BMW N47 & N57 2.0d/3.0d Crankcase Breather Pipe & Intercooler Boost Hose Failure: Oil Mist Leaks, Whistling & OEM Replacement Guide (13717803842 / 13718512014)

1. Why BMW N47 & N57 Intake Breather Pipes & Cold-Side Boost Hoses Fail Between 60,000 and 95,000 Miles

On BMW's 2.0-litre four-cylinder (N47D20A, N47D20C, N47N, N47S1) and 3.0-litre six-cylinder (N57D30) common-rail turbodiesels, closed crankcase ventilation (CCV) gases exit the rocker cover pressure-regulating valve and feed directly into the clean air intake duct just upstream of the VNT turbocharger compressor wheel.

Because these gases carry hot 95°C–110°C synthetic oil vapour mixed with soot blow-by, the factory polyamide corrugated breather tube (OEM 13717803842) and the adjoining rubber-to-plastic intake boot (OEM 13718508047 / 13718512249) suffer two simultaneous failure modes:

• Thermal Crystallisation of the Squeeze-Lock Ears: Repeated heat soak underneath the foam-lined BMW acoustic engine cover turns the thin corrugated ribs brittle. The moment a technician flexes the main airbox-to-turbo duct during an air filter service, the breather pipe hairline-cracks along the lower bellows fold.
• Elastomer Swelling in the Lip Seal & Cold-Side Intercooler Couplings: Engine oil mist pools at the lowest point of the intake pipe and migrates through the turbo into the cold-side charge air hose (OEM 13718512014 / 13717823517). Standard factory nitrile seals soften, allowing pressurized boost air to hiss past the quick-connect collar under load while weeping black oil onto the undertray.

2. Real Symptoms & BMW ISTA-D / OBD2 Fault Codes to Look For

Before ordering parts, hook up a diagnostic scanner capable of reading BMW DDE (Digital Diesel Electronics) hex codes alongside standard OBD2 P-codes:

3. Crucial Fitment Difference: Early N47 (13717803842) vs Technical Update N47N / F-Series (13718512014 & 13718508047)

One of the biggest mistakes DIYers and general factors make is ordering the wrong intake breather revision. BMW changed the intake architecture when transitioning from the 177 bhp E-Series N47 to the 184 bhp / 218 bhp N47N (N47T) fitted to F10, F11, F30, F31, F32, and X3 F25 chassis:

4. Direct-Fit OEM-Spec BMW N47 & N57 Replacement Parts (In Stock at Our Birmingham UK Warehouse)

All intake, breather, and oil cooler assemblies below are manufactured with oil-resistant fluorocarbon (FKM/Viton) internal lip seals and dispatched same-day from our Birmingham distribution hub with free UK tracked delivery:

SKU: BD1018 • OEM 13717803842

BMW N47 & N57 Crankcase Air Intake Breather Hose Pipe with Seal

Direct squeeze-lock replacement with upgraded oil-resistant gasket for 1, 3, 4, 5, 6, 7 Series & X1/X3/X5.

£18.90 View Part →

SKU: BD1019 • OEM 13718508047

BMW 5 Series F10 / F11 (518d 520d 525d) Air Filter Box to Engine Hose

Complete flexible bellows intake duct for N47N 5 Series models suffering from torn pleats or loose breather necks.

£56.95 View Part →

SKU: BD1020 • OEM 13718512249

BMW N47N Hard Plastic Airbox-to-Turbo Inlet Pipe 4-Piece Kit

Includes hard turbo inlet duct, resonator chamber, breather link & seals for F30, F10 & X3 F25 2.0d.

£35.62 View Part →

MASTER KIT • OEM 13718512014

BMW N47N / N47S1 Complete 3-Piece Air Intake & Breather Assembly Kit

Complete master workshop bundle for F10, F30 & F25—replaces every brittle plastic duct and seal in one go.

£109.25 View Master Kit →

5. Step-by-Step Workshop Replacement & Torque Specifications (45-Minute Job)

Tools Required: 1/4-inch ratchet, E10 Female Torx socket, 7mm & 8mm hose clamp nut driver, flat-blade pick tool (for Henn spring clips), brake & clutch cleaner, and clean lint-free workshop blue roll.

1. Lift the Acoustic Engine Cover Safely: Pull the front of the BMW acoustic cover straight upwards off its rubber ball-studs, then slide it forward out of the rear bulkhead grommets. Mechanic Tip: Check the underside foam insulation—if it is soaked in black diesel oil above the turbo side, your breather hose has been misting for thousands of miles.
2. Disconnect the MAF Sensor & Release the Airbox Duct: Unclip the grey secondary locking tab on the Bosch MAF plug before pressing the release latch. Slacken the 7mm worm-drive clamp at the air filter housing outlet and the E10 Torx support bracket bolt anchored to the cylinder head/manifold support.
3. Release the Crankcase Breather Squeeze-Lock Collar: Squeeze the two serrated oval release tabs on 13717803842 simultaneously and pull straight back off the rocker cover stub. Never pry the rocker cover plastic spigot with a screwdriver—if you snap the spigot off the cam cover, you're looking at a full rocker cover replacement!
4. Degrease the Turbo Compressor Inlet Spigot & Swirl-Flap Plug: Wipe out any pooled engine oil inside the aluminium turbocharger mouth using lint-free cloth dampened with brake cleaner. Spray electrical contact cleaner into the swirl-flap actuator connector directly underneath. (While inspecting the nearside of the block, also check the BMW N47 Oil Filter Housing & Cooler Assembly 11428596283, as oil filter housing gasket leaks frequently run down the block and mimic breather leaks.)
5. Install the New Breather & Intake Duct with Correct Torque: Smear a thin film of clean 5W-30 LL-04 engine oil onto the new internal FKM O-rings. Push both ends of the new breather hose home until you hear a sharp mechanical "click"—tug gently to verify both locking ears are seated behind the collar ridge. Tighten the E10 bracket bolt to 8.0 Nm and the stainless worm-drive hose clamps to 3.5 Nm (do not over-torque onto plastic spigots).
6. Reset MAF & EGR Adaptations via ISTA-D / Launch / Autel: Clear fault codes 290900 and 244C00, then run the "Reset Air Mass Flow Sensor Adaptations" service function so the DDE immediately re-learns clean airflow values without the unmetered air leak.

6. Master Mechanic's Frequently Asked Questions (BMW N47 & N57 Breather & Boost Pipes)