51 24 ... Instructions for automatic rear lid actuation (electrohydraulic/fully automatic)

WARNING: This page is about a different car, the 2008 BMW 535xi. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: When working on the opened hydraulic system:
Move rear lid into SERVICE POSITION
System must not be started up.
Adhere to the utmost cleanliness.
Even the smallest of dirt particles in the hydraulic system can cause malfunctions.
If necessary, join hydraulic lines together.
Seal off hydraulic unit.
The hydraulic unit may no longer be activated when the hydraulic cylinder is removed (cylinder extended).
Piston rod must be protected against damage.

Opening and closing rear lid:

NOTE: If a control button is operating again during an opening or closing procedure, this procedure is stopped. When operated again, this changes the direction of the rear lid (except passenger compartment button, opening only here).

Actuation of rear lid is only possible via:

INSTRUCTIONS FOR AUTOMATIC REAR LID ACTUATION

control button in passenger compartment	opening only
control button on outside of rear lid when vehicle is unlocked	opening and closing
remote control button (RCB) on key	opening only
continuous pressing of RCB on key	closing
control button on pull handle in rear lid trim	closing and opening

Anti-repeat device:

An anti-repeat device is fitted to prevent the hydraulic control unit from overheating.

The total motor running time of the hydraulic control unit is recorded by a counter. If the motor is not activated, this counter is reduced by a third of the pause time. A new actuation will not be accepted if the counter exceeds a total running time of 2 minutes. Thus, for a motor running time exceeding 2 minutes, an enforced pause which is three times as long is engaged.

After a cooling-down period of 6 minutes, it is again possible for the motor to run for 2 minutes.

NOTE: However, an actuation which is in operation is not terminated even if the maximum running time is exceeded.

"Rear lid open" end position:

The position of the hydraulic cylinder is measured by the travel sensor.

The control unit loses the end position if the battery voltage is <9 V or in the event of a voltage interruption at the control unit or battery. The next time the rear lid is actuated, the hydraulic unit runs for 13 seconds (regardless of the rear lid setting) in the "Open" direction and stores this setting in the control unit.

The end position is stored the next time the rear lid is actuated.

Installation location of individual hydraulic components:

Hydraulic cylinder:

Hydraulic cylinder (1) is located at rear left in place of gas-filled shock absorber.

Travel sensor (2) is secured to hydraulic cylinder (1).

Fig 1: Identifying Sensor And Hydraulic Cylinder

Courtesy of BMW OF NORTH AMERICA, INC.

Hydraulic unit:

Hydraulic unit (1) is located behind left wheel arch trim in luggage compartment.

Control unit for automatic rear lid actuation is fitted above spare wheel.

Fig 2: Identifying Hydraulic Unit

Courtesy of BMW OF NORTH AMERICA, INC.

Holding function:

The rear lid is held open in the upper opening angle range by the fluid column. This is achieved by check valves in the hydraulic unit. If it remains open for an extended period of time, the rear lid may drop a little. The rear lid does not remain in the end position after manual opening and extended non-use of the automatic function. The fluid is forced out of the lines with the rear lid is manually operated repeatedly. The holding function diminishes, causing the rear lid to drop.

Emergency rear lid operation:

If the automatic facility fails, the rear lid can be opened and closed manually without the need for supplementary measures.

The expenditure of force for emergency operation is greater than in the version with two gas pressure dampers.

Emergency operation is determined by:

Switching pressure of emergency valve (mechanical-hydraulic pressure limiting valve)
Flow resistance of fluid in the lines, thus manual force increases with increasing actuating speed

Checking fluid level in hydraulic unit:

IMPORTANT: Only the hydraulic fluid from the small parts kit may be used.

Test requirements:

Open rear lid (motor-driven) once and close again, this bleeds the system.

Open rear lid again (motor-driven).

Remove HYDRAULIC UNIT .

Set hydraulic unit (1) according to installation position in vehicle with equipment carrier down on a horizontal surface.

Correct fluid level must be in area A of marking (2).

Fig 3: Removing Hydraulic Unit