BMW E46/E87/E90/E91/E83/E85 N42/N46 Replacement Crankcase Ventilation Oil Separator & Breather Hose Components – Restore Proper Crankcase Pressure & Help Prevent Oil Leaks | Replaces Part No. 11617503520, 11157513903, 11157503524, 11157503523, 11157533346

Restore proper crankcase ventilation and help protect your BMW diesel engine from excessive internal pressure with this replacement crankcase ventilation valve designed for select BMW E46 3 Series and E39 5 Series vehicles equipped with the M47 diesel engine. The crankcase ventilation valve, commonly referred to as the crankcase breather or oil separator, plays an essential role in regulating crankcase pressure, separating oil mist from engine blow-by gases, and directing crankcase vapors back into the engine's intake system. Maintaining proper crankcase ventilation is particularly important for turbocharged diesel engines, where excessive pressure and oil contamination can contribute to additional engine and turbocharger problems.

As factory crankcase ventilation components age, accumulated oil residue, carbon deposits, and contaminants can restrict the internal ventilation passages and reduce the effectiveness of the oil separation system. A blocked or deteriorated crankcase breather may prevent blow-by gases from escaping the crankcase at the intended rate, allowing excessive internal pressure to develop. Common symptoms include increased engine oil consumption, oil leaks around engine seals and gaskets, excessive oil accumulation in the intake system, blue or gray exhaust smoke, and abnormal crankcase pressure. In more severe cases, restricted crankcase ventilation can interfere with proper turbocharger oil drainage and contribute to oil leakage through the turbocharger.

This replacement crankcase ventilation valve is designed to restore the intended ventilation pathway by allowing crankcase gases to flow through the breather assembly while supporting the separation of suspended oil particles. The oil separation process helps limit the amount of engine oil carried into the intake system, reducing unnecessary oil contamination of the intake piping and related components. Replacing a restricted or malfunctioning breather can help restore normal crankcase pressure regulation, particularly when the original assembly has become clogged or deteriorated from prolonged use.

Designed as a factory-style replacement for the corresponding BMW M47 diesel crankcase ventilation assembly, this component is associated with BMW part numbers 11122249678 and 11127791552. Its intended configuration supports installation at the original crankcase breather mounting location without changing the engine's factory ventilation arrangement. When properly installed and matched to the correct engine application, a replacement breather helps maintain normal crankcase gas circulation and supports the proper operation of the engine's oil separation system.

For aging BMW E46 and E39 diesel models, maintaining the crankcase ventilation system is an important part of long-term engine care. The M47 engine relies on effective crankcase pressure regulation to help protect engine seals, maintain proper oil management, and support the operation of its turbocharger lubrication system. Replacing a worn or restricted breather can help reduce the likelihood of pressure-related oil leaks, excessive oil carryover, and avoidable stress on surrounding engine components.

Key Features

• BMW M47 Diesel Engine Compatibility: Designed for select BMW E46 318d, E46 320d, and E39 520d applications equipped with the original M47 diesel engine and corresponding crankcase ventilation assembly.

• Restores Proper Crankcase Pressure Regulation: Helps maintain the intended movement of blow-by gases out of the crankcase, reducing excessive internal pressure when a restricted or malfunctioning breather is responsible.

• Supports Effective Oil Separation: Helps separate suspended oil mist from crankcase ventilation gases, limiting unnecessary oil carryover into the engine's intake system.

• Helps Reduce Excessive Oil Consumption: Replacing a failing crankcase breather may help address elevated oil consumption associated with poor oil separation or abnormal crankcase pressure.

• Helps Protect Turbocharger Components: Proper crankcase ventilation supports normal turbocharger oil drainage by reducing excessive crankcase pressure that can interfere with the return of lubricating oil to the engine.

• Reduces Pressure-Related Oil Leaks: Maintaining appropriate crankcase pressure can help reduce unnecessary stress on engine seals and gaskets that may otherwise develop or worsen oil leaks.

• Supports Cleaner Intake System Operation: Effective separation of oil mist from crankcase gases can reduce excessive oil deposits in the intake piping and associated ventilation passages.

• Factory-Style Replacement Configuration: Intended to replace the corresponding original BMW crankcase ventilation valve assembly while maintaining the factory ventilation system's intended arrangement.

• Addresses Common Aging-Related Breather Problems: Suitable for replacing an original breather that has developed internal restrictions, damaged ventilation components, deteriorated seals, or reduced oil separation effectiveness.

• Important Preventive Maintenance Component: Inspection and replacement of a deteriorated crankcase breather can help prevent minor ventilation problems from developing into more expensive engine or turbocharger repairs.

Restore the intended crankcase ventilation performance of your BMW M47 diesel engine with a replacement breather valve designed to support proper internal pressure regulation and oil separation. Replacing a restricted or deteriorated crankcase ventilation assembly can help reduce excessive oil contamination, protect engine seals, support turbocharger lubrication, and contribute to improved long-term engine reliability. For older BMW E46 and E39 diesel vehicles, maintaining the crankcase ventilation system is an important step toward preserving dependable engine operation.

FITMENT: BMW E46 3 Series & E39 5 Series M47 Diesel Engines

Compatible with select BMW E46 3 Series and E39 5 Series diesel models equipped with the original M47 2.0-liter four-cylinder turbocharged diesel engine and the corresponding crankcase ventilation configuration.

BMW E46 3 Series Sedan (1998–2003)

• BMW E46 318d – M47 Diesel Engine (2001–2003)
• BMW E46 320d – M47 Diesel Engine (1998–2001)

BMW E46 3 Series Touring (2000–2003)

• BMW E46 318d Touring – M47 Diesel Engine (2002–2003)
• BMW E46 320d Touring – M47 Diesel Engine (2000–2001)

BMW E39 5 Series Sedan (2000–2003)

• BMW E39 520d – M47 Diesel Engine (2000–2003)

BMW E39 5 Series Touring (2000–2003)

• BMW E39 520d Touring – M47 Diesel Engine (2000–2003)

These applications correspond to BMW parts-catalog listings for crankcase breather part number 11127791552, which supersedes the earlier 11122249678 assembly. Production dates and compatibility can vary by market and specific vehicle configuration. Exact fitment should be confirmed using the vehicle identification number (VIN) and original BMW part number.

Engine Compatibility

• BMW M47 Diesel Engine Family
• BMW M47D20 (204D1): 1,951 cc four-cylinder turbocharged diesel engine used in applicable BMW E46 and E39 models.
• BMW M47 318d: Select 115–116 HP applications.
• BMW M47 320d: Select 136 HP applications.
• BMW M47 520d: Select 136 HP applications.

OEM Replacement Part Numbers

• 11122249678
• 11127791552

BMW Part Number Supersession

• 11122249678: Earlier BMW crankcase ventilation breather part number.
• 11127791552: Later BMW replacement part number that supersedes 11122249678.

Important Engine Compatibility Information

This replacement assembly is associated with the original BMW M47 diesel engine configuration. The later M47TU/M47N engine family can use different crankcase ventilation components and should not automatically be considered compatible.

BMW E46 320d vehicles equipped with the later 150 HP M47TU engine require separate verification, as the engine's ventilation assembly may differ from the original 136 HP M47 application.

Compatibility should be verified through the original BMW part number rather than relying exclusively on the vehicle model, engine displacement, or production year.

Installation

• Factory-style replacement crankcase ventilation valve for compatible BMW M47 diesel engines.
• Professional installation is recommended to ensure correct fitment, sealing, and crankcase ventilation operation.
• Allow the engine to cool completely before beginning the replacement procedure.
• Locate the original crankcase ventilation breather assembly mounted at the upper engine cylinder head cover area.
• Remove any necessary engine covers, intake ducting, or surrounding components required to access the original breather assembly.
• Inspect the surrounding ventilation connections and intake components for oil accumulation, deterioration, or other signs of crankcase ventilation problems.
• Carefully remove the original breather housing mounting hardware and disconnect any associated ventilation connections as required.
• Remove the existing crankcase ventilation valve assembly while preventing dirt, debris, or loose contaminants from entering the engine.
• Inspect the original breather assembly for accumulated oil sludge, blocked passages, damaged sealing components, or signs of restricted ventilation.
• Compare the replacement assembly with the original component to confirm the correct mounting configuration, housing shape, connection points, and sealing arrangement.
• Inspect the sealing surfaces and remove any accumulated residue or debris before installing the replacement component.
• Replace the necessary sealing gaskets or O-rings according to BMW service documentation. Confirm whether these components are included with the replacement assembly before installation.
• Position the replacement crankcase ventilation valve at the original mounting location and ensure all sealing components are properly seated.
• Reinstall the mounting hardware using the correct BMW tightening specifications for the specific engine and assembly.
• Reconnect any ventilation connections and reinstall the surrounding intake components or engine covers removed during the procedure.
• Inspect the ventilation system for disconnected hoses, restricted passages, damaged connections, or other conditions that could affect crankcase pressure.
• Start the engine and check for abnormal operating noises, visible oil leaks, or signs of improper crankcase ventilation.
• Verify normal engine operation and inspect the surrounding breather connections after installation.
• If excessive oil consumption, crankcase pressure, or exhaust smoke continues, further inspection of the turbocharger, engine seals, ventilation passages, and internal engine condition may be necessary.

Crankcase ventilation replacement is primarily a mechanical maintenance procedure and does not ordinarily require engine control module programming or electronic calibration. Exact removal procedures, gasket requirements, and tightening specifications should be confirmed using the appropriate BMW service documentation.

Compatibility Notes

• Confirm Your BMW Engine Code: Verify that your vehicle is equipped with the original M47 diesel engine before ordering. BMW produced several M47 engine variants with different mechanical configurations.

• Verify the Original BMW Part Number: Confirm that your existing crankcase ventilation assembly corresponds to BMW part number 11122249678 or its superseding replacement number 11127791552.

• Original M47 vs. M47TU/M47N Engines: Not all BMW vehicles equipped with an M47-family diesel engine use the same crankcase breather. Later M47TU/M47N applications may have different oil separator housings, mounting arrangements, and replacement part numbers.

• Check BMW 320d Production Dates: Earlier E46 320d models equipped with the original 136 HP M47 engine differ from later 150 HP M47TU applications. Confirm the exact engine configuration before purchasing.

• Inspect the Original Breather Assembly: Compare the replacement valve's housing dimensions, mounting locations, ventilation connections, and sealing surfaces with the existing component to ensure proper installation.

• Confirm Included Components: Replacement crankcase ventilation assemblies may be sold with different combinations of breather housings, oil separator elements, gaskets, seals, and mounting hardware. Verify the actual package contents before ordering.

• Crankcase Pressure Problems Have Multiple Causes: Excessive crankcase pressure can result from a blocked breather, restricted ventilation passages, or increased combustion blow-by caused by worn internal engine components. Replacing the breather will not correct excessive blow-by originating from mechanical engine wear.

• Excessive Oil Consumption Requires Diagnosis: Increased oil consumption may be associated with a malfunctioning oil separator, but it can also result from worn piston rings, turbocharger problems, leaking engine seals, or other lubrication-system issues.

• Inspect the Turbocharger System: A restricted crankcase breather can interfere with turbocharger oil drainage and contribute to oil leakage into the intake or exhaust. However, turbocharger oil leakage can also originate from unrelated turbocharger or oil-return problems.

• Exhaust Smoke May Have Other Causes: Blue or gray exhaust smoke can indicate engine oil entering the combustion process, but it does not automatically confirm crankcase ventilation failure. Turbocharger seals, internal engine wear, and other mechanical problems should be considered during diagnosis.

• Inspect Engine Seals and Gaskets: Excessive crankcase pressure can contribute to oil leaks around aging engine seals and gaskets. Replacing the breather may correct the underlying pressure issue, but already damaged seals may still require separate replacement.

• Check Intake System Oil Accumulation: Some oil mist inside a diesel engine's intake system can be normal. Excessive accumulation should prompt inspection of the crankcase ventilation assembly, turbocharger, and related intake components.

• Crankcase Breather Maintenance: Diesel crankcase ventilation components can accumulate oil residue and combustion-related contaminants over time. Periodic inspection is recommended, particularly on older engines or vehicles exhibiting increased oil consumption or pressure-related symptoms.

• Confirm Vehicle Market Compatibility: Although this component is associated with European-market BMW E46 and E39 diesel applications, compatibility should be confirmed using the VIN and applicable BMW parts catalog for the vehicle's original market and equipment configuration.

• Verify Fitment Before Purchasing: For the most accurate compatibility confirmation, compare the original crankcase ventilation valve with the replacement assembly and check both BMW part numbers against the vehicle's VIN.

Maintaining a properly functioning crankcase ventilation system is particularly important for older BMW M47 turbocharged diesel engines, where restricted ventilation can contribute to excessive crankcase pressure, oil leaks, and turbocharger lubrication problems. BMW service information also identifies inspection of the crankcase ventilation system as an important consideration when diagnosing certain M47-family turbocharger failures. Replacing a deteriorated breather with the correctly matched component helps maintain proper oil separation, supports normal crankcase pressure, and contributes to the long-term reliability of the engine and its surrounding components. 

Please refer to the “Fitment” section in the product description for compatibility details.