Q: How Do the Gaskets in the Engine Protect It and Keep It Working?

Gaskets in an engine are used to seal one part to another due to variations from the machining or casting process. When a part is made, the surface will not be perfectly flat. There are small machining lines and surface imperfections that if two parts were put together, they would not be able to stopleakage of fluids。也可能有两种不同的材料或厚度，会导致两个部分以不同的速度扩展和收缩。如果不使用密封件或垫圈，这两个部分将无法密封。

汽车发动机中使用了许多不同的垫圈。发动机块和气缸盖之间有垫圈。这些垫片可能具有金属和不同垫圈材料层，以密封气缸的压缩。相同的垫片用于密封油和冷却液通道泄漏。垫片材料将在两部分之间占据任何缺陷，以及零件的​​任何膨胀或收缩，因为它们变热又冷却。您可能将塑料部件密封到金属零件或铝制零件上。

垫片材料将针对应用。有纸，塑料，金属，橡胶或氯丁橡胶和硅胶类型。也有这些材料组合制成的垫圈。不同的材料用于承受流体或燃烧的压力。例如，您可能会在气缸盖上看到金属或纸垫圈。橡胶或硅胶垫通常在阀盖上使用oil pans。

A gasket is only good as a one time use in most cases, except now some oil pan or阀盖垫圈are reusable and made from metal or plastic with different types of rubber or neoprene bonded to the metal or plastic. These type of gaskets use special shoulder bolts that cannot be overtightened in case they crush the gasket. Silicone can be used in place of a gasket and is called “Form-A-Gasket” by the manufacturer. The silicone is used in low pressure applications and works well when hardened to seal out coolant or oils. Water pump, oil pans, and thermostats use silicone on some applications.

垫片设计为在正常操作中密封两个零件，并将在温度，压力或流体中具有承受能力的耐受性。当这些东西在垫圈的指定操作范围之下或之上，它们可能会失败。当垫圈是新的时，它可能能够承受这些限制的某些操作，但是较旧的垫圈可能无法做到。当垫圈失败时，两部分之间可能会发生扭曲，并更换垫圈可能不足以再次密封两个部分。例如，如果由于发动机过热而开始垫圈开始泄漏]（//m.whoreclub.com/services/car-is-overheating-inspection），热量可能会将气缸盖的表面弯曲到新垫片无法再次密封的程度，除非头部表面再次加工。