Brake line flare

[John_C]

I installed a new master cylinder and the first time I pressed the brake pedal I felt something give. I crawled under the truck and found a nice hole in one of the brake lines where it had rusted through. The whole system is so rusty I'll probably need to cut it out with bolt cutters. None of the fittings come loose with wrenches or vice-grips. I've been doing research in the M37 manuals and on Utube on the materials needed and on how to make a double-flare. I know I need 1/4" line, but I've read that some military vehicles use a 37° flare rather than the typical SAE flare of 45°. What degree flaring tool do I need to buy? I know I can buy a brake line set, but I want to learn to do this myself.

Thanks
John, Grand Bay, Alabama

[NAM VET]

I am a few days ahead of your questions and decisions about your brake lines. With my motor now out, and everything accessible to me, I have ordered the cupro-nickel tubing from Fedhill, plus their tube nuts, and have the rental double flare 37 degree tool coming in a few days. He did suggest I re-use the connectors that are on the truck, as the only ones he can source are from China, and he says the OEM ones on the truck are a lot better. I am also going to re-do my vent lines, and my 5/15 gas line. I have the armor protective coils too.

here is some information for you....

http://store.fedhillusa.com/flaringtools.aspx

all the best....NV

[Kaegi]

you should be able to just buy long brake lines and use couplers to get the right length. I have never heard of a different flare on any dodge military 4x4. If it is different than standard automotive double flare I would like to know but I doubt it is. don't use the green stuff they sell in most parts stores now. it is terrible Chinese junk. my local napa stores still have the American made lines but usually not out in front. they are pushing the green Chinese junk out front. Or you might be able to pull your lines and measure the length on each section and order premade straight lines of cupronickel somewhere. I just did fuel lines in an M37 a month ago and was able to get the near exact length (had to cut and flare one piece) with off the shelf lines and I think the same amount of couplers as stock.

[06boblee]

Double flares are usually 45 degrees, a single flare is 37. Everything I've found on mine has been 45.

[hwo1990]

Hi John,
I sorted through the same kinds of questions. All the lines from the main frame tee are 1/4" nominal tubing. The short line from the master cylinder to the frame tee is 5/16. I looked into buying pre-made steel sets from vendors such as Vintage Power Wagons and Midwest Military but I wanted to learn how to do it myself. So for me the options were pre-made sets of steel with spring-coverings from the vendors, plain steel or coated steel straight lengths from places like NAPA, or the copper-nickel tubing. The tools available to make the double flares seem to vary greatly in cost and quality. I probably looked at the same websites and videos you have. It seems that getting a properly formed flare depends on a rigidly held and high quality flaring tool. I ended up using the copper-nickel tubing from my local NAPA store and a flaring tool from Sears. I found the flaring tool referenced in number of other car/truck message boards. The sears part number is 00947075000P Model #47075. I actually bought it from my local sears (before they closed) for about $65. It seems to still be available online. This tool in combination with the easily formed copper-nickel lines gave me good flares. The lines were also easy to form, probably too easy as I just shaped them by hand. They probably would look a little better if I used a tubing bender/forming tool, but you don't need to.

I did a spreadsheet comparing the cost of the copper-nickel lines vs straight steel and I've attached it to this post (and a pdf version too). I generated it using the line lengths listed in the parts list manual. The math said that one should be able to do all of the 1/4" lines with a single 25 foot roll of 1/4" tubing, and it actually worked out! This worked well and I used it to replace my fuel line also. The tubing is flexible enough that I actually "pulled" a single/continuous line from the fuel tank all the way to the engine compartment. Kinda like how you snake/pull romex wire. Not sure I do that again (one single length of fuel line) though cause it doesn't look very neat.

[R1830]

Thanks for sharing the brake line info hwo1990

[John_C]

Thanks for all the replies, especially hwo1990. I'll order a flaring tool today and buy the tubing and flare nuts locally.

John

[Explorer0863]

Great topic/information here. Just what I was looking for. Thanks!