All current MINI engines incorporate a pressure–controlled crankcase ventilation system that uses various crankcase ventilation valves, depending on the engine type. Although the valves all look different, they function similarly using a spring and diaphragm assembly to control the crankcase pressure.
A properly functioning pressure control valve is designed to maintain a slight vacuum (underpressure) in the crankcase that ensures reliable cross-case venting during all engine-operating conditions. Some of the causes and results of a malfunctioning crankcase ventilation system are listed below.
Causes of Excessive Overpressure (Pressure)
– Internal engine damage or wear.
– Obstruction in the crankcase ventilation system.
– Defective pressure control valve.
Results of Excessive Overpressure
– Damage to the engine oil seals.
– Increased engine oil consumption (can be misdiagnosed as a defective turbocharger).
– Excessive engine oil in the intake system.
– Excessive engine oil in the charged intake tubes or the intercooler on turbocharged engines (can also be misdiagnosed as a defective turbocharger).
– Engine oil dipstick is dislodged from the guide tube (if equipped).
Cause of Excessive Underpressure (Vacuum)
– Defective pressure control valve.
Results of Excessive Underpressure
– Damage to the engine oil seals.
– Increased engine oil consumption.
– Excessive engine oil in the intake system.
– Rough engine idling or engine misfire.
– Whistling or howling noise from the engine (can be misdiagnosed as a defective turbocharger).
– Increased mixture adaptation values.
Measuring The Pressure
The pressure in the crankcase can be measured with a pressure transducer. Pressure readings can be taken at the oil filler cap. MINI recommends taking an oil filler cap and attaching a plumbing fitting with 3/16” barb and 1/8” NPTF opening.
Specification and actual readings from the vehicle may vary by up to 110%, but not more than 4.0 mBar.
Pressure Specifications:
W10 = 1.0-6.0 mBar
W11 = 2.5-4.0 mBar
N12 = 22 mBar
N14 = 38 mBar
N16 = 36 mBar
N18 = 36 mBar
B36 = 24 mBar
B38 = 24 mBar
B46 = 26 mBar
