Brake system bleeding

From 2nd Generation Rx7 Service Wiki

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Revision as of 19:05, 29 March 2006

After replacing components such as calipers, brake lines, the master cylinder, etc. it will be necessary to remove the air that was introduced into the system during replacement. If the air isn't bleed out the brakes will be very soft and the chance of internal corrosion forming is much greater.

Contents 1 Optional Tools 2 Conventional Bleeding 2.1 Tools and Supplies 2.2 What to Bleed 2.3 Bleeding Process

Optional Tools

There are many tools available that can make the bleeding process easier:

• Speed bleeders
• Vacuum bleeding systems
• Bleeding kits with integrated check valves

Conventional Bleeding

If none of the optional tools are your style you can always bleed them the conventional method. You'll need the following tools:

Tools and Supplies

• Flare wrench (you will strip the bleeders using a standard wrench)
• 3-4 ft. piece of clear vinyl tubing that fits snugly on the bleeder
• Glass container filled with a few inches of fluid
• Fresh brake fluid

What to Bleed

Now that you have all the supplies together you need to figure out which components you wish to bleed. It is unnecessary to bleed the entire system when replacing a single component, just the section effected by the replacement. There is no harm in bleeding the entire system, but if you don't have to you can save a bit of time. If you decide that it's necessary to bleed the entire system, use the following chart to determine the proper bleeding order (eseentially the furthest point from the master cylinder gets bleed first then goes in order by distance.)

If you're bleeding a rear caliper that has been replaced or rebuilt you must use the lower of the two bleeder screws before bleeding from the upper screw. This will ensure that no air is trapped in the lower passages of the unit.

Bleeding Process

Now that you know where to focus, here's the process:

1. Place the unit of jackstands and remove the wheel(s)
2. Top off the fluid resevoir
3. Put the wrench over the bleeder, then attach the vinyl tube to the bleeder screw, then place the other end into the container of brake fluid. Make sure that the tube is completely immersed in the fluid so you don't have to worry about air being sucked back into the system.
4. Loosen the bleeder just enough for the fluid to be pumped out.
5. Pump the brake pedal until no more air bubbles are coming out of the unit. Keep an eye on the fluid level at the master cylinder and fill it as you go along. You must avoid letting the level get below the minimum mark or you'll be sucking air back into the system.
6. Tighten the bleeder so it's snug, then remove the tube and wrench. Do not overtighten or you will damage the caliper and bleeder.
7. Repeat the process for the rest of the system that requires bleeding, then top off the resevoir one more time.

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