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Brake Bleeding Process


[Music] In this segment, what we’re going to talk about today, is the importance of bleeding a brake system. The reason for bleeding a brake system is to remove any trapped air within the system. When you have trapped air within the brake system, you have compressibility. Compressibility leads into spongy brake pedals and brake fade. Most importantly, when you are bleeding a brake system, you want to have the right sequence. It is very important to reference your sequence manual on how to do it. Years ago, before the introduction of ABS and traction control, you always started from the furthest wheel back [from the master cylinder] and worked forward. Let’s take a look at what we are going to do here on this vehicle. Ok, we’ve decided what the sequence is on this vehicle by going through a sequence manual.. …and the sequence on this particular vehicle, you start at the right rear. There’s a couple different methods as far as bleeding a brake system. One method is a manual system that requires two people, an assistant up in the vehicle pumping the brake pedal… …while the technician opens the bleeders and cycles the bleeder screws to get the air out of the system. Another alternative is the pressure bleeder. Pressure bleeding is where you actually pressurize the brake system starting at the master cylinder, and push the fluid back through the system to bleed the wheel. The third system would be a vacuum bleeder. A vacuum bleeder actually hooks up to the bleeder screw… …and you pull the brake fluid back through the brake system to alleviate the air. We’re going to do the vacuum bleed on this vehicle. Ok, on this procedure, as we mentioned, we are going to do a vacuum bleed. The advantage of a vacuum bleed is you need one person to do it. The vacuum bleed, you are actually pulling air from the master cylinder through the system throughout the caliper. What we do is open up the bleeder, apply vacuum, and what you are going to see is the air bubble coming through the plastic tubes. Once those air bubble disperse all the way, you know you have the system bled. [Vacuum sound] As you can see, by applying the vacuum, we were pulling that brake fluid through the caliper into the reservoir. If you have trouble getting all the air out of the system, if the vehicle is equipped with ABS or traction control, you may need to use a scan tool to cycle the hydraulic control unit. On this vehicle, we really didn’t have any problem with it. We’ve got the right rear bled, let’s move onto the left rear at this point. During the bleeding process, one thing you want to make sure of is never let the master cylinder go empty. Always make sure it’s topped off. Most importantly, when you’re finished bleeding the brake system, top off that master cylinder at a proper level. At this point, what we do is we’ll evaluate the brake pedal. How’s that brake pedal? Assistant: “Feel’s Great!” Ok, we’ve got a nice high, hard brake pedal. Our next step will be to put the wheels on and road-test the vehicle, and I think we’re going to have a happy customer. [Music]

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