source: http://www.carsdirect.com/car-maintenance/4-most-common-causes-of-an-auto-vacuum-leak
按照此文的觀點，最大可能性是裝配不良，屬先天不足；其次為管線老化磨損；第三是結頭破裂失效；第四是密封材料方麵的問題，正如你的具體情況。僅供參考：
4 Most Common Causes of an Auto Vacuum Leak
An auto vacuum leak is one of the more common causes of runability issues with modern cars. Fuel injection systems rely heavily on engine vacuum in order to gather information about the current conditions that the motor is operation under and calculate the correct fuel mixture to optimize both power and fuel economy. If a vacuum leak is present, then the engine computer isn’t able to obtain the information it needs and it is forced to run the motor under a “fuel rich” condition in order to protect it against running lean and possibly causing damage to the motor due to predetonation. Here are some of the most common causes of an auto vacuum leak and their corresponding fixes.
- Loose or Improperly Installed Vacuum Fittings – Most commonly, A vacuum leak develops due to a connection that is simply loose or not installed correctly. If you believe that your car’s motor has a vacuum leak, first check all the connections on the vacuum lines in order to make sure that there isn’t a simple loose fitting that is causing the problem. Move from connection to connection in sequence, examining and handling each connection to ensure that they are installed correctly.
- Failed or Ruptured Vacuum Line – A failed vacuum line is probably the second most common cause of an auto vacuum leak. Oftentimes vacuum lines fail and begin to leak after they become brittle or weak with age and crack. Other times a vacuum line will become abraded due to engine vibration wearing it down over time and then rupture. To repair a failed vacuum line, simply the length of line that has developed a leak with a new vacuum hose.
- Broken or Failed Connectors – Much like the vacuum lines themselves, the plastic connectors used to join the lines degrade with age and become more prone to cracking. A bad connector will often shear directly along the point where the vacuum line attaches to it. Repairing a failed connector is fairly simple. Replace it with a matching type of connector and trim the hoses that lead to it to fit. You may consider replacing plastic connectors with more durable metal type connectors to avoid this problem in the future, especially on lines that are in areas that are consistently exposed to heat.
- Failed Intake Manifold or Plenum Gasket – Another less common cause of auto vacuum leaks is a bad gasket at the intake manifold or plenum. The gasket forms a seal between the hard parts of the intake to prevent outside air from entering the system. If a gasket fails it generally causes immediate and pretty severe issues with runability. A failed intake manifold or plenum gasket must be replaced with a new gasket in order to achieve the proper seal. Locate the correct gasket kit and remove the old gasket. It’s a good idea to pay attention to the location of the gasket breach so that you can make sure to use extra care on that area to ensure it doesn’t fail again, including using proper torque on the manifold bolts.
