How to Bleed the Brake System

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Here is a post from Larry on how he bleeds the brake system:

One thing I don't think I've ever shown is the process I use to bleed brake systems. Below is a bleeder bottle I made up by soldering two sets of brass tubes in. Two short and two long. The long ones are connected to the bleeder on the caliper/s if there's two. This allows you to see when all the air is pumped out while you bleed the system. This isn't a new thing though. It's an old idea that's been around for years. It saves on making a mess too.

Here's my twist on bleeding the air out of the hose and caliper. A year or so ago I came up with a clean way to bleed air out. I used an extra banjo bolt with a 10X1.25 nut and two brake hose washers. I drilled out the end so that the tip of a large 60cc syringe fit tightly in the hole. When the assembly is tightened up it seals the end of the hose like it was bolted to the master cylinder. With the syringe filled with new Dot3 fluid and the bleeder opened up and connected to the bottle, I slowly force the fluid into the hose so it forces the air out all at one time. Going slow works much better than forcing it in fast. If you force it, air bubbles will get formed and stuck inside the hose and around the caliper piston.

I leave this sit just like this while I bleed the master cylinder. This way no air creeps in.

When that is bleed out I bleed the master cylinder. Filling the reservoir for the first time after rebuilding it will never start pumping fluid by just pulling the lever in and out. The process goes like this. Pull the lever in and hold it there. Now press your finger over the exit of the master cylinder where the brake hose is connected to seal it off. Now let the lever out. Slightly let up a little pressure on your finger and pull the lever in again. Hold it and press finger hard against the end again. Repeat this process until you start getting fluid pumping out. You'll see air bubbles coming into the res. through the two hole inside while you do this. It's allowing fluid to fill around the piston.

I put a plug in the end of the master after I get all the air pumped out. BTW, be sure to put a good sized rag under the master while you bleed it or you'll have fluids all over everything. And pump slowly so it's a controllable pressure that doesn't squirt past your finger tip. Brake fluid in your eyes is VERY uncomfortable.

Now remove the banjo bleeder bolt from the hose and connect hose to the master. While your screwing in the bolt, SLOWLY be pulling in on the lever. It will keep air from entering the piston area again. When it's all together, pull in on the lever and slightly loosen the banjo bolt so the air gets forced out, and tighten up the bolt after each pull in on the lever. Don't let up on the lever until the bolt is tightened up. Do this until you see no more air bubbles.

Now that it's all done, pull in on the brake lever and tie in down. Leave it this way overnight with the bars turned to the left so the master cylinder is at it's highest point. This will allow the tiny left over air bubbles to travel up the hose and out of the master cylinder. I know it sounds strange, but it works trust me. If you thought the brakes felt good when you were done, you'll really like it when you untie the lever the next morning. BTW, I use a strap of Velcro. When I used wire or a zip tie it took several days for the impression to work it's way out of the rubber or foam grip.

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