BMW 3 Series E90 320d N47 2.0d 177bhp — Excessive Oil Consumption / PCV Valve Failure
The N47 engine can consume significant amounts of oil due to a blocked Positive Crankcase Ventilation (PCV) breather, forcing oil past the turbo seals or piston rings.
Severity
ModerateDIY Difficulty
Moderate
Est. Cost
£150–£400
OBD Codes
None
Engine
Typical layout and location for the Engine assembly.
Symptoms
- Oil top-up warning light every 1,000 miles
- Blue smoke on acceleration
- Oil pooling in the intercooler and intake pipes
- Rough idle
Root Cause
The PCV breather unit separates oil mist from crankcase gases. When it blocks, crankcase pressure rises, forcing oil out through the path of least resistance (usually turbo seals or rings).
How To Fix
- Check PCV valve assembly integrated into the rocker cover
- Replace PCV breather unit (£50-80 parts)
- Check intercooler for oil pooling and drain if necessary
- If consumption persists, turbocharger seals may have failed
Estimated Repair Costs
| Repair Option | Est. Cost (GBP) |
|---|---|
| DIY (parts only) | £60–£160 |
| Independent Garage | £150–£400 |
| Main Dealership | £240–£640 |
Other Faults on This Variant
N47 Timing Chain Failure (Rear of Engine)
CriticalThe BMW N47 diesel engine has a timing chain positioned at the REAR of the engine, against the bulkhead. Chain failure is catastrophic, and repair requires engine removal. This is the most significant known fault in the BMW 3 Series range.
Swirl Flap Failure and Engine Ingestion
CriticalThe N47 intake manifold has metal swirl flaps on actuator rods. When the rods corrode and snap, the flap breaks off and gets ingested into the engine, causing severe internal damage.
EGR Cooler and Valve Failure
ModerateEGR cooler failure on the N47 is common from 70,000 miles. Coolant leaks into the intake manifold and the EGR valve sticks, causing power loss and rough running.
Disclaimer: Repair cost estimates are indicative and based on community data. Always get a quote from a qualified mechanic before proceeding with any repair.