Wednesday, February 4, 2009

BMW? kerosakan enjin2 mereka

  1. An "oil spray bar" is mounted above the camshaft. This hollow metal tube sprays oil over the camshaft and rocker arms, but with time the two banjo bolts that hold the bar in place may loosen themselves. As a result, oil passage through the spray bar will get restricted, and the camshaft and rocker arms will not get cooled and lubricated properly, possibly leading to fatal wear.
  2. On some models, the return valve in the oil filter housing fails with time, thus making oil run out after stopping the engine, instead of keeping it in the housing. While not a critical problem, it results in the engine needing up to five seconds to build up proper oil pressure upon engine start. BMW replaced the oil filter housing with a more durable valve around 1991.
  3. While not a problem by design, the spacing between the valve rocker arms and the valves must be adjusted approximately every 30,000 km (20,000 miles). Failure to adjust might lead to poor running, increased fuel consumption, and engine wear.
  4. The engine fan is mounted with a viscous coupling that expands when heated. As the engine becomes warm, the coupling gets a better grip on the fan, thus leading to increased rotation of the fan, and more airflow. If this viscous coupling fails, the fan will only rotate relatively slowly (as driven by the engine by a V-belt), and will not provide sufficient cooling, leading to overheating. Overheating can extremely quickly lead to engine failure, such as a destroyed headgasket or a warped or partly melted cylinder head.

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