How to Bench Bleed a Master Cylinder

Video Transcript

"DOUG JENKINS: Hi, I'm Doug. I work with 20 great guys in St. Louis at Doug Jenkins Custom Hot Rods, and we're going to do some work for you today on Expert Village. The next activity is to get the master cylinder ready to install. The first step there is bench bleeding the master cylinder. A brake master cylinder forces fluid from the master cylinder which is under your brake pedal foot to the hydraulic cylinders at each wheel. The miracle of hydraulics depends on no air. Air compresses, fluid doesn't, so you need to get all of the air out of the system before you can have good effective brakes. So Mark is going to bench bleed the master cylinder. There's a couple of tricks to getting the air out of the master cylinder that you can only do on the bench. If you just install a dry master cylinder in the car, you may not ever be able to get all the air out of it. So there's kind of a careful procedure, Mark is going to go through here to bench bleed it. He starts with clean, new, brake fluid, and this kit actually provided brake fluid with it. How to set up now is you just plug off the fluid holes and push the plunger in, in and out, a small amount until you see all the air stop coming out. And if you watch there in the fluid, you can see the bubbles coming out when he's done. So you just do this a bunch of times until no more bubbles come out. But don't be impatient about it. If you still have bubbles, don't install it. You'll never get the bubbles out."