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Project Difficulty
Estimated Project Time
8-10 hours
Required Tools
  • Basic Hand Tools
  • Wrench Set
  • Socket Set
  • Flare Nut Wrenches
  • Brake Cleaning Spray
  • Penetrating Oil
  • Brake Fluid
  • Blake Bleeding Kit
  • Water
  • Safety Glasses
  • Absorbing Mats (optional)
  • Head Light (optional)

Video Transcription

Hey guys, I'm Kevin Tetz working with LMC Truck to bring you some technical information and how-to videos that are going to help you with your truck project.

In this video, we're going to be dealing with the brake system on a 67 – 72 GM truck and we'll show you how to replace the existing steel lines with a Stainless Steel pre-bent Brake Line Set. Now all of these lines are pre-bent very accurately to match the factory bends and although it might look like a nest of snakes right now, the process is quite simple and we're going to walk you through it.

LMC Truck also offers brake hoses and rear brake hoses for both leaf spring and coil spring vehicles, as well as all the hardware that you're gonna need to mount your hard lines to the frame rail and the chassis. Now although we're not dealing with it in this video, LMC Truck also offers wheel cylinders and drum brake rebuilding components as well as a Master Cylinder and we'll show you proper installation techniques for a master cylinder in this video as well.

Now the benefit of pre-bent brake lines is pretty darn obvious right here. This is a very difficult bend sequence to re-create. Now pre-bent brake lines mean all you have to do is go to or your LMC Truck catalog, pick them out, order them and they'll show up on your doorstep.

Now, let's talk about tools. You're going to need basic hand tools, a combination wrench set and some sockets and socket wrenches, but this, this is necessary. These are flare nut wrenches or line wrenches and you need them to effectively disconnect your brake lines without tearing them up. Some brake cleaning spray is nice to have around and so is some penetrating oil for the rusty frozen fasteners that you're inevitably going to run into, as well as you're going to need some brake fluid, that's kind of obvious.

Here's something that you're going to need if you're replacing a master cylinder like we are. This is a Master Cylinder Bleeding Kit. You can pick these up at any auto parts store and you've got to properly bleed the air out of the master cylinder and we'll show you how to do it. As far as safety goes this is not a crazy dangerous project, but you are working under the truck, so have some safety glasses on hand and get some gloves since you're going to be handling brake fluid.

Now if you've just drug your truck out of the field, some insect spray may come in handy as well and here's another thing too. Some water, just plain water will neutralize the brake fluid in case you spill it on paint. You can keep it from eating the paint off your vehicle. Now since brake fluid is going to leak out some absorbing mats are easy to find at the parts store and they'll come in handy you can keep things clean and environmentally friendly. A head light, as goofy as it looks, is a really good idea and keep your hands free to work while you're underneath the dark vehicle. Now the LMC Truck catalog is really nice to have around because the illustrations are so accurate, it can actually act as an assembly guide.

Now on a difficulty scale, it's not that difficult, I'm gonna give it a 3 1/2 out of 5 but you might want to set aside an entire weekend to do it, so you can take your time and methodically do things the right way. Now let's take a look at the project.

Now between the obviously leaking master cylinder with the paint stripped off the firewall and the spongy brake pedal that this truck has, the master cylinder is done, it's on its way out. [Lift sound] Right here, obviously, we're missing a retaining clip but right here, the brake hose is almost worn through, and here again on the flexline it's frayed and that's just dangerous. The steel brake lines, they're rusty and it's just too important and they're too easy to replace, so that's what we're going to do. Like we said these lines are very accurately bent so I just compare them to the lines on the truck and it gives me a roadmap to replace them one at a time. I've laid them out here, it makes perfect sense. Except for this guy, which is bent like this for the purposes of shipping. So, here's how to bend it back straight because it goes along the frame rail without using any expensive tools. What you want to do is put the bend focused on the floor, so you're actually using the floor for support. Don't bend it like this, because you could possibly kink the line. With a push on the floor, just gently, slowly, bend it back straight. Kind of using different areas of the bend as support. One more bend here. Alright, so it's not perfectly straight but it doesn't have to be, it's clamped to the C channel frame rail, so now we're ready for that piece to go in the truck.

One more thing LMC Truck also offers junctions and unions. We've got one here but we're going to try to re-use our originals and show you how to do the same. Now the back of the truck's the easiest to get to, so we're going to start here and these are just little tabs. Bend them back. Alright, that's loose. [Music & Ratcheting] There you go. [Music]

Clean this off so we can get a wrench on it. We'll remove the line from the wheel cylinder, that doesn't want to cooperate, boy! These lines are rusted up. OK, now you want to try and keep from tearing up your brake lines, but right there that shows us exactly why we need to replace them. It's just rusted, it's just rusted. Still gotta get this guy out of the wheel cylinder. It's pretty easy right now, and for some reason it's bone-dry. Out of there.

Alrighty. Now this bolt right here is just a retainer for the flexline and the union and we're gonna remove it all. We don't even have to disconnect those lines. We can take it all off as one unit since it's all getting replaced. [Ratcheting] That goes away and we're going to keep the fastener where it belongs, so we don't have to track it down later. There's a clip right here that we're going to get rid of, that holds the flexline to the frame rail, and the new clip comes with the brake hose.

Alright. Now we can undo this guy, but since we're replacing everything, I'm just going to try and cut it right here. We can still use it as a template if we need to, it's just gonna be much easier, and that bothers me that there's no fluid in the rear circuit. No wonder this things brakes were goofy.

Now there's several of these clips that connect the brake lines and the fuel lines to the frame rail and they're easy to remove, they're easy to get to. You can re-use if you want to, or you can just get new ones from LMC Truck. Even though I've already pre-soaked this with penetrating oil it's just hard to move it. I think that's it! Ah, I think we got it. No, it broke off. The bolt actually twisted in half. I don't care how it comes off, but it came off. Point is, it's been rusting since 1971 so I guess it's earned its, its stubbornness.

Here's the union we need to keep it but here's where your line wrenches come in handy. We want to keep the flats intact so we can we re-use this piece, so your line wrenches will do exactly that.

We're finally getting some, finally getting some brake fluid out of the brake system. There we go.

Alright now, if you're breaking this project up into afternoons or days on a weekend. Now might be a good time to go ahead and replace what you just pulled out. That's what we're gonna do. We're gonna pre-assemble this "T" for the rear axle right here, but before you start putting stuff together, get use to doing this.

We've got some break cleaning spray. Don't assume that there's nothing in the lines, don't assume that just because they're new, that they're perfect. Something may have crawled up in there or maybe debris from shipping. [Air-blowing] Blow them out, make sure they're good and clean. That way you don't end up troubleshooting a problem, that you don't need to deal with. A little bit of preventive maintenance. This also, kind of puts the exclamation point on the need for safety glasses too. Protect your eyes.

Get that guy out of the way. We know that this goes here. I just want to make sure these are seated, I'm not even going to really snug them until we get them clocked in the right place, and by the way never use Teflon ever on brake lines. They're designed to be a press-fit Teflon will seal the threads but it won't seal the circuit. Alright. That goes there. Yep, right over there.

What we're going to do is start these threads, just to give us some stability and a little bit of leverage, to put their lines in their final place. Good enough.

These are brass fittings, you kind of get one shot, so you want to make sure the threads are seated and started properly, so you don't strip them. OK, there it is.

You start to thread it by hand and then you take your line wrench. I'm not going to fully tighten this until I've got all the connections made, but I am going to run it in which takes a while when you're doing one flat at a time. Alright, that's good enough for now. Now we can put this slowly and carefully in behind the tabs. [Music] There it is. Alright, snug right there. [Music] There. Now, place our lines in there.

With everything kind of in a place you can use the tabs as leverage to get everything set where it needs to be. There we go. There [Music] There. [Music] There. [Music] [Tapping] A little bit of love to the axle tabs. [Tapping]

Alright, now we can tighten up our union over here, work our way forward. [Music] I can give the lines a nice snug with my flare nut wrench. We'll check them again when we leave the system, we'll just check for any fluid leaks.

We don't want to over-tighten them. There nice! Now I've blown out my line, but I've got the rubber cap back on it. Protecting it just in case as I'm feeding it in the frame rail I jam some crud up into it, and have to clean it out all over again. Alright, that should be about it. Alright so my hard lines coming through there, I connect now to my flexline.

Alright now with that snug, go up in there and I've got a clip that'll slide back there, to lock that circuit right into place. This is our retaining clip it's going to lock it in place. It just gets tapped in. [Tapping] There it is. Now we're just going to loosely bolt in our brake line retainer and we're able to reuse one of the original ones. I'm going to just hand nut it. We'll snug it down, we'll secure, ensure of the placement of the rest of the lines. Alright, since this retainer was rusty, we're going to use one of the new ones from LMC Truck. [Ratcheting] Alright, keep that a little bit loose, in case we need to move the lines around.

OK, underneath the crossmember of the truck I'm up here and got my head light on and even with the line wrenches I still had to cut this line because a lot these nuts are rounded off. However we can still save the unions and the T fittings and get everything out of here and still retain the shape of the brake lines that were pulling off, so we can compare them to the ones that were putting on. Now even the lines on the junction up here is so hamburgered up I can't even turn it with a pair of pliers, so I'm just gonna cut them. The ever alarming, nearly dry, brake circuit.

OK, now we can get rid of these old lines. Out with the old. There's those guys. Now this is tight. [Tapping] There, okay. There [Ratcheting]

We're going to keep that bolt, and so right now we're just going to go ahead and replace our flexlines with the copper washer on either side of the banjo bolt. We know it's in the right way when the nub on the top, falls into the channel on the caliper. There we go. Perfect. Good gosh, there. [Ratcheting] That's going to weep from the caliper for a little bit. Right now we're rescuing our copper washers again but, I also want to make sure that my banjo bolts are good and clean. We've got a fluid passage right there, brake fluid has to go through. So we're good to go. Set our banjo bolt in, make sure our copper washer is in place. Use a little bit of brake cleaner, and wipe the crust off of it, because for some reason this side is a little bit more dirty. Alright, perfect, it can go there, the way to connect that up with the other line.

Give this a snug for now. Now our truck is rusty, there's no fresh paint anywhere but if your restoration is fresh and you've got brake fluid dripping down here could eat the paint or even wrinkle the powdercoat, so that's where water comes in.

This is just H2O and I'm literally dousing it and rinsing the brake fluid off with water. Water neutralizes the brake fluid and will stop its corrosive action right in its tracks.

Now we're going to install the retaining clips that weren't even here when we started. [Tap] Just like that. As we pulled the old lines off the truck we compared them to the new pre-bent stainless steel lines and it made it very easy to choose which ones to go back in and where to put them. Just like the others we'll thread them in a fingertip first and then come back and snug them up later when it's all fit.

OK, we're going to reuse this original union to complete our brake line circuits and this is where the line wrenches will save you parts and money. Look at that. Thank you line wrench.

OK, this is our rear circuit going all the way to the back. This is the union we just borrowed and it's going to the front, actually transitions into the backside of the master cylinder, so we just gotta get it threaded by hand. There, and now this side. Alright. Maybe it'll thread in, maybe it won't. Sometimes, sometimes you get lucky, sometimes you've got to pre-bend the lines just a bit. I think, we got lucky. Alrighty. I'll tighten them up in a little bit.

So this is our new stainless line that goes to the rear circuit and this is where it connects to. This goes up to the backside, the rear bowl of the master cylinder, the dual reservoir.

This brass T-fitting is new from LMC Truck and it's going to connect this line, to the line that goes to the front caliper on the driver's side, to this line here, that goes up to the front reservoir on the master cylinder, that we're replacing that line as well, so we're going to put a brass fitting in and replace the upper lines, finger-tight into the brass T, and connect driver's side caliper line. Alright, now our T is in there.

This guy's ready, now we're ready for these 2 new lines that go up to the master. (Master Cylinder) [Lowering truck] There we go. OK, it's kinda what I figured we’re bone dry in the back, but we've still got some fluid in the front. Just using a bulb extractor, getting my brake fluid out. A turkey baster also works for this. It's a cheap tool.

This is actually made for battery fluid, so we know it's going to withstand the brake fluid corrosiveness. Interestingly enough our brake fluid is an interesting brown color which means it's soaked with water and needs changing anyway.

We got some brake fluid on the paint, so I'm going to soak it with the water because we don't want to damage this awesome paint job. Alright, now we're gonna, oh yeah, there we go.

We're taking the Master Cylinder off, because we're putting a new one on. Alright, there's that. [Music] There. Since we're here and they're unhooked at the bottom, we'll get our portioning valve out of here too. Give it a good inspection, clean it up.

So, when replacing a master cylinder, you've always got to perform a bench bleed. It's a pretty simple procedure, but it's absolutely necessary. Basically, what you're doing is purging the air out of the fluid passages, the master cylinder itself, so that it pushes pure fluid and not air bubbles into the brake circuits front and rear.

The Master Cylinder Bleed Kit comes with several different fittings and since they're plastic be very careful tightening them in. You want to make sure that you get an air tight fit, but you don't want to strip the threads.

OK, I've got 2 hoses for the front and rear reservoirs and the clip that's gonna hold the hoses in. We go to the rear, go to the front, we'll bring these guys around and connect them to plastic fittings on the side, and make sure there's no kinks. Alright. Now there's a new seal on every bottle of brake fluid. I like to use the smaller bottles of brake fluid that way if I don't use it all, it sits on the shelf for two years and gets a bunch of moisture in it. Doesn't cost me a whole quart of fluid, I just use what I need.

So now use a flat screwdriver and actuate the master cylinder just like what happened if you push the brake pedal inside the cab and right now it's full of air. You can see the bubbles. You can see the fluid going back and forth between the bowls and the reservoirs rather and the fittings. The foam is what you don't want to see. So, if it starts to foam up like that it's just a bunch of air bubbles so give it a little bit of a break.

Let the foam dissipate. The rear circuit reservoir, the back one it's looking pretty good. I don't see any bubbles but the front we're still working. OK I'm moving slower, works better and I can see just a couple little more bubbles coming up through that hose. I'm not seeing any more bubbles. Alright with our master cylinder fully bled it's going to stay right here till were ready to install it.

We're going to re-use the original proportioning valve for this truck. Since we're not changing the brakes up, drum in the rear, disc in the front. The prop valve it's a big dumb animal unless it's damaged, it'll probably still work just fine, but we do want to clean a little and give it a good inspection.

Here's what we're looking for. Now you want to look down into where the fittings go, the internal flare, well it's brass, you don't want any damage on that. Ours look good. The backsides look good. So now we're going to give it a quick shot with brake cleaner.

Important to wear glasses because this stuff can backfeed. Yep OK, we're good here. I just want to make sure all the fluid passages are clear, and everything is hunky dory. It's happy.

One more thing, take my bleeder valve loose. [Spraying fluid]

OK good, good we're back flushing and it's clear. Oh, there you go. [Spraying fluid] Alright, now we're going to blow it out with some air then we're ready for reinstallation. [Blowing air]

Alright, we'll throw our bleeder valve back in, and while we're here, we're going to install the lines. There we are. Here's a pre-bent line for the rear brake circuit. Snug as a bug in a rug. Alright now these guys, just kinda hang together like that. Then we can see where they go together like that and meet the circuits down underneath the cross-member.

Alright now we'll install the proportioning valve and get ready for the master cylinder. We're on the homestretch. Alright I'm gonna feed the lines down right through here, carefully. It's a bit of a jigsaw puzzle. Not too bad.

Now we'll loosely mount the prop valve on the firewall. Just like that. Here's a line from the rear reservoir of the master cylinder that goes back to our rear brake circuit and I'm going to snug these in place right now. After I get everything snugged in, and after we make sure that there's no leaks in the system, then I'll clamp it all down to the frame rails and cross members. I want to be able to get access in case I gotta give these an extra little twist. There's that. Alright, so the rear circuits complete.

Now, I'm gonna hold my brass T in place with an adjustable wrench and use the line wrenches to tighten up the line fittings. I'll get the top line from the front reservoir of the master to the crossover for the front circuit, and I'll give it one little extra bit of love. OK. Now everything's good and snug.

Now, I'm going to cap off these guys real quick, so we don't lose any more fluid on the installation. There's that, drain it back in. Now we can put this sucker in its new happy home.

Now to make sure the brake plungers in the right place and it is. Oh yea, were home.

[Ratcheting] Leave that a little bit loose till we get our lines hooked up. Throw something down here to catch any brake fluid that might fall out and we're gonna get rid of our plastic fittings. I kind of hamburgered them up tightening them a little too tight, but they're plastic fittings. Now we're going to lose a little bit of fluid, not a whole lot. Just make sure the threads are caught there. OK, there it caught. Thank you, thank you threads, thank you line wrench. Thank you brand new fittings.

Now we'll tighten the master cylinder against the firewall, and give these a final snug. [Ratcheting] There we go. That's snug. Now that we've got everything bolted in, all the lines are threaded. Now I can go back and give a nice final good and tight snug on all of these line fittings with my flare nut wrench.

OK, there it is. Man that looks fantastic, except for the fact that I've got brake fluid all over my inner fender. Now the paint's garbage on here anyways but if you had a nicely restored vehicle with good paint, here's where your bottle of water comes in handy. Just neutralize all of that brake fluid.

Now keep in mind of course we need to bleed the brakes on this truck, but we've just shown you that it's an achievable an easy goal to completely replace all the original vintage carbon steel lines on this truck and install new stainless steel brake lines sets, that not only fit great but they look great as well. Keep in mind you can look through LMC Truck catalogs or go to for other ideas on how to increase the performance and the looks of your 67 to 72 Chevy pickup.

I'm Kevin Tetz thanks for watching.