BMW X3 Service & Repair Manual: Spot-weld bonding steel components

IMPORTANT: Comply with the following topics from "Body, General": Safety regulations .

Handling electrical system, electronics, airbags and restraint systems .

• Beginning with E65 the spot-weld bonding process is used to increase vehicle rigidity. In partial body areas, a 1-component adhesive is applied to the spot flanges and this is followed by resistance pressure spot welding. The adhesive is hardened only after the paint drying process (at approx. 180 ºC).
• In the case of repairs, adhesive is not applied to the spot flanges. The number of welding spots is doubled as a substitute for the omitted adhesive.
• Minimum distance between welding spots (1) is 25 mm. Important! The minimum distance must not be undershot! If there is not enough space for twice the number of resistance weld points, each non-made resistance weld point must be replaced by a MAG weld seam (2). Length of a MAG weld seam = 20 mm.

  Set the MAG weld seams at equal intervals distributed on the face.

• The following procedures are used as a substitute for spot-weld bonding:
  • MAG welding (M etal A ctive G as welding)
  • Resistance pressure spot welding (referred to in the following and in the repair instructions as spot welding).
• Adhesive is not applied between the spot flanges on new parts in the case of 2- or multi-sheet joints.

  Areas which cannot be reached by the spot-welding tongs can be joined by MAG plug welding. The number of welding spots is doubled as a substitute for the omitted adhesive.

• Exceptions (e.g. E65) are described in the relevant repair instructions. Apply welding spots to existing welding spots on new part. This is necessary because the adhesive between the spot flanges of the new part acts as an insulator.

CAUTION: Extract smoke and fumes during welding work.