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Pelican Technical Article:

Convertible Top

Nick Czerula

Time:

2 hours2 hrs

Tab:

$300

Talent:

**

Tools:

Plastic prying tool, Door panel clip tool, flathead & Phillips screwdriver

Applicable Models:

Z4 M54 (2003-05)
Z4M S54 (2006-06)
Z4 N52 (2006-06)
M3 (N/A-A)

Parts Required:

Compartment base, compartment adjusters, hall sensor

Hot Tip:

Keep top clean

Performance Gain:

Remedy convertible top issues

Complementary Modification:

Replace convertible top motor

Interior trim pieces in BMW Z4 cars are often made of preformed hard plastic. Plastic clips or metal screws are used to hold them in place. To avoid marring the trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out trim panels, switches or electrical accessories.

The Z4 is available with two convertible options, manual and fully automatic. The "Z" folding action means that the front roof bow simultaneously acts as the stowage compartment cover when the top is lowered. This further simplifies operation of the convertible as there is no separate stowage compartment cover to be moved. Consequently, there is no need for a top cover as in earlier BMW convertibles.

The manual convertible is raised and lowered by hand (once unlatched) with the help of hydraulic gas cylinders.

The top lowers and raises fully automatically by means of electrohydraulic servo units that control the primary soft-top movements. The top / windshield top rail locks are operated by an electric motor. The top is raised and lowered by pressing the top switch located in the center console.

The hydraulic pump is mounted to the left side of the top main pivot. It is an electric motor driven hydraulic pump with integrated valving. One unit runs it all.

The operation of the pump and locking mechanism are controlled by the convertible top module (CVM) as requested via switch input. A temperature sensor protects the hydraulic pump unit against overload. There is a temperature sensor fitted to the hydraulic pump unit. At a temperature of 105 degrees C the pump is prevented from operating in order to protect the hydraulic system from damage. The soft-top can then only be operated manually. The pump hydraulic fluid can't be topped up or replaced. The pump can be replaced by removing the top from the vehicle. It is self-bleeding by repeating top opening and closing.

Before the top can be opened or closed, the following conditions must be met:

1. Neither window detected as closed by the basic module

2. Vehicle stationary

3. No hardtop installed

4. Ignition key position at terminal R at least (except for Easy Open/Close function)

5. System test reports no faults

6. No short circuit and no circuit break present

7. Outside temperature is above minimum limit

Sequence:

1. Windows are lowered (window regulators are operated for 1.5 seconds if a closed window is detected)

2. Top is released from the windscreen top rail

3. Top is folded backwards

4. Top is stowed in stowage compartment and locked in place

5. Locking latches are retracted while pump is still running

6. Red LED goes out

7. Windows are raised (2 seconds after soft-top locks in position)

Raising the top

Sequence:

1. Windows are lowered (window regulators are operated for 1.5 seconds if a closed win dow is detected)

2. Locking latches are extended and the stowage compartment catch is released

3. Soft-top is lifted out of stowage compartment

4. Soft-top is raised forwards

5. Locking latches engage in windscreen top rail

6. Locking mechanism is activated, moves to "LOCKED" position and stops on reaching the limit switch

7. Red LED goes out

8. Windows are raised (2 seconds after soft-top locks in position)

Note: If the soft-top button is released while the raising or lowering sequence is still in progress, the movement of the top comes to an immediate halt. Because the drive system does not lock, the top is then held only by the inherent resistance within the mechanism and the hydraulic servo units. Pressing the button again restarts movement.

Easy Open / Close function

An automatic sequence for the top can be activated using the ignition key in the driver door.

Sequence:

1. Insert ignition key in driver door lock

2. Turn key anti-clockwise and hold. The basic module immediately sends the "Easy Open" signal to the soft-top module.

3. The window regulators are then operated by the CVM control unit within 1.5 seconds.

Windows are lowered

4. Remaining sequence as for "Lowering the soft-top", steps 2 to 7

Easy Close sequence:

1. Insert ignition key in driver door lock

2. Turn key clockwise and hold. The basic module immediately sends the "Easy Close" signal to the soft-top module

3. Remaining sequence as for "Raising the soft-top", steps 2 to 7

4. The window regulators are then operated by the CVM control unit within 1.5 seconds. Windows are closed.

5. Remove ignition key from door

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

The Z4 is available with two convertible top (red arrow) options, manual and fully automatic.
Figure 1

The Z4 is available with two convertible top (red arrow) options, manual and fully automatic. The "Z" folding action means that the front roof bow simultaneously acts as the stowage compartment cover when the top is lowered. This further simplifies operation of the convertible as there is no separate stowage compartment cover to be moved. Consequently, there is no need for a top cover as in earlier BMW convertibles.

The top lowers and raises fully automatically by means of electrohydraulic servo units that control the primary soft-top movements.
Figure 2

The top lowers and raises fully automatically by means of electrohydraulic servo units that control the primary soft-top movements. The top / windshield top rail locks are operated by an electric motor. The top is raised and lowered by pressing the top switch located in the center console (red arrow).

If water is leaking into your passenger cabin, check if the drains are clogged.
Figure 3

If water is leaking into your passenger cabin, check if the drains are clogged. Remove the rear wheel well liners. See our tech article on rear wheel well liners removing. Then locate the drain (red arrow) just above the wheel speed sensor connector housing near the trailing arm bushing mount. Pull the drain straight out (inset).

Clear any debris (red arrow) from the drain and reinstall it.
Figure 4

Clear any debris (red arrow) from the drain and reinstall it.

The hydraulic pump is mounted to the left side of the top main pivot.
Figure 5

The hydraulic pump is mounted to the left side of the top main pivot. It is an electric motor driven hydraulic pump with integrated valving. One unit runs it all. This photo shows the top removed with a faulty (corroded) hydraulic pump. It will have to be replaced as a unit. This is a complicated repair that requires many special tools. Beyond the scope of this article. I suggest getting a repair manual if you need to remove it.




The soft-top can only be lowered when the stowage compartment base is at its lowest position.
Figure 6

The soft-top can only be lowered when the stowage compartment base is at its lowest position. The base has a microswitch (red arrow) that monitors its position, preventing the top from opening when in the upper position. The stowage compartment base can be moved to the upper or lower position by turning the adjuster handles. Gas dampers incorporated in the two stowage compartment base mechanisms hold the stowage compartment base at the respective limits of movement. Switch shown with storage compartment lid removed.

If the top won't lower or raise check the switch first.
Figure 7

If the top won't lower or raise check the switch first. I have found a few shelves jammed in the up position and a few storage trays misaligned with the switch channel. Red arrow is pointing to the storage tray pin (red arrow) not riding in the switch slot correctly.

If the electrics or hydraulics fail, the top can be raised / lowered by means of the emergency actuator.
Figure 8

Emergency Closing and Opening
If the electrics or hydraulics fail, the top can be raised / lowered by means of the emergency actuator.
To raise the top using the emergency actuator:
- Open bypass circuit on hydraulic pump unit by pulling cable.
- Release soft-top stowage compartment catch by pulling cable.
- Raise soft-top to windscreen top rail by hand.
- Engage windscreen top rail lock using Allen key.
For lowering the soft-top with the emergency actuator, the procedure is reversed.
Opening bypass circuit on hydraulic pump unit:
In the trunk on the left side below the top stowage compartment base there is a release cable with a plastic pull handle (red arrow). The plastic pull handle is pulled out as far as it will go and then locked in that position by turning it through 90 degrees (inset). This opens a bypass circuit in the hydraulic pump unit. The soft-top can then be moved by hand.

Emergency stowage compartment catch release.
Figure 9

Emergency stowage compartment catch release. The top stowage compartment catch must then be released. This involves pulling the release cable on the rear trunk trim panel. The soft-top stowage compartment catch then disengages. The release cable is on the trunk bulkhead (red arrow). Pulling the release cable handle
from inside the trunk releases the top stowage compartment catch (inset). The soft-top can then be raised up to the windscreen top rail by hand.

To lock the soft-top to the windscreen top rail, the plastic trim on the front roof bow has to be removed.
Figure 10

Operating the windscreen top rail lock manually:
To lock the soft-top to the windscreen top rail, the plastic trim on the front roof bow has to be removed. Below the plastic trim panel is an Allen head bolt (red arrow). Using the Allen key supplied in the vehicle toolkit, the windscreen top rail lock can then be locked or unlocked manually.

The Hall-effect sensors detect the top position when it is fully raised or fully lowered.
Figure 11

The Hall-effect sensors detect the top position when it is fully raised or fully lowered. The two sensors are located at the left-hand main pivot. Hall-effect sensor 1 ( red arrow) signals to the Soft-top module 4 that the fully automatic soft-top is in the fully raised position. Hall-effect sensor 2 (blue arrow) signals to the Soft-top module 4 that the fully automatic soft-top is in the fully lowered position in the stowage compartment.

An advanced scan tool can display top position.
Figure 12

An advanced scan tool can display top position. Usually open or closed. If implausible is displayed (red arrow), the top is either not fully up or down.

A quick test for the Hall-effect sensors is to monitor top position and use a socket extension to activate the sensor (red arrow).
Figure 13

A quick test for the Hall-effect sensors is to monitor top position and use a socket extension to activate the sensor (red arrow). When the switch is away from metal the signal is high, then close to metal (the extension) the signal is low. With the top open and the extension used as shown, the scan tool will display closed. The left side windshield latch also has a hall-effect sensor. The position of the latch is sent to the CVM, open or closed.

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Page last updated: Thu 6/29/2017 03:18:31 AM