2001 honda civic brake line size

Back in March my dad’s 2001 Honda Civic developed a leak in one of the brake lines. The ensuing repairs ended up taking until September to finally finish, partly due to my free times and partly because I just had to replace more and more things. This is the story of what I had to do.

April

The brake line first started leaking in February or March, but because of the weather I didn’t get a chance to work on it until April. I found that the line going to the right front wheel was leaking. Parts of the brake lines are coated so they don’t rust, but other parts aren’t so they end up leaking after a while. Because of the confined space and corrosion, to loosen the fitting from the proportioning valve I used my little propane torch to heat them up. I tried sticking a bolt into where the fitting was to stop the fluid from all leaking out, but it didn’t work.

As I should’ve expected, using the torch to remove the fitting from the right front brake hose caused the hose to melt. Just the first of the parts I didn’t think I would have to replace.

All of the brake lines I’d dealt with in the past used the inverted flare on the end, but apparently Honda decided to use bubble flares on this model of Civic. I had to drive to work that evening to have a coworker flare the lines for me. Because of the path the right front line had to take I decided to do it in two pieces with a union between them, but unfortunately, I had cut the line just a few inches too short.

I didn’t want to have to have my coworker flare the line again so I rented a flare tool from Pep Boys, but it couldn’t do the right flare. Then I borrowed my shop’s flare tool kit, which is the same type as my coworker’s, but I couldn’t get it to work, and ended up just borrowing my coworker’s kit. Because of the awkward location of the proportioning valve it took me over half an hour just to get the new fitting to thread in.

Right around this time things got complicated when our Accord died. I had planned on working on it when I finished the Civic’s brake line but it took longer than expected and the Accord’s timing chain ended up failing and my parents had to buy a 2014 Civic.

Once I got the right front line finished, it looked like the front line from the master cylinder to the proportioning valve was leaking, so I had to replace that. I couldn’t get enough leverage with my wrench on the fitting and couldn’t use my torch so I had to use a cheater bar, and the only pipe I had was several feet long, so it looked a bit overkill.

After replacing the front master line, it still looked like it was leaking, so I decided to try making it again, because maybe I hadn’t quite gotten the flare right. At this point I changed to using copper line instead of steel, because it’s impossible to get the lines bent perfectly and they need some slight bending in the car to get them to line up.

May

At this point it was worth it to just buy a good flaring kit myself instead of constantly borrowing one. I bought the Mastercool 71475-PRC hydraulic flaring kit for about $275. May was a busy month so I ended up not getting much done, but I did try making the front master line for a third time because it was still leaking from the fitting at the proportioning valve.

June

The only reason I could think of for why there would still be a leak after three tries making the same line was that the proportioning valve had been damaged when I removed the old line. Replacing the proportioning valve then meant that I would have to replace all of the other lines going into it because disconnecting them would either cause them to leak or they wouldn’t want to thread in nicely with their old fittings. So now I had to replace the rear master line, left front line, and the front half of the right rear line.

I only did the front half of the right rear line because if I replaced the entire line I would probably have to replace the rear wheel cylinders, which would mean taking apart the rear drum brakes, which is another long and annoying job. Flaring the existing line on the car was not easy so I decided not to do the left rear line unless it didn’t go into the proportioning valve nicely.

July

I was having a lot of trouble getting all the new lines to thread into the new proportioning valve, just a few minutes would make my hand hurt. Another one of my coworkers, Tatiana, was able to come over and thread them in for me, laying under the car even while it rained without complaining.

I bled the brakes, and everything looked like it was good to go. The wheels went back on and the Civic was finally back on the ground for the first time in months and it was time for a test drive. I got in, pushed the clutch pedal…and it went right to the floor.

I could’ve expected this. Once brake lines get rusty it doesn’t take much for them to leak, and the hydraulic line for the clutch is basically a brake line. It must’ve gotten touched at some point, because at the lowest and rustiest point it blew out when I tried to take the car for a test drive.

Just like the brake lines, because of how rusty everything was I would have to replace almost all of the clutch hydraulic system. There’s a hard line running from the master cylinder, then a hose, then a hard line to the slave cylinder. The master cylinder is tucked into a nearly impossible spot to reach. It would’ve probably meant removing the windshield wipers to get to it to remove the line, so I decided to only replace half of the first line.

The strange thing about the clutch hydraulic circuit is that the first hard line is 1/4″ diameter tube, but the second is 3/16″, which is what the rest of the brake lines are. Because of this it took a lot longer to get it replaced than I would’ve liked. Unlike the brake lines, the clutch lines needed regular inverted flare fittings. Unfortunately, 12×1.0 inverted flare fittings for 1/4″ tube are extremely hard to find. I found some for 6mm tube, but that turns out to be just slightly smaller than 1/4″.

For the union where the original line was going to connect to the new line, I couldn’t find any metric unions of the right size, so I ended up going with non-metric fittings, making things even more complicated. As always, flaring the line still attached to the car was not fun.

Once I got the lines replaced, all I had to do was bleed the clutch, which can often be a long process. It’s not as simple as brakes where you just open the bleeder and pump the pedal, you have to open and close the bleeder every time you press and release the pedal. I bought a hand-pump vacuum bleeder when my regular bleeding method wouldn’t work, but I still couldn’t get any resistance in the clutch pedal at all.

Eventually I saw what looked like small bubbles leaking around the bleeder screw on the slave cylinder, which is not where the air is supposed to come out. At this point I decided to replace the slave cylinder because maybe it was somehow not allowing me to properly bleed the system.

I still couldn’t get the air out and was out of ideas, so another of my coworkers, Roland, came by after work to give it a try. We finally made progress when he decided to try loosening a fitting at the union in the first section of line, and sure enough, air came out and the clutch pedal immediately started getting better. Because the car had been sitting for months, it needed jump starting, and the brakes were rusted so it took a bit to break free to go for a test drive. Pretty quickly I found out that there was still a problem with the brakes, but not bad enough that I wouldn’t be able to drive it to work to finish up.

I bought a new battery, and it started up fine, but the charging system light was on, and the alternator was only putting out 11.5 volts, when it should be 14 volts. I was still able to drive it to work to finish everything up, though the brake pedal was a bit soft. When I first changed the right front brake line, because of how it’s routed I decided the easiest way to do it would be in two halves with a union connecting them, and I wasn’t sure if it was leaking or not. I brought it into the shop after work and confirmed that it was this union leaking, so I remade the first half of the line for the 3rd time.

The brake rotors weren’t in very good shape after sitting for six months, so I threw them on the lathe to clean them up. I also replaced the rear drums.

The last big thing I had to do to bring the Civic back to full working condition was to replace the alternator. Sitting for several months had cause it to no longer make as much voltage as it was supposed to.

For some reason, when Honda designed this engine, they made the belt tensioners use wing nuts instead of regular nuts. When everything gets rusty like they do here in New York, it gets a lot harder to work with the tensioners. Thankfully, my custom slotted socket works on wing nuts and I was able to loosen the alternator belt pretty easily.

Once I got the alternator out I removed the tensioner and cut the wing nut off, because under the wing but is a regular nut, making tightening the belt a lot easier.

The aftermarket alternator I got had a slightly different case that got in the way of the wiring harness bracket from the original, so I did a little cutting on the bracket to make it fit.

I was finally done with the major work, so it was time to give the Civic a good bath. Months of sitting stationary in the driveway meant it got really dirty, especially with a tree over it. I gave it a good scrubbing and it looks way better.

After all of that there were only a few little things left to do, like change the wipers and air filters. I also had to attach the clutch hose bracket to the transmission with some JB Weld putty because the bolt had broken.

So after all that I was finally done working on the Civic and it was a huge weight off my shoulders. It was $590 just in parts alone, but I was able to save my parents a lot of money, because labor at a regular shop would’ve been at least another $500 if not much more. The moral of this story is that if you go to replace one brake line, you’ll probably end up doing all of them and then some. If you actually read this whole post, thank you.

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-Dan

What is the standard size for brake lines?

Brake lines are most often 3/16- or 1/4-inch diameter and, while there will be no pressure difference between the two, there will be a difference in the amount of fluid delivered.

Are 3/16 and 4.75 brake lines the same?

The two most common brake lines found are 3/16"/4.75mm and 1/4". The smaller size is 3/16"/4.75mm brake line, CNF-3; and the larger size is 1/4", CNF-4. 3/16" is found on virtually all cars and trucks made in the world.

What size fittings are on a 3/16 brake line?

Brake Line Fitting: Assortment, 3/16 in OD Tube Size, 3/8" Thread Size, Steel.

How do I know my brake line fitting size?

First, use calipers to measure the thread diameter. The male threads will be slightly smaller than the nominal size, and the female threads will be slightly larger than their nominal size. Next, measure the pitch. For imperial sizes, count the number of crests within a ½” section and multiply it by two to get TPI.

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