Body and underbody maintenance (BMW 3 Series E46)

1. The general condition of the vehicle body is one of the parameters that determines its value. Body maintenance is not difficult, but it must be regular. Neglecting this rule, especially after minor damage, can quickly lead to further deterioration of the body and expensive repairs. It is important to remember this and pay attention to those parts of the car that are difficult to inspect, such as underneath, inside the wheel arches and in the lower part of the engine compartment.

2. The main type of body maintenance is to wash it regularly with plenty of water (from a hose). This helps to remove any solid particles that may have stuck to the car. It is important to remove all these particles during the washing process to prevent future scratches. It is essential to wash the wheel arches and subframe to remove all the dirt that retains moisture and accelerates the rusting process. It may seem strange, but the best time to clean the subframe and wheel arches is wet weather, when the dirt remains damp and soft. In very wet weather, the subframe usually automatically clears itself of large build-ups of dirt and this is the best time to inspect it.

3. Except for vehicles with a wax-based underbody coating, it is recommended that the subframe and engine bay be steam cleaned periodically to allow a thorough inspection to determine if minor repairs or replacements are needed. Steam cleaning is available in many workshops and is essential for removing oily dirt. If steam cleaning is not available, cleaning with oil solvents applied with a brush may be used. This may simply dissolve the dirt. Please note that these methods should not be used on vehicles with a wax-based underbody coating, as this will remove the coating. Such vehicles should be inspected annually, preferably before winter, with the underbody washed and any damaged areas of the coating repaired. The best option is to replace the coating entirely. It is also advisable to use injection wax protection on door panels, window sills, etc., as this provides additional protection against rust in areas not provided by the manufacturer.

4. After washing the paintwork, wipe it dry with a chamois to ensure that the finish is smooth. Applying a coat of polish will provide additional protection for the paintwork from harmful atmospheric impurities. If the paintwork has lost its shine, use a mixture of cleaner and polish. It requires some effort to apply, but the loss of shine is usually the result of infrequent washing. Particular care should be taken when caring for metallic paintwork: non-abrasive cleaners and polishes should be used for the finish of such a coating. Always ensure that the holes and tubes provided for drainage and ventilation are completely open and that water can flow freely through them. A dirty film may occasionally appear on the windshield and windows, which should be washed off with a suitable glass cleaner. Never use wax or polishing pastes for the body or chrome parts to clean the glass.

(Information taken from this resource «BMWMAN.ru»)