BMW 3 vehicles have "universal body" diagram where a floor panel with front and rear side beams is used (spars) frames, which play the role of carriers for the rest of the car body parts, front and rear suspensions and other mechanical components. Some of the components are particularly vulnerable to accidents and can be screwed off and repaired or replaced. These include the hood, trunk lid, doors and front fenders. Front and rear windows glued.
This Chapter includes descriptions only of procedures for general care of the car body and restoration and repair of body panels that lie within the skill of the average amateur mechanic.
Many of the above structural elements are fixed with so-called Torx screws, which require a special screwdriver to unscrew.
If any work is carried out on the internal equipment, the following instructions must be observed:
If any electrical work is also carried out while working on the internal equipment, be sure to disconnect the negative cable (-) battery. To do this, read the instructions in Section Removing and installing the battery. Disconnection or disconnection of any electrical wire should also be considered as work on electrical equipment.
- It is recommended to use a plastic wedge, eg HAZET 196555-20, to remove the plastic cladding and visors.
- Clamps damaged when removing the lining must be replaced.
- Seats, belts and airbags are important safety features. Only the work described in the chapter should be carried out. Other work is recommended to be carried out at the service station.
Body work safety precautions
It is not allowed to weld or solder with soft or hard solders the elements of the air conditioning system filled with the working fluid, or if there is a danger of their heating.
Do not open the cooling circuit of the air conditioner, as contact with the skin may cause frostbite.
In case of accidental contact of liquid with the skin, immediately rinse the affected area with cold water for at least 15 minutes. The air conditioner fluid is colorless and odorless and heavier than air. If coolant leaks, there is a risk of poisoning in the underside of the vehicle (the presence of liquid is not felt).
The protective coating of the PVC bottom in the place of welding must be cleaned with a wire brush and, heated with hot air to a temperature of +180°C, removed with a spatula.
When the PVC coating is heated above +180°C, hydrochloric acid is formed, which has a strong corrosive effect. In addition, vapors are formed that are harmful to human health.
Body elements subjected to increased corrosion are galvanized. Do not sand the zinc coating before welding (it is allowed to remove the coating only when soldering with hard solders). In this case, the welding current should be increased by 10%.
When welding galvanized sheets, zinc oxides are formed. Safety measures require good ventilation of the welding area.
When repairing the paintwork, it is allowed to heat the car in a special oven to a temperature not exceeding +80°C. Otherwise, there is a risk of damage to electronic devices.
When carrying out welding work on a vehicle with installed controls, the following must be observed:
Disconnect the negative cable (-) battery with the ignition off. The battery is located in the luggage compartment behind the cover on the right side. For BMW 316i, 318i, the battery is located in the engine compartment.
Disconnecting the battery clears the fault memory of some controls. If necessary, read the fault memory before disconnecting the battery. Refer to Section Troubleshooting. It is desirable to carry out work in the conditions of a service station.
Isolate the negative pole (-) battery to prevent accidental contact.
If welding or other work involving the formation of sparks is carried out near the battery, it is imperative to remove the battery.
When carrying out welding work, the terminal of the welding machine must be placed as close as possible to the welding point and must be well connected to the body, the maximum distance is 1 m.
It is not allowed to use the ground connection of a vehicle with fixed wires as a ground connection for a welding machine. If necessary, first disconnect the wires and protect the thread of the earth bolt with a nut.
For vehicles with a navigation system, the navigation magnetic field probe must be recalibrated after welding has been completed (service station work).
Galvanized sheets are installed on the structural elements of the car, which are particularly exposed to corrosion. Do not remove the zinc layer before welding. It is only removed before brazing. In this case, the current strength must be increased by 10%.
The operation of lifting and placing the vehicle on stands is dangerous! Therefore, before carrying out the operation, read Section Jacking and towing
Body clearances
When installing body elements, the specified clearances must be observed. Otherwise, for example, there is a rattle when closing the door or increased wind noise while driving. The gap must have a constant width along the contour of the fit of the parts. The deviation must not exceed 1 mm.
The following condition must be met. The surfaces of adjacent elements must be parallel. An inward displacement of 1 mm is allowed for elements located closer to the rear of the vehicle in relation to elements located in front of the body.
For example: The front edge of the rear door may be 1 mm deeper than the rear edge of the front door.
The required gap values are shown in the table.
Designation of body pillars front to back A, B, C
cross section | A-A | B-B | C-C | D-D | E-E | F-F | G-G | H-H | I-I | K-K |
a = | 4.25 ± 0.75 | 12.8 ± 0.2 | 13.9 ± 0.2 | 15.7 ± 2.0 | 17.2 | 4.0 ± 0.75 | 15.0 ± 2.0 | 8.8 + 3.0/-0 | 0.0 ± 1.0 | 1.0 ± 1.0 |
b = | 0 ± 1.0 | 4.5 ± 1.0 | 4.0 | 4.0 | 0 ± 1.0 | 0.0 ± 1.0 | 1.0 + 1.0 | 1.0 - 1.0 | 1.0 ± 1.0 | |
c = | 25.0 ± 1.0 | 15.0 ± 2.0 | 4.5 ± 0.75 | 5.0 +1.5/-1.0 | ||||||
d = | 15.0 ± 2.0 | 15.0 ± 2.0 | ||||||||
1= | Side frame | channel cladding | ||||||||
2= | Front door | Channel | ||||||||
3= | Windshield | Front door |