Variable camshaft control (VANOS)

Functional description, see BMW Service Technology:

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SBT number:

• 11 04 04 097
  

Overview of functions

The double VANOS of the S85 is a high pressure VANOS with oil pressures of up to 90 bar. The oil pressure is created by a separate oil pump. The VANOS oil pump is supplied with oil by the pendulum-slide oil pump.

An calibration unit each with two VANOS gears is fitted for each cylinder bank. Each VANOS gear is adjusted by a solenoid valve. The solenoid valves are activated by the DME. When running at idle, the calibration units are at the maximum positions.

Important!

The VANOS solenoid valves react very sensitively to dirt particles. For this reason, ensure absolute cleanliness when working on the VANOS!

Diagnosis instructions

The calibration of the VANOS is monitored by the DME via the camshaft sensors. Corresponding faults are saved in the diagnostic fault memory.

If the DME detects control deviations or excessively long adjusting times etc. on the VANOS, this can have the following causes:

• VANOS oil pressure too low
  Leaks in the VANOS oil supply or a defective oil pump can lead to a drop in oil pressure. The oil pressure can be checked using a special tool, see repair instructions 11 36 009, 'Checking the oil pressure of VANOS calibration units'.
  Important! During the pressure test on one bank, rough engine operation, misfiring faults and VANOS control faults can occur.
  Acoustic problems on engine start (rattling) are caused by a lack of VANOS oil pressure on engine start. Check the VANOS oil pressure, as well as the pressure accumulator and pressure accumulator valve for leak-tightness.
  
• Jamming solenoid valves
  Solenoid valves can jam due to dirt or metal filings in the oil. It might be possible to eliminate jamming by rinsing with clean oil (oil change).
  Important! In the event of metal filings in the oil, the source of the metal filings must be clarified. Jamming VANOS solenoid valves can indicate the onset of mechanical damage of the jamming was caused by metal filings.
  
• Defective activation of the solenoid valves
  
• Defective O-rings in solenoid valves