The制动主缸is an integral part of modern car braking systems. Inside the master cylinder is a seal that holds the pressure from the brake pedal and transfers more fluid into the lines, which then applies the brakes.当这个印章开始失败时，您的刹车踏板将无法承受压力，并在尝试施加刹车时会沉入地板上。

Replacing yourmaster cylinderdoesn’t require too many tools, mostly just care and attention to detail. In particular, your biggest concern will be fluid dripping and being able to quickly clean it up so you don’t forget. Bleeding the master cylinder on the car is possible, albeit slightly more time consuming, so bench bleeding is recommended to help get the process started.

The following instructions will go over how you can replace the brake master cylinder yourself.

第3部分，共3部分：准备旧的主缸以拆除

需要的材料

• Brake fluid
• Brake master cylinder
• Gloves
• Line wrench
• Rags
• Ratchet
• Safety glasses
• Socket
• Turkey baster

• Vice

• Tip：对于金属制动线，您需要在首次打开破裂时使用线扳手，否则很有可能会损坏配件。这些线通常约为10毫米，但是请确保在尝试打开它们之前确认大小。将主缸固定的螺母较大，并根据车辆的不同而变化。

• Note: It is possible to bleed the master cylinder without a vice by propping it against a wall or having someone hold it. The vice is convenient because it can hold the master cylinder perfectly still while you are pumping the air out.

步骤1：从主缸中清除尽可能多的流体。Use a turkey baster to siphon the brake fluid out of the reservoir.

Although this is not a completely necessary step, this can greatly help to reduce any mess later on.

步骤2：删除任何可能在路上的组件。拆卸管道和连接等连接，例如制动助力真空软管，可以帮助您更轻松地访问主缸的侧面。

Step 3: Unplug the fluid level sensor。在塑料储层上定位流体水平传感器，而不是主缸本身，然后拔下插头。

Step 4: Crack open the brake lines with the line wrench。随着主缸仍然固定在制动助力器上，裂缝打开线条并将其轻轻拧紧，以免流体泄漏。

何时准备完全卸下主缸时，这将使以后更容易。

步骤5：卸下固定主缸的螺母。Loosen and remove each nut securing the master cylinder to the brake booster.

It is common for there to be a washer for each nut so make sure not to lose any pieces.

Part 2 of 3: Bench bleeding the new master cylinder

At this point, you’re almost ready to pull out the old master cylinder. But first, you will need to get the new master cylinder prepped a little by bleeding it on a bench to remove most of the air from inside.

Step 1: Secure the new master cylinder。Using a vice, clamp the new master cylinder in place.

Put some rags on the ground beneath the cylinder as there will be some spillage.

另外，请确保您戴着手套和眼睛保护，因为制动液与人体的混合不佳。

Step 2: Fill the master cylinder with brake fluid。尽可能填充主缸。在整个过程中，将在主缸内泵送液体，其中一些将从制动线端口中出来。

You need to keep the master cylinder filled with fluid, otherwise air will get inside and you’ll have to start over, so make sure the level is always topped off before each pump.

• Note: If your new master cylinder comes with a reservoir, go ahead and install it at this point. This will make it easier to keep the master cylinder from running dry.

步骤3：推入活塞。Use your hand to manually push in the piston. This will start filling the inside of the master cylinder with fluid and the level will go down. Don’t release the piston immediately.

步骤4：完全覆盖制动线端口。While still pushing in the piston, use your fingers to cover all of the brake line air ports.

When you later let the piston out, it will suck air through the ports if they are not covered. You are trying to let all of the air out of the master cylinder, not let more come in.

步骤5：放出活塞。当您的手指仍在覆盖端口时，释放活塞。您会看到一些气泡，流体水平可能会下降一些。

步骤6：顶部流体水平。在仍覆盖制动线空气端口的同时，向主缸加入更多的流体，以免干燥。绝不应允许气缸干燥。

步骤7：推入活塞。类似于步骤3，再次手动推入活塞。流体可能会从其中一个端口开始出来，因此用手指轻轻覆盖它们，以便流体不会在各处喷洒。

You want the fluid to come out so don’t completely seal up the ports.

Step 8: Cover the ports and release the piston。再次密封端口并释放活塞。

Step 9: Keep pumping until fluid is coming out of all of the ports。重复步骤3至8，直到流体从所有端口出来。然后，新的主缸准备安装。

Remember to check the fluid level and fill it as needed every time you release the piston. If you don’t have a reservoir, you’ll want to add fluid before every pump.

Make sure your fingers are covering the ports every time you release the piston otherwise air will get inside.

第3部分的第3部分：安装新的主缸

You’re now ready to finish removing the old master cylinder and install the new one.

步骤1：完全拧下刹车线。使用扳手，完全拧开每条制动线。制动液会开始泄漏，因此请确保准备好一些破布以将其吸收。

Since you’ve already cracked them open, a regular wrench should be okay, just take care not to round off the nuts.

• 警告: Brake fluid can damage rubber and paint so make sure any fluid that is spilled is cleaned up quickly.

Step 2: Remove the master cylinder。With everything disconnected, you can now remove the master cylinder.

确保卸下主缸和制动助力器之间的橡胶密封。

新的主缸应该有一个新的密封件，并且两者都可以在制动系统中造成问题。

• 警告：当您取出旧的主缸时，请注意任何制动液滴。同样，请确保准备好抹布来清理所有滴水，尤其是在油漆上。

步骤3：将储层转移到新的主缸。If you’re new master cylinder does not come with its own reservoir, you will want to remove the reservoir from the old master cylinder and transfer it to the new one.

通常，储层将有一个将其固定在主缸上的夹具。请确保将其拧紧在新的上，以免流体泄漏。

步骤4：开始安装新的主缸。Once the reservoir is in place, you can start to install the new master cylinder onto the vehicle.

Make sure the rod coming out of the brake booster fits into the piston on the master cylinder. This rod is what pushes the seal inside the master cylinder to pump fluid into the lines.

Step 5: Start screwing in the brake lines。Before you completely tighten down the master cylinder, get the brake lines started by hand.

This way you have a little wiggle room to get everything lined up perfectly.

• 警告：开始拧紧这些线时要小心。如果交叉线程线，则需要再次替换主缸。

步骤6：拧紧安装螺母。接下来，拧紧安装螺母，确保使用以前在那里的任何垫圈。用一只手将它们拧入，这样您就不会超越它们。

Step 7: Tighten brake the line connections。使用主缸螺栓固定，您现在可以完全拧紧制动线连接。

Use the line wrench again and only one hand so you don’t overtighten them.

Step 8: Reconnect any hoses or wires。将流体液位传感器重新插入，如果您之前卸下制动器，则将真空软管重新连接到制动器助推器。

Get everything back to how it was before you started the job.

步骤9：流血系统。Since all the lines were disconnected, you’ll need to bleed each one at the caliper.

While you are流血, keep an eye on the brake lines coming out of the master cylinder for leaks.

• Tip: Have a friend help you pump the brakes while you open and close the bleeder valves.

Step 10: Take the vehicle for a test drive。If the brake pedal is nice and hard after bleeding the system of air, it is time for a road test.

Start with an empty street or parking lot at a low speed. Check the brake line ports for leaks after stepping on the brakes a few times. If everything seems okay, you can start going on normal roads.

Maintenance of your braking system is perhaps the most important way to keep you safe while driving. Regular brake maintenance such as流血will also help keep your master cylinder and other brake components in working order for the long haul. If you are experiencing any issues with this job, a certified technician at YourMechanic can assist you inreplacing your master cylinder。如果您还有其他制动问题，您的Mechanic也提供万博体育入口full brake system inspectionsso that you can always make sure that your brakes are in great shape.