How to Bleed Air Braking System

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In this video we're going to show you how to bleed disc brakes. The vehicle we're working on is a 1974 Pontiac. This procedure is generally the same for any vehicle that has disc brakes. The tools you'll need: You will need a wrench that's the appropriate size for your bleeder valves. On this vehicle it's a 3/8 inch but it could range from an 8mm to a 13mm or a ¼ inch to a 3/8 inch. Then you'll also need something to catch the brake fluid, and you'll see we put together a little bottle with a hose to do that.

You'll start out by removing the cap for your master cylinder and making sure that your master cylinder is topped off. You'll want to do this periodically if you're bleeding all your brakes. You'll want to periodically check your master cylinder and make sure you don't run too much fluid out of it. Before you bleed, put your cap back on and secure it with the clamp. You're going to look for this fitting here and that's your brake bleeder fitting. This is a 3/8 inch on this car but it can be anywhere from probably ¼ inch to 3/8. Make sure it's free. There are two ways you can do this. If you have a helper, which I do have a helper in my car right now, what you can do is you can just use a rag or something to catch the fluid but what I'll have him do is I'll tell him to press the brakes and then I'll release or loosen the fitting and that'll let air out.

"Press the brakes." You can see that the air comes out in the bottle here. "Let off." Okay. "Press the brakes." As I loosen see all the air come out? "Let off." The other way to do that is if you're alone and you don't have a helper, you can make a little bleeding kit like this. You put more fluid in here and you hook it up and just put the bottle somewhere safe and secure. You can just open up the bleeder valve and pump the brakes and it will force air out and then suck air in with the bottle. "Go ahead and pump the brakes." Air goes out. "Let off." Then fluid will go back in. "Pump the brakes. Let off. Keep going. Back off, just keep pumping them." Now you can actually see some of the bad old fluid coming out. "Let off. One more time. Let off." He's pumped the brakes enough times now. There's no more air coming out. We're going to tighten this up. "How does the brake feel?"

Pretty good."�

"Pump it a few more times. Alright now, one more time. We're just going to do it one more time." No more air at all so we're all set. Now we can take the hose off and we're all done.

Then you would repeat that. What you want to do is you want to do the furthest wheel first and then you go to the wheel that's closest to the master cylinder and once you've done that one, you come back to this one and just make sure that there's no air.

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