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Make a Bench Bleeding Tool DIY Bleed Car Truck Master Cylinder

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Created on: 2020-06-09

Watch this video to learn how to make your own tool to bench bleed a new brake master cylinder!

Hey, friends. It's Len here from 1A Auto. We've got a little tech tip for you and it has to do with master cylinders. Let's get started.

Now, before you go ahead and install your brand new master cylinder, you're gonna need to make sure you get all the air out of the system. To do that, usually, you do a bench bleed and you would need a special kit that you can get that's going to go right on here. It's going to have some hoses that come up and then they're going to go back into the reservoir. The reason for that is because as you push in on this area right here, it's gonna force fluid this way and it's gonna come right out these areas right there. Once the fluid and air comes out, of course, you would want to catch it or whatever at that point, but once you release the brake pedal, it's going to try sucking back in this way right here. And, of course, if there was no lines that brought it back up into the fluid here, it's going to draw air back in and you're going to keep pumping and pumping and you're never going to get anywhere trying to bleed this out. With that said, if you are going to be replacing the master cylinder and you are just doing it in your driveway, you probably don't want to go ahead and buy the kit that you can get that will do this because it's going to cost you over $100 more than likely. 1A wants to help you save money, that's what we do. So, we went out, we grabbed a couple simple parts that you can find pretty much anywhere, and that's going to make this job much easier, much cheaper, and much more efficient overall. Now, what you need to do is you need to find fittings that are going to fit right into the master cylinder. Sometimes they're the same size. Sometimes they're different. So, make sure you bring the master cylinder with you when you go. You'll make sure that they screw right in. That's great.

The next thing we want to pay attention to is right inside where the master cylinder ports are. You want to see right down where that line's gonna connect onto and see what type of flare you're going to have to make. There's two different types of flares that you would have. You'd either have a bubble flare, which if you were to look in there, it would kind of look like it's inverted. And that way there, you can put a bubble flare into it, and then, of course, seat it. This one right here looks as though it has like a little cone, so that means that it's an inverted flare. With that said, that's the type that we're going to have to create. So, of course, we'll grab fittings that are meant for inverted flares. Now, we're going to set this aside and we're going to create the line. I just have some of this 3/16 brake line right here. This is going to work perfectly. And go just like that. You can start with whichever fitting you want to use. And now, we're going to flare this so it's an inverted flare like I said before. Let's get our kid on here. When you make a flare, you want to make sure that you have a little bit of the tube sticking out past. And a good way to judge how far you need it to go past is just by looking at the actual tool itself. It has like a little lip. If you line up the tube with that lip, it should have plenty sticking out. You don't want more than the lip though. Too much is not good either. Make sure this is nice and tight. Make sure this one's nice and tight. You would take your little bauble there, the adapter, slide it on there. And then, of course, we'll put our tool on. Now, we're going to watch right along the tool and we're going to make sure that this is crashing down and it's not sliding the tube out of the tool.

Okay. All right. That's completely down and I'm going to loosen it up. I'll remove the adapter. And now, we're just going to crush it in with the driver here, and that's going to make it inverted. Okay. That feels good. We'll get our tool off of here. There's our flare. There's our fitting. This looks great. That's going to go right into that end. So, the next thing we need to do is figure out exactly how much of this line we need to make it so we can go from the entry point where the line's going to go into the master cylinder, and then it's going to come up and around and into here. And when it comes around, you don't want it to just sit over the top. It needs to actually be physically down and inside that fluid. So, I'm going to make a little bend. And, of course, you can use a tool to bend it if you're worried about crimping the line. If you crimp the line, that's gonna, of course, cause a restriction and you're going to have a major issue. I'll just start this in just a teeny bit. And then I'm going to come up just over the top of it, and then I'll kind of guesstimate approximately how much I want to cut off so I can bring it right down in there. Get the tool ready. Let's see. Go right about here. I'll give myself a little extra. It's easier to trim some off than it is to try to put more on. Perfect. So, now, we would just bend this and like I said, make sure that it goes right down and inside that master cylinder as low as it can go. That looks very good. Now, you would tighten this. We'll tighten that with a wrench in a minute, but first, we're going to create this line the same exact way.

Okay. So, this looks great. If you were to look inside, you can see that those lines go almost all the way down to the bottom, but not necessarily the bottom. The only thing that's super important is to make sure that the ends are to be fully sitting inside a fluid at all times during your bleed process. So, now, we're just going to tighten these up. Use your corresponding wrench, whatever size fitting you used, it's gonna make a difference. All right. That bottomed out, teeny bit more, and that's it. Same thing over here. Okay. Now that we have this created and it's sitting in there perfectly, they are nice and tight and there's no way for any air to make its way in between this area right here, you would move along to bleeding out the system. To do that, you're gonna need to have this firmly secured in some way, you can either put it inside a nice vice like this one or, of course, in some instances, you could actually connect it right into the vehicle and it would be probably much easier that way. So, if we're going to go with the vice, just probably put one ear in here like this, make sure you get as much grip as possible, nice and tight. The next thing you would do would be to fill up the master cylinder. I wouldn't go all the way to the top, leave maybe like a 1/4 of an inch to an 1/8 of an inch there. And then after that, this is the super important part. You're going to want to push right here on this area. And when you do that, you don't necessarily want to use something that's hard, jagged, or even sharp. You don't want to use anything that's going to mar this up inside there because it could cause an imperfection, and, of course, it may not function properly. Also, if you were to use something sharp and you happen to slide out of the divot as you had already pushed in, you might mess up a seal. So, we'll stay away from using something like that.

Something that would be recommended to use would be like a nice piece of brass like this. Something that's much softer than the metal that's involved right here. So, in case you did happen to slip, you're not going to cause any damage and you could also use a wooden dowel. So, now, the method we're gonna use is put it right in the vehicle and we'll do it that way. Let's install this. It should go in just like that. Now, we're going to mount this in with those two nuts. Okay. That one is bottomed out. So, now what we're going to do is fill the master cylinder with the manufacturer-specified fluid. For us personally, on this vehicle, it's Dot 3. It's super important to pay attention to the inside of the master cylinder because there is two separate areas. They need to both be full. So, now, we have it securely mounted and, of course, it's filled while it's in the vehicle, we're going to go ahead and slowly push down on that brake pedal. As we push down, you're going to be seeing air getting pushed up through these lines, which, of course, you won't be able to see through the lines, but you will be able to see air bubbles coming up inside the fluid. I'm gonna go nice and slow, push all the way to the floor, pause, and then I'm going to release that brake pedal nice and slow as well. Every time I press, it's gonna force the air and fluid in. And every time I release, it's going to draw some of the fluid back this way.

So, now, I'm just gonna take a nice rag, put it under here so I can catch the majority of the fluid that might leak out. We're going to remove our lines right here because we've completed the bleeding process. And then at that point, we will, of course, connect these in and then bleed out the rest of the vehicle system. There we go. That one started right in there. All right. That one's nice and tight. Let's do the other one. So, now, we would just top off the fluid. We'll put on the cover. Now, we want to bleed the rest of the brake system.

Okay, friends. So, we had a lot of fun making this video for you. Hopefully, you learned a little bit of something along the way. If you did, drop me a like, and leave me a comment in the comment section, because I'd love to hear from you. While you're at it, why don't you go ahead and subscribe and ring the bell that way there, you can be kept up with all of our latest content? Thanks.

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