Mazdax605 PowerDork
10/19/20 8:11 a.m.

Hey fellow GRM leute,


So I've never been good at brake line flaring. I don't do it often, so that's is probably why. Also I have crappy tools, but yesterday I borrowed a fancy hydraulic flaring tool from a friend. He gave me a crash course on using said tool, and it seemed easy enough. I'm attempting to repair a couple of rotted lines on my sons 04 Pontiac Vibe. The lines all look good because they are coated in a plastic coating, but the rear line just before it switches to the rubber was rotted and leaking on the passengers side. This car was purchased a year and a half ago from a friend, and has been sitting, but on pavement most of the time. It is an older car that lived here in New England, so it's a little crusty, but not terrible.


I bought some line yesterday, and formed up a maybe 10" section to splice into the offending line on the passengers side. Cut the old line on the car, removed some of the rubberized coating, placed a fitting, and flared it. Installed a union, and then using one factory end of the line I bent up, flared the other end, and all seemed well. Then moved to the bleeder on the wheel cylinder to bleed the line. Promptly broke the bleeder of course. A trip back to the local parts place to get a new wheel cylinder, shoes, hardware, and drums, because why not do it all on your kids car, right?  Got the new stuff all installed , and asked one of my kids to come help me bleed the brakes by being the pumpman. Just as we started I noticed a puddle forming, and wouldn't you now it was from the flare I made on my new line. Not the one on the existing line on the car that was a little tricky getting the tool on, but rather the one I made up on the bench. Wtf am I doing wrong? I seem to have maybe a .250 batting average on flares. Might get me a decent contract in MLB, but when you're spending all day in the garage on a Sunday it mostly gets you enraged. Now I need to get back out there tonight or one day this week, redo that line, and then move to the other side. I hate rusty cars!!! I hate brake lines!!



maschinenbau (I live here)
maschinenbau (I live here) GRM+ Memberand SuperDork
10/19/20 8:25 a.m.

I learned to take extra care centering the die in the line. Both for the die and the cone-shaped thingy. If you get either step off-center too far, it won't make a good seal. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/19/20 8:56 a.m.

It's like painting, the prep is critical. Make sure it's a square cut and that you've chamfered both the inner and outer lips of the tube.

Also, you can buy pre-flared lengths of brake line at NAPA with the fittings installed. It's a great shortcut.

codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand UberDork
10/19/20 9:19 a.m.

One thing I discovered while doing was that the first time I put a flare together I needed to tighten the flare nuts more than I expected.  It's as if the flaring tool was only getting the shape 95% correct and the last 5% of the forming needed to be done with the flare nut.

Streetwiseguy MegaDork
10/19/20 9:26 a.m.
codrus (Forum Supporter) said:

One thing I discovered while doing was that the first time I put a flare together I needed to tighten the flare nuts more than I expected.  It's as if the flaring tool was only getting the shape 95% correct and the last 5% of the forming needed to be done with the flare nut.

Yes, you do need to tighten more than expected.  It's a steel on steel union.  You need to tighten/loosen/tighten a couple of times to bed stuff together.

10/19/20 9:41 a.m.

You making the correct flare for the job? Bubble or double flare? Not all tools do both flares,



boxedfox (Forum Supporter)
boxedfox (Forum Supporter) Reader
10/19/20 10:54 a.m.

In reply to Streetwiseguy & codrus (Forum Supporter):

Nowadays I keep a few known good brake lines with M10 inverted flare fittings in the toolbox. Whenever I flare a new fitting, I'll put the new line on one of these pre-built lines and crank it down with a flare nut wrench so the newly flared end has a chance to seat. Then I'll take it all apart and put the line on the car.

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) GRM+ Memberand MegaDork
10/19/20 11:28 a.m.

I wish I had something to add but I feel lucky every time I make a non-leaker.

10/19/20 11:32 a.m.

Just finished the task of installing all new brake lines on the 1959 F2 truck. flare 4 re-dos total before the system was bled. About par for the course.  Did not have to re-do any of the actual lines, just messy cutting of the flare at the very end and re-doing while fluid pours out all over me..

Mazdax605 PowerDork
10/19/20 2:11 p.m.
NOHOME said:

You making the correct flare for the job? Bubble or double flare? Not all tools do both flares,



Well one of the flares is fine, and the other one is not. The flares I made look like the factory ones(well probably not as nice, but same style).

Vigo (Forum Supporter)
Vigo (Forum Supporter) MegaDork
10/19/20 2:18 p.m.

Im in the 'tighten it some more' camp. What Codrus said is correct in that it's not a perfect flare from the tool that makes it seal, it's a good enough flare from the tool that allows the fittings to evenly smush the crap out of it until it conforms to the fittings. So being tight enough is more important than most people realize, i think. If it is steel-to-steel as mentioned, put a little grease on the threads of the nut and put it back together tighter. Unless you have really nice flare wrenches, you will usually  start seeing your flare wrench getting sketchy on the fitting before you actually wreck the threads of a steel-to-steel connection. So, if you weren't even a little scared about rounding off your fitting, that means you can tighten it some more. cheeky

Mazdax605 PowerDork
10/19/20 2:25 p.m.

I also have questions about the brake line union I bought at the parts store. I mean it says brake line union on it, and it seems to work, but the leak I'm having is on one side of that union. I feel I made teh same flare on both lines to this union, but one is a leaker. Is it possible the union is to blame?

HotNotch New Reader
10/19/20 2:30 p.m.

The trick is to use Nickel - copper (NiCopp) line if you can.  Far easier to fabricate and flare, and I haven't had to redo a bad flare yet since I switched.

AngryCorvair (Forum Supporter)
AngryCorvair (Forum Supporter) GRM+ Memberand MegaDork
10/19/20 2:47 p.m.

In reply to HotNotch :

I just went 3-for-3 leak-free with NiCopp last weekend. First time using NiCopp. Also first time with no leaks. So yeah, I guess NiCopp FTW. 

rattfink81 Reader
10/19/20 6:22 p.m.

I made 3 lines for my raider(the Dakota copy) using the Nicopp. Had to do standard double flare on one side of the line and bubble on the other. I did use my buddies fancy Mac flare tool but it was easy and no leaks. I haven't flared a brake line in atleast 10 years.  

Napa sells pre flared lines but my lines were all too long or short for any of them and the fittings were not the right size.

HotNotch said:

The trick is to use Nickel - copper (NiCopp) line if you can.  Far easier to fabricate and flare, and I haven't had to redo a bad flare yet since I switched.

This needs to be repeated. Several times. 

I replumbed most of SanFord with this. Not one screwed up flare. Not one leak. 


Tony Sestito
Tony Sestito PowerDork
10/19/20 8:28 p.m.

NiCopp line is amazing. Used it for the 1st time over the summer on the Power Wagon. I never want to use anything else ever again. 

On the flares... 
I've seen some cars that have both double and bubble flares! Take my old '97 Dakota; that had all sorts of different BS going on. American Standard double flares, metric bubble flares, and who knows what else. I'm guessing since it's a Toyota/GM vehicle that you should have either Japanese double flare lines or bubble flare lines. Also, like others said, if you are making your own flares, and they are the right kind of flare, sometimes it takes a few times to get them to actually seal up. It happens to all of us. 

Nitroracer (Forum Supporter)
Nitroracer (Forum Supporter) UltraDork
10/19/20 8:58 p.m.

I replaced my cheap AutoZone style flaring tool with a nicer Eastwood unit and I haven't had any issues making a flare since.  Do I forget to put the fitting on before making the flare?  Of course, we all do that.


wawazat Dork
10/19/20 9:16 p.m.

Another vote for NiCopp here.  I also have the turret style flaring tool sold by just about everyone (Summit, Jegs, Eastwood, etc) that really works well assuming off car flaring.  I cut, deburr in/out, and spray some WD-40 on the tube end and die face.  Three pulls on three positions (seat tube and die, form flare, fold in to double flare) and its done.  Just remember to put on the tube nuts before the second flare!

jerrysarcastic (Forum Supporter)
jerrysarcastic (Forum Supporter) Reader
10/20/20 2:53 a.m.

Yet another vote for NiCopp, which I’ve used for both brakes and cooler lines. It just seems to bend up so nice, and despite being a total noob I’ve yet to have a leaky connection.  I don’t know if I’ve been lucky or what, but all I’ve ever had was a cheapo HF-grade flaring tool and that’s been fine for NiCopp.

I don’t see it mentioned yet but I think it’s a real plus (along with now easy it is to work with) that they’ll never rust or corrode, so in theory the NiCopp lines will last a lifetime... as long as you don’t forget fittings before you flare.  ;)

kevinatfms GRM+ Memberand Reader
10/20/20 6:23 a.m.

If he has a bubble flare in a double flare end it wont seal and leak. Make sure its the correct flare type before you go all gung-ho on things. They are two entirely different flare types which do not mix together.

APEowner GRM+ Memberand Dork
10/20/20 9:13 a.m.

To see if the issue is the union turn it around.

How is the final pressure on the fancy tool you borrowed controlled?  If it's user dependent you may had just not crushed enough. 

A conventional flare seals on the internal face so that needs to be smooth with no cracks.

The fitting presses on the outside of the flare and if there are significant burs on the outer surface it can result in uneven pressure on the inner face causing a leak


Mazdax605 PowerDork
10/22/20 10:49 p.m.

Took a half day off from work today to work on the Vibe. Took out the offending new line. Looked it over, didn't see anything wrong with it. Made a new one using some nicopp line on the say so from many people. New line leaked too. Looked at the flares I was making and they were all garbage.


Called my friend who owns the fancy flaring tool I was borrowing. He walked me through it all again. I was doing it like he showed me, but nothing was correct about it. Went over his house and showed him what it was doing and my results. Turns out that the 45 degree cone was messed up and he said it was because of me, but I don't know how it could have been as I did it like he showed. He machined the cone, and I ordered him a new one anyway. He was having trouble with the flares too, but less so than I was. Not sure why though as I was doing it just like him. 


Ended up with using the first line I made, and it seems to be leak free now. Not sure why. Moved over to the other side, and couldn't get the line on the wheel cylinder loose. Don't want to move forward unless I can get it taken apart. I hate rusty cars!! 

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