

As a byproduct of the combustion process, positive crankcase pressure naturally builds up in the engine. The breather hose operates under constant exposure to heat, pressure, and an air/oil vapor mixture, making it prone to wear and failure over time. Ensuring the breather hose is in proper working condition is crucial for maintaining engine performance, adhering to emissions standards, and preserving the functionality of the PCV system. Promptly replace this component at the first signs of damage or degradation to avoid further complications.

Ensure your BMW engine runs clean and efficiently with this Crankcase Breather Valve Diaphragm Spring and Cap (11127803790).

A direct-fit replacement for the original BMW breather (OE 11127803790 / 11-12-7-803-790), this valve maintains proper crankcase pressure, reduces oil buildup, and promotes smooth engine performance.

Constructed from durable, high-quality materials and engineered to OEM specifications, it installs easily without any modifications.

Ideal for maintenance, resolving crankcase pressure issues, or restoring your engine’s ventilation system, this breather valve delivers reliable performance and helps protect your BMW for years to come.