Notes on Rear Window Cementing (Hard Top)

54 21... Notes On Rear Window Cementing (Hard Top)

General:
The rear window is bonded to the hard top. Bonding increases the hard top's torsional rigidity. To obtain perfect bonding, comply with the installation procedure described in the following.
The car can be towed or driven without the rear window fitted.
- In winter, the hard top must stand in a room with a temperature of at least 15 °c.
- A second person is sometimes needed to remove and install the rear window/hard top.

On-the-job safety:
When working with adhesive products (adhesive, cleaning agent, glass primer etc.):
- Wear protective goggles, protective gloves and if necessary an apron.
- Ensure rooms are well ventilated.
- Change work clothing contaminated with adhesive immediately.
- Change work clothing contaminated with solvents and swelling agents immediately (keep spare work clothing on hand).
- Take skin protection measures, provide washing facilities including hot water, use silicone-free skin creams
- Provide eye bath facilities, change water regularly (once a month).
- Observe relevant safety regulations.
- Do not eat, drink or smoke in areas of PUR processing.

Adhesive:
The BMW-approved 1-component polyurethane adhesive must be used for bonding.
- SikaTack - Ultrafast* for warm processing

* Sourcing reference: BMW Parts Service

The adhesive is applied with a cartridge gun (pneumatically or electrical driven, sourcing reference: BMW Parts Service).

Use of SikaTack - Ultrafast (warm processing):
- Open aluminum membrane at rear end of cartridge
- Heat adhesive for one hour in cartridge oven (sourcing reference: BMW Parts Service) to 80 °c
- Remove hardened adhesive compound before further processing. Sealed adhesive:
- can be heated several times
- may only be stored for max. 10 hours at 80 °C heating
- adhesive will be damaged if this time is exceeded
- damaged adhesive must not be used and must be disposed of in compliance with national regulations

Adhesive expiry date:
The repair set and adhesive cartridges are marked with an expiry date.
The adhesive cannot be used after this date.

Adhesive disposal:
Pure hardened adhesive is handled as normal waste.
The adhesive is disposed of in paper bags so that it can react with moisture.
Non-hardened adhesive, cartridges and mixtures of adhesive and solvents and the like must be disposed of as special waste.

Removing rear window:
Cover side walls and if necessary interior equipment with protective covers.
When cutting rear window out:
- Wear protective goggles and cut-proof protective gloves.

Cut through adhesive bead of rear window with an electric cutter with an oscillating blade (sourcing reference: BMW Parts Service).
Prior to each use, regrind the blade with a grinding stone while the machine is running (new blades also).
Avoid paintwork damage to hard top cutout; a second person and special tool 00 9 341 are therefore required.
Carefully insert blade between hard top cutout and rear window.
Guide bridge of blade parallel to rear window.
Cut through adhesive bead as closely as possible to rear window all round.
To remove residual adhesive bead in hard top cutout:
- Use a scalpel for heavy-duty applications
- Remove adhesive residue down to a thickness of approx. 0.5 mm

Paintwork damage in hard top cutout:
Paintwork damage must be repaired without fail.
If there are only scratches in the non-visible bonding area, these are to be treated with Sika bonding agent 205/5, refer to "Treating bonding area in hard top cutout".
If a complete build-up of paint is necessary in the visible area:
- Tape off primed adhesive flange before applying top coat.

Caution: Observe hardening time of BMW MS-AK multibase filler, otherwise a perfect bond is not guaranteed.

Treating bonding area in hard top cutout:







Caution: Do not use Sika remover 208 for cleaning on adhesive area.

Preparation for assembly:
Prepare the plastic nozzle for shaping the adhesive bead; this can be cut to fit during the air drying times.
If necessary, lay a sample bead.
The cartridge must be positioned vertically with respect to the rear window.
To protect the adhesive bead, the inside edge of the window is coated with (black) UV-resistant glass ceramic material and must be treated as follows.

Treatment of glass ceramic surface (inside of window):







Assembly:

Important:
Assembly must follow within 10 minutes otherwise the adhesive bead will form a skin and will no longer be able to bond properly.
Dual-lock tapes are used to secure the rear window.
Window slippage results in leaks, wind noises and the risk of breakage.

Remove contamination by residual adhesive immediately with adhesive cleaner (Sika remover 208, sourcing reference: BMW Parts Service). Do not press out rear window glass again for this purpose.
Hardened adhesive can only be removed by machine.

Hardening:
The adhesive hardens through reaction with air moisture at room temperature.
Minimum hardening time is achieved at 22 °C and 38% relative air humidity.
Adhesive hardening process is interrupted absolutely at ambient temperatures below 5 °C. In this event, there will be no increase in the strength of the adhesive bond.
During the minimum hardening period, the hard top must not be subjected to one-sided load such as e.g.:
- Mounting hard top on kerb
- Do not set up hard top at an angle
- Do not set up hard top on hard top trolley
- etc.

If the hard top is mounted on the car:
Moving around inside the workshop on a flat surface is permitted but do not under any circumstances drive over approach ramps for example in multi-storey car parks.
If the minimum hardening times are not adhered to:
- The rear window will be displaced, resulting in leaks, wind noises and the risk of breakage

Adhesives and their minimum hardening times:







Locate leakage:
- by spraying with water underneath dust seal
- with an ultrasound leak detector (sourcing reference: BMW Parts Service)

Repair instructions for removing and installing rear windows (hard top).
Refer to MG 54.