How to Replace Brake Master Cylinder 2004-08 Ford F150

Okay, friends, before we get started on replacing our master cylinder, something that you wanna think about is your bleeder screws. That's gonna be located on your calipers of your vehicle. Obviously, if your bleeder screws aren't gonna open up, you're gonna have an issue bleeding out the air from your brake system. Obviously, I have access to getting underneath the vehicle without having to remove the wheels. With that said, if you do have to remove the wheels, do it safely and then when you put the wheels back on, make sure you torque them to 150-foot pounds. With that said, one of the first things we wanna do is get off this bleeder screw cover. I'm just gonna take my small pocket screwdriver, get under there, pop it right off. It's always a great idea to spray down the bleeder screw and caliper area with a little bit of penetrant. That's gonna help you overall. So, now that we let that sit, I like to use a socket and a nice long ratchet. I'm just gonna kind of go back and forth with it a little bit to try to break it free. There we are. Just look to see if you have any fluid coming out. If you do, you know, it's not plugged up. I'm gonna close it and I'll do the same to all.

When it comes time to get your master cylinder out of the vehicle, something that's important to remember is that your brake fluid is not only toxic, but it'll also eat the paint off of your vehicle. So, with that said, you wanna make sure you have hand and eye protection, of course, at all times, during any of this work. I like to have a nice mat like this. This is something that's gonna be super absorbent and it's gonna collect any brake fluid that might come out. I'll put that right down here so it'll save the environment and, of course, my paint. The next thing I like to do is I'll grab a nice collection bucket, and I have a little baster here. And what this is gonna do is it's gonna draw the fluid out of here and then put it into my collection bucket for recycling. I wanna do this ahead of time because as I opened up those lines, the last thing I want is all this fluid to come dripping out and potentially get on the ground. Next, I always like to get the wiring off and out of the way. I'm just gonna take a small pocket screwdriver. And if you feel right along the bottom of this, you're gonna feel a little tab. Press up on that, give this a little wiggle, and remove it. I always check to make sure there's no funny colors. And, of course, this is the tab that I was talking about. Set this aside so it's as far away from brake fluid as possible. Let's spray down these fittings with some penetrant and let it sit and do its job.

Any time you're gonna be removing your fittings, it's always a good idea to use a wrench that looks like this. This is a flare end wrench and it pretty much covers most of the sides. If you were to use this an open-end wrench, obviously, you have more of a possibility of stripping out your fittings. With that said, I'm gonna use my 13-millimeter, put it right on here, and give this a couple of loving bonks just to try to break it free. Now, what you want to pay attention to when you're doing this is make sure that the line is not twisting as I remove this because if I turn this and it just starts twisting this line, obviously I just caused an issue and I'm gonna have to replace the line as well. There we are. There's one. Let's do the other one. There we are. Let's get these aside.

Go ahead and take these little plugs out of your new master cylinder and place them into your old. That's gonna help prevent a lot of this fluid from getting down onto the ground. Now I'm just gonna use a 13-millimeter socket and I'm gonna remove the mounting nut on this side and then the one on the other side and that's gonna be the only thing holding the master cylinder in. So, be prepared so we can remove it. Go ahead and grab onto this to, work it back and forth, and remove it from the booster. There it is, friends. Make sure you get all that brake fluid out of there before you recycle the unit. So, real quick, looking at the brake booster here, you can see that there's a lot of paint flaking up. The reason for that is because, like I said before, brake fluid eats away at paint and, of course, this is what's gonna happen. Well, if there's brake fluid coming down along the outside, there's also the possibility that brake fluid might've been making its way down along the inside of the booster. Just take a quick peek down inside there and make sure it's not full of fluid. If you see fluid in there, you need to get as much of it out as possible. Once you've done all that, go ahead and clean up the area so we can get off all this crud. We wanna make sure we have a nice seal. So I've got this cleaned up pretty good. You can tell that I don't have anything along here where the seal's gonna ride, which is internal there. I cleaned up the outer aspect as much as possible.

Now, before we get started on installing our master cylinder, there's something you need to think about. There's gonna be air inside the system. Even after you were to fill this up, there's gonna be air all inside there. With that said, you need to bench-bleed your master cylinder, which generally means just getting the air out of the system before it gets to your brake lines and potentially down to your ABS unit or even calipers. You can do that one of two ways. You can do it right in a vice like this, which would be easiest if it's just you. But if you have a second person, you can actually bring this right to the vehicle, mount it in, and then, of course, continue on with the next steps I'm gonna show you now. There's a brake master kit that you can get that's gonna make it so you'll be able to bleed out the air. It's gonna have a couple of one-way valves and it's gonna have tubes that come up from these and into the master cylinder. The reason for that is because as you pump on this right here or step on the brake pedal, it's gonna be forcing air and fluid out in through these and then back up and into there. We wanna keep doing that until you see no more air bubbles coming out of the master cylinder before you end up putting it into the vehicle/connecting the lines. If you don't have access to the master cylinder bleed kit because not necessarily everybody has one of those laying around, you could try to make something out of a couple of fittings that you find that fit inside the master cylinder and just a little bit of brake line.

What you would do, just take off your cap. You would line these up to their corresponding holes. Just this. I'm gonna screw this in so it's completely tight. Of course, I'll use a wrench at the end here. Do the same to both. I'm just gonna go ahead and tighten these up and then we'll continue. So, now what you would need to do now that you have your lines on here is, of course, fill it up with your DOT 3 brake fluid. You can take something as simple as a screwdriver, but just keep in mind that it has hardened metal on it and you don't wanna damage this area here. So, if you find something rubber or plastic or something that'll make a nice buffer, you can go ahead and press right on here. For me, personally, I'm gonna do this inside the vehicle because I wanna show you how to do it and it's much easier that way. So looking at your master cylinder, you can see that you have a nice seal going along here. Just double-check to make sure it's completely secured on the master cylinder like it is. Let's go ahead and line this up with the bolt holes and put it into the booster.

Now we're just gonna go ahead and put on the nuts. We'll bottom them out and then we'll torque them to manufacturer specifications. Work these to 18-foot pounds. Now we're gonna go ahead and fill this up with DOT 3 brake fluid. I'm just gonna go up to that maximum line. As we continue on and we do our bleeding of the master cylinder, you wanna keep frequently checking the fluid level to make sure it doesn't go low or even worse, empty. That looks decent right there. So, now that we have our brake fluid up nice and high and we have it so these lines are well below the level of the fluid, what we're gonna have is a second person inside the vehicle and they're gonna slowly pump that brake pedal. They're gonna press down nice and slow all the way to the floor. We're gonna watch for air bubbles. Once we stop seeing air bubbles, we're gonna ask them to release and then we'll repeat the process until we don't see any more air. Let's go ahead and give that a try. Go ahead and push it down.

All right. I can still see some air bubbles. That's great. Okay. Here we go again. So, as you can tell, we got much less air on that one. That's great news. We just wanna keep an eye on the brake fluid level because we don't want it to drop any lower than these lines inside the master cylinder. Go ahead and continue. We'll just repeat this process until we don't see any more air inside the master cylinder. All right. I'm gonna top this off a little bit here. Okay. Let's continue.

Now, the next thing we need to do is take off this rearward line. Once we have this off, of course, fluid's gonna come out. So you want it to catch as much of that as possible and then we're gonna go ahead and start in our original rearward line. Let's get this off of here. So, now I'm gonna start in this line just a little bit. I'm not gonna completely tighten it up, and I'll show you why in one second. We're just gonna have the person inside the vehicle. Go ahead and step down on the brake. But we're gonna wait on for one second. I need to get this started. You wanna make sure that you don't cross-thread this in. If it feels like it's having a hard time going in, there's a possibility it's cross-threaded, in which case, you could damage your line or even the master cylinder. Okay. So, I've got that bottomed out. Now I'm just gonna go ahead and open it up a couple of turns. And now we're gonna have the person step on the brake. Go ahead and step down on that and they're gonna hold it all the way at the bottom. At this point, it should be forcing fluid out around this area right here and it's also gonna force out any hair that might've gotten trapped on the end of this line. All right. Now I'm gonna close this. Okay. They can release. Okay. Now I'm gonna loosen this back up and we're gonna do this a couple more times. The key to this is to make sure you get out as much air as possible.

So, now we're gonna do it to the forward line. We're gonna do it in the exact same method. I'm gonna get this right out of here. Once again, there's gonna be a lot of fluid that comes out. Now I'm gonna start in this line. Go ahead and, please, step down on the brake. All right. So, I saw a steady stream of fluid, but then I also saw an air bubble. That's a good sign. That means we're getting the air out of the system before it makes its way down to the ABS unit. Let's go ahead and try that again. Okay. So, now we'll close this. The next thing we need to do is, of course, check our fluid. We wanna get it up to the maximum line. After I've done that, I'm gonna put my cap on it because DOT 3 brake fluid is hygroscopic, which means it's gonna absorb moisture from in the air. So, if there's any humidity, you could potentially contaminate your fluid or even any dirt or dust or anything like that. So, fill it up, put the cover on, clean up this area, and then we'll continue. Now that we have the area nice and cleaned up, let's go ahead and reconnect in our level sensor.

Make sure it's secure. It's definitely not gonna come free. At this point, what we need to do is start bleeding the brakes. To do that, we're gonna start on the right rear. All right. So, we made our way under the vehicle and we're at the right rear. There's the bleeder screw right here. We wanna open this up, but before we do that, we're gonna have the person up top pump up the brakes so they're nice and firm. As we open this up, we're gonna do it slowly so the fluid will hopefully come trickling out and land inside of our nice collection bucket here. Let's go ahead and pump up the brakes, please. All right. Let's open this up nice and slow. We're watching for any air bubbles at this point. You might not see any at first, but if you do this two or three times, what you'll probably notice if there's any air trapped up at the top, it's gonna make its way down here eventually. Let's go ahead and pump it again.

Okay. So, we've finished bleeding out this brake. We didn't see any air coming out at the end. It was just a solid trickle of fluid. That's perfect. The next thing you would need to do is move along to the left rear and then up to the right front and then finish off with the left front. That's the one that's closest to your master cylinder so that's where you end. After that, clean up your mess. If you took off the wheels for any reason, torque your wheels to 150-foot pounds, and then take it for a road test. Clean down this area and, of course, make sure we put our bleeder screw cover back on there. Now we can move along. Okay. So, our fluid level's full. Make sure we have the cap on here. Double-check to make sure you don't have any brake fluid on anything, especially anything painted or, of course, on the ground. Assuming everything looks good, take it for a road test.