low oil pressure BMW 740i 2001 E38 M62TU Engine Workshop Manual

7
M62 TU VANOS COMPONENTS
M62 TU VANOS components include the following
for each cylinder bank:
•New cylinder heads with oil ports for VANOS
•VANOS transmission with sprockets
•Oil distribution flange
•PWM controlled solenoid valve
•Oil check valve
•Camshaft position impulse
VANOS CONTROL SOLENOID & CHECK VALVE:The VANOS solenoid is a two wire,
pulse width modulated, oil pressure control valve. The valve has four ports;
1. Input Supply Port - Engine Oil Pressure
2. Output Retard Port - To rear of piston/helical gear (retarded camshaft position)
3. Output Advance Port - To front of piston/helical gear (advanced camshaft position)
4. Vent - Released oil pressure
A check valve is positioned forward of the solenoid in the cylinder head oil gallery. The
check valve maintains an oil supply in the VANOS transmission and oil circuits after the
engine is turned off. This prevents the possibility of piston movement (noise) within the
VANOS transmission system on the next engine start.

9
M62 TU VANOS CONTROL
As the engine camshafts are rotated by the primary and secondary timing chains, the
ME7.2 control module activates the VANOS solenoids via a PWM (pulse width modulated)
ground signal based on a program map. The program is influenced by engine speed, load,
and engine temperature.
•Shown below: In its inactive or default position, the valves direct 100% engine oil pres-
sure flow to achieve max “retard” VANOS positioning
•Top of next page: As the Pulse Width Modulation (PWM) increases on the control sig-
nal, the valve progressively opens the advance oil port and proportionately closes the
retarded oil port.
Oil pressure pushes the piston toward the advance position. Simultaneously the oil
pressure on the retarded side (rear) of the piston is decreased and directed to the vent
port in the solenoid valve and drains into the cylinder head.
•Bottom of next page: At maximum PWM control, 100% oil flow is directed to the front
surface of the piston pushing it rearward to maximum advance.
Varying the pulse width (on time) of the solenoids control signals proportionately regulates
the oil pressures on each side of the pistons to achieve the desired VANOS advance angle.