How To Gravity Bleed Your Brake System
Easy low cost one man method
Many vintage cars can benefit from a “Gravity Bleed” brake fluid bleeding method. It’s easy, generally takes less than 30 minutes and can be accomplished without an assistant for about $10-15 in equipment.
What You’ll Need:
· 1 Quart of your favorite brake fluid
· 4-5 feet of plastic tubing sized to fit snugly over the nipple on the brake caliper (generally 3/16” internal diameter tubing)
· An empty quart jar to hold residual fluid
· A small pair of vise grips and
· The proper open-end wrench for your bleed valve (common are M7, M9 and M10).
Jack the car up, support it “evenly” on jack stands, and pull the wheels so you access the calipers. You’re going to want to start with the longest line from the master cylinder first (usually the sequence is; passengers rear, drivers rear, passengers front, then drivers front).
Loosen the cover on your brake fluid reservoir.
Loosen all of your bleeders first with a very firm attachment of the ViseGrip pliers. Then, tighten them again so they are not weeping. The Vise Grips are especially important on the smaller M7 bleeders commonly found on early calipers because these smaller bleeders tend to get stuck and strip (yes, even with a 6 sided box-end or flare wrench). The later calipers have larger bleeders and stripping the hex is not so common.
At the first wheel, fix the plastic tubing to the bleeder then extend it up to a level that is “higher” than your brake fluid reservoir. It should hang down (from your c-pillar, or garage door frame or a supported stick) to the caliper. We like to tape ours to our c-pillar or roof of the car. Slide the plastic tubing over the nipple. Now slide the open-end wrench over the nipple and open the nipple with the wrench.
You should now begin to see the fluid rise in the tubing. It will continue on this path until it reaches the height of the brake fluid reservoir in the car. This usually takes 3-4 minutes. At this point, we like to tap the caliper a few times with a rubber mallet or the wood handle of a standard hammer. You can usually see small bubbles rise up through the tubing, especially at the start. Check your brake fluid reservoir to make sure it is properly topped off. After all of the bubbles have ceased, tighten the bleeder, pull the tubing off the bleeder while holding the jar to catch the fluid. Continue on to the next wheel.
Do all four wheels this way, keeping an eye on your fluid reservoir and replenishing the fluid as is goes down.
If you have a car with a pressure regulator or a bias control valve, you'll want to tap this valve during this first step and then drive the car once a pedal has been established. If you have new calipers and/or new pads, we now recommend that you bed your pads and in turn, the heat from this process will help break in the new seals in your caliper. If you are breaking in new caliper seals, your pedal will begin to come up with subsequent pad bedding procedures. Otherwise, with a stock system that just needed bleeding, you should be done.
For pressure regulator and/or bias control valve cars, we recommend you re-do the “Gravity Bleed” method once you've driven the car rather aggressively and bedded in your pads and seals.
See our “Pad Bedding Procedure” here: http://www.pmbperformance.com/bedin.html
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