（6）Maintain correct viscosity (free flowing at all temperatures).
保持正确的粘度（在所有温度下自由流动）。
When the brake fluid boils, it becomes vapor. A vapor can be compressed, but a liquid cannot be compressed. Pressing on the brake pedal will compress the vapor in the lines instead of transferring the pressure through the fluid. This can lead to partial or complete braking system failure, sometimes called brake pedal fade. Mountain driving puts increased duty on brakes and brake fluid. The boiling point drops at high altitude. This naturally increases the tendency towards vapor lock. In fact, vapor lock in the hydraulic braking system is the primary reason for brake pedal fade.
当制动液沸腾时，它变成蒸汽。
可以压缩蒸汽，但不能压缩液体。
按压制动踏板将压缩管线中的蒸汽，而不是将压力传递通过流体。
这可能导致部分或完全制动系统故障，有时称为制动踏板褪色。
山地驾驶增加了刹车和制动液的使用。
沸点在高海拔下降。
这自然增加了气体锁定的趋势。
事实上，液压制动系统中的汽油锁是制动踏板褪色的主要原因。
Vehicle manufacturers recommend brake fluid that meets or exceeds SAE (Societyof Automotive Engineers)andDOT (Department of Transportation) specifications.
车辆制造商推荐符合或超过SAE（汽车工程师协会）和DOT（运输部）规格的制动液。
Standard brake fluid (DOT 3) is composed chiefly of equal parts of alcohol and castor oil. This combination of fluids works well under normal conditions but it easily boils and becomes a vapor under heavy-duty applications. It also tends to separate when exposed to low temperatures.
标准制动液（DOT 3）主要由酒精和蓖麻油组成。
这种流体组合在正常条件下工作良好，但在重载应用下容易沸腾并成为蒸气。
暴露于低温时也容易分离。
The increasing requirements of brake fluid led to the development of silicone brake fluid,such as DOT 5. This fluid achieved low water pickup and good corrosion protection and also provides good lubrication qualities and rubber compatibility.
制动液的要求越来越高，导致了DOT 5等硅胶制动液的开发。
该液体实现了低吸水率和良好的防腐蚀性能，并且还具有良好的润滑性能和橡胶相容性。
5.Brake valves
5.闸阀
There are typically five types of valves in vehicle braking system to adjust the braking force distribution.
车辆制动系统中通常有五种类型的阀门来调节制动力分布。
(1)Metering valve
（1）计量阀
Most vehicles that have front disc and rear drum brakes are equipped with metering valve. This metering valve controls, or delays the flow of brake fluid to the front brakes. The rear drum brakes take longer to respond than the front disc brakes. The valve ensures that front disc brake do not act before the rear drum brake. The delays is long enough to allow the rear drum brakes time to react. This delay is particularly necessary during light braking and on slick road surfaces.
大多数具有前盘和后鼓式制动器的车辆配备有计量阀。
该计量阀控制或延迟制动液流向前制动器。
后鼓式制动器比前盘式制动器响应时间更长。
阀门确保前盘式制动器在后鼓式制动器之前不起作用。
延迟时间足以使后鼓制动时间做出反应。
在轻刹车和光滑的路面上，这种延迟特别有必要。