Home How-to Articles Video Series: How to Flare Automotive Brake Tube, Fuel Lines and Cooler Tubing

Video Series: How to Flare Automotive Brake Tube, Fuel Lines and Cooler Tubing

by Moses Ludel

Flare Tools and How to Flare Brake Lines

This in depth how-to HD video series covers brake tube flare types, flaring methods, flare tools and brake work safety concerns.  Attention focuses on the brake tube flare tools used for servicing production vehicles and building custom brake line systems. While many U.S. shops and DIY enthusiasts prefer the simplicity of pre-made double flared tubing with flare nuts already installed, the development of “prosumer” level flare tools and potential cost savings have encouraged the fabrication of brake lines using coiled bulk brake tubing and aftermarket flare nuts.

Vehicles use a variety of flare styles. There are U.S., Japanese, European and British Girling brake tube flares. This opening video introduces flaring techniques and how to identify popular brake tube flare types.  The common types of flares include the S.A.E. Convex and British Girling, the common U.S. and Japanese inverted 45-degree double flare, DIN and ISO metric bubble flares, each requires the right dies, adapters and tooling to produce an original equipment style flare.

Making your own steel brake lines with SAE/DOT approved brake tubing can be cost effective. Done properly, you can duplicate and restore chassis lengths of tubing to look and function like the original hydraulic brake system’s tubing. Some shops and consumers opt for modern NiCopp® and Cunifer (“Kunifer”) tubing or stainless steel as upgrades that work better around salted roads and corrosive environments.

This series will help you determine whether making your own brake lines is the right choice. You can consider the required skills, the necessary tool investment and whether the volume of work justifies the expense and learning curve.

Automotive tube flaring is an important repair and restoration need.  Salted roads and rocky trails raise havoc with brake and fuel tubing beneath the vehicle.  Transmission cooler lines, hoses and connections can fail.  After years in service, steel tubing will deteriorate.  Flaring brake tubes, fuel and cooling lines requires the right tools and safe practices.

This HD video how-to series starts with basic tools that can produce quality repairs if used properly.  Coverage includes tube flare types, step-by-step flaring techniques and the use of the holding and forming bar, arbor and sized double-flare adapters.  Included below is a discussion of brake work safety concerns and various service needs around hydraulic brake systems.

Tube flares can be made with basic equipment.  The tool at left would sell for $20-$40, depending upon quality and source.  The “adapters” are necessary for forming 45-degree double flare ends.  This is the traditional U.S. or S.A.E. double flare kit that forms common hydraulic brake flare ends on U.S. and many Japanese vehicles.  Always verify the flare type and fitting design used as original (OEM) equipment on the vehicle.  At right is the Ridgid #345 flaring bar and arbor press.  A modest upgrade to this level of equipment can make a major difference in the flare quality, tubing protection and repeatable results.  See details in the Part 1 video.

The Ridgid 345 bar and arbor kit is a professional grade tool used in commercial plumbing for single flare forming.  At left is the double or bubble flare adapter (from an Old Forge flare tool set) squarely pressing on the end of 3/16″ zinc coated steel brake tubing.  The 3/16″ tube is 0.028″ wall thickness, a common S.A.E. rated replacement brake tube.  Tubing comes in 25′ or 50′ bulk coils, and there is also “NiCopp” and stainless steel tubing available.  Make sure that tubing and brake fittings meet D.O.T. and S.A.E. standards for use on hydraulic brakes.  The tool is capable of double-flaring with the use of 45-degree adapters.  At right is the finished double-flare operation.   Double-flare adapters are available from Ridgid and several industrial and automotive aftermarket suppliers.

Ridgid offers the 33927 Kit (currently priced around $100 U.S.) that comes with a 345 bar and arbor press plus a tubing cutter and the Ridgid double flare adapter set.  This is a quality kit packaged in a case.  How-to flaring steps and important flaring details and tips can be found in the Part 1 video.

Lever Handle Turret Flare Punch-and-Die Tool

After years of struggling with split bar tools and dicey results, service technicians and serious DIY users wanted a flare tool that produced quality flares—quickly and repeatedly.  A decade ago, Harbor Freight offered a brake tube flare tool that won the attention of repair and restoration professionals.  While some find this flare tool’s bench vise mounting method limiting, most prefer its speed and sensible tube clamping method. Today, there are more than a dozen automotive aftermarket tool sources offering this tool under a variety of private labels…and for good reason.  See how the tool works and why we consider this one of the best “prosumer” values in brake and fuel line flare tools.

Nearly a decade ago, this now popular turret punch, lever cam flare tool showed up briefly at Harbor Freight.  After forty years of making tube flares, I immediately bought a kit.  Though Harbor Freight stopped offering this tool, more than a dozen other automotive aftermarket tool sources have offered this popular product.  The tool has design features found in higher end European flare tools, and for the DIY or small shop user, a prosumer level design like this works well.  Portable hand-pump hydraulic flaring tools are now gaining popularity, and this lever handle, manual turret punch tool has recently dropped substantially in price.

FLAREFORCE® Pneumatic Flare Tool for Brake, Fuel and Other Fluid Transmission Lines

FlareForce® is a well conceived, air-powered tool.  A repair shop working on brake systems with hydraulic tubing needs will appreciate the tool’s speed an portability.  The FLAREFORCE® can easily perform beneath the chassis either inside or outside a shop environment.  It is easy to envision the FLAREFORCE® at a Baja Race pit, King of the Hammers garage row or even on the trail.  Anywhere that 90 psi of reasonable volume shop or tank air can be mustered, this tool will make professional grade flares in seconds!  At right is the typical side view of a FLAREFORCE® formed flare, a lapped double inverted 45-degree flare—common to U.S. built vehicles from the 1930s to present.

At left is the uniform 45-degree inverted double flare that the FLAREFORCE® tool can consistently replicate.  There are many flare tools that occasionally make a perfect flare.  This pneumatic tool can repeatedly create a safe and trustworthy, precisely formed flare.  The flare at right is an ISO bubble flare formed with the first stage die in the FLAREFORCE® die slider.  When shaped with a first step 45-degree inverted flare die, the single step is more like a British Girling or SAE convex flare.  Compare this with a true DIN Metric type flare (squarely flat at the backside) discussed extensively at this URL page/article and within the tube flaring how-to videos.  Know the different flare types, flare nut styles and fittings that must be used with each flare design.

Mastercool® Hydra-Flare 72475 and 72485 Hydraulic Flaring Tools

Mastercool® has manufactured service equipment for HVAC/refrigeration and the automotive A/C service field for over 30 years.  For automotive brake and fuel tubing, the Mastercool® line of professional grade hydraulic flaring tools is portable and serves a variety of tube flaring chores. The 72475 and 72485 Hydra-Flare tube flaring sets update the popular Mastercool® 71475.  Designed for forming 45-degree inverted flares, metric bubble flares and specialty flare connections on automotive brake, fuel and transmission cooling lines, the Mastercool® Hydra-Flare tools feature interchangeable dies and adapters.  See the how-to video for details on the full range of adapters, dies and flare types.

Each Hydra-Flare tool set begins with the Hydra-Flare Yoke & Pump Assembly that works with the available adapters and dies.  Quick and portable, the Mastercool® flaring tools offer shops and serious DIY enthusiasts a user-friendly approach to making profession grade, repeatable flares.

The latest Hydra-Flare tool is the Mastercool® 72475 shown at left.  The 72475 set turns into a 72485 (at right) with the addition of 3/8″ and 1/2″ G.M. transmission cooling line adapters and die sets.

 The 45-degree SAE inverted double flare’s first step adapter works with popular SAE 3/16″ steel brake line.  Flares shape uniformly, and the I.D. of the bore consistently matches the I.D. of the inverted 45-degree double flare.  This provides unrestricted fluid volume flow while providing a full-contact seating surface of 45-degrees.

Tubing flares are easily repeatable and have a professional grade appearance.  The metric bubble flare dies form a flat back (DIN style) with a slight radius between the backside of the flare and the tube shank.  The radius reduces risk of fracturing the tube over time.  Be certain to use tube fittings that match the shape of the tube seat and flare angles while also allowing for the radius.

Tube preparation is crucial to the quality of a finished flare. The tube end is cut squarely with a pro-grade tubing cutter then deburred both inside and outside.  The 72475/72485 tools form an excellent 3/8″ fuel line double inverted 45-degree flare.

By contrast to the 3/8″ fuel line 45-degree inverted flare (left), the tube adapter at right forms a contemporary G.M. O-ring style fuel line flare.  The available force of the Hydra-Flare pump can form common automotive tube sizes to 1/2″ in steel, NiCopp® or cunifer, PolyArmour® and even brake grade (annealed) stainless steel as long as the wall thickness is not excessive.     

The G.M. fuel connector at left contrasts the unique G.M. transmission cooling line connection (right).  The 72485 set includes the G.M. transmission cooling line adapters and dies.  Both the 72475 and 72485 sets include the G.M. O-ring style fuel line adapters and dies.

Mastercool® offers a full line of flaring tools and tube forming/bending tools.  The 70069-A Tube Bender (shown above) is an all metal, multi-purpose 180-degree tube bender for 3/16″, 1/4″, 5/16″ and 3/8” O.D. tubing.  This easy to use tool eliminates guesswork while forming tube radii with defined radius degrees.  If your aim is to repair or build a quality brake, fuel or power steering/transmission cooling line system, see the Mastercool® product catalog at http://www.mastercool.com.  Shops, dealerships and serious DIY users prefer these tools.

Tube Shank Marring, Die Clamp Scarring and Holder Marks

The issue of jaw or die clamp pressure marking up the shank of the steel tubing is universal with both shop grade and DYI level flaring tools.  In our testing, the two tools that left the least impact on the tubing were, surprisingly, the Ridgid 345 manual flare tool set with adapters and the lever handle, vise mounted turret style tools with smooth channels in the die sets.  The Ridgid 345 bar uses fine, less angular gripping notches; the turret lever handle tools uses well-secured split block dies with smooth tubing channels.

When marring does take place on the tubing, Scotchbrite® fine pads can smooth out the roughness if appearance is a concern.  Better quality OEM-type steel tubing will usually have a thick enough electro-plated zinc coating to enable clean-up without scuffing through the zinc protective coat.

Note:  Most brake tubing replacement is due to rust and corrosion.  Zinc plating on replacement steel tubing is a rust preventive that must be intact.  Corrosion resistant NiCopp® (nickel/copper) and stainless steel (annealed) brake tubing has become popular for custom applications and even replacing OEM tubing.  The FLAREFORCE® can form precise 45-degree inverted double flares or ISO flares on either of these materials.

Rubber/Chemical Compatibility, Periodic Brake Fluid Changes and Choosing a Brake Fluid

Brake rubber parts are vulnerable to damage, wear and deterioration.  One of the quickest ways to cause brake rubber parts failure is exposure to petroleum or mineral base solvents, oils or compounds—including the popular products shown at left.  The time honored and safe substance for cleaning brake parts is denatured alcohol.  Always dry parts thoroughly before assembly…Periodic brake fluid changes can be done with a vacuum bleeder at the wheel cylinders and calipers, using the correct and fresh brake fluid.

Brake service work on cylinders and calipers will benefit from a castor base grease like Millers Red Rubber Grease.  Assembly of hydraulic cylinders and calipers can benefit from Raybestos BAF-12 Brake Cylinder Assembly Fluid.  Both of these products are harmless to brake rubber parts and recommended for the installation of caliper piston seals or brake wheel cylinder cups.

Always use the brake fluid type recommended by the vehicle manufacturer.  DOT 3, DOT 4 and DOT 5.1 are compatible glycol-based brake fluids.  (Use the recommended type, DOT 3 and DOT 4 are often combined ratings.)  Never mix DOT 5 silicone brake fluid with DOT 3, 4 or 5.1.  The difference between DOT 3, 4 and 5.1 is the boiling point, typically the higher the number, the higher the boiling point.  (Some DOT 4 racing brake fluids would be an exception, they have a very high boiling point.)  DOT 5.1 and DOT 5 Silicone have boiling points nearly the same but these fluids are not interchangeable, and they are not compatible.  If your system has recommended DOT 3 or DOT 4, adding or changing to a DOT 5.1 glycol based fluid is acceptable.  DOT 5 Silicone brake fluid can only be used by itself in a system completely free of glycol-based brake fluid.

At left is a contemporary Castrol brake fluid previously labeled DOT 4 GT/LMA.  The “LMA” stands for “Low Moisture Absorption”.  This LMA feature is desirable and allows consumers to use a DOT 4 glycol base fluid with more resistance to moisture.  (Moisture lowers the boiling point of brake fluid and causes system corrosion.)  DOT 5 Silicone Brake Fluid (shown at right) is hydrophopic—it will not absorb water.  Silicone brake fluid requires a system that is completely purged of all glycol based fluid and moisture before filling with DOT 5.  If there is previous moisture present, the DOT 5 silicone brake fluid will not absorb the moisture; instead, the moisture will form hazardous bubbles if the fluid reaches the moisture’s boiling temperature.  Never mix these fluid types.  For more details on DOT 5 Silicone brake fluid characteristics, visit the Clearco Products page at:   http://www.clearcoproducts.com/dot5-brake-fluid.html.

Warning:  Never use a mineral oil or petroleum product in a brake system designed for a castor oil/alcohol brake fluid (DOT 2), glycol-base brake fluid (DOT 3, 4 or 5.1) or a silicone type brake fluid (DOT 5).  Mineral and petroleum products can cause rubber to swell and fail…Gasoline or diesel fuel, WD40 or any other petroleum based product or solvent should never be used for cleaning or freeing up brake system parts that contain rubber.  Also note that brake parts cleaners often are intended for metal parts like brake backing plates and hardware—not for use within the cylinders or around any of the rubber seals!  Read labels carefully…There are isolated vehicle brake systems (exotic European models like some Citroen and Rolls-Royce cars) that specify the use of a special mineral oil brake fluid.  Always use the brake fluid type that the vehicle manufacturer recommends for a specific make, model and year vehicle.  On modern vehicles, the master cylinder cap often has an inscription that states the recommended brake fluid…If a product’s chemical compatibility with rubber is questionable, see the Mykin chart at: http://mykin.com/rubber-chemical-resistance-chart.

Identify the rubber type and recommended brake fluid type when working on brake systems.  Traditional brake seal and cup rubber is now being replaced by EPDM and other synthetic rubber materials.   Vintage vehicles with pre-DOT 3 fluid use a DOT 2 or equivalent brake fluid that is typically castor oil (vegetable base, not mineral) and alcohol.  This is why denatured alcohol is discussed in older shop manuals as a suitable “flushing” fluid for the brake system.   The castor oil will not harm rubber and neither will alcohol.  However, if denatured alcohol is used as a flushing agent, the lines and cylinders must be allowed to dry completely before replacing all rubber parts and replenishing the system with fresh brake fluid.  Drying can be sped up with the use of compressed air if the air is filtered and does not contain moisture.  Flushing with denatured alcohol is only done when all rubber seals are renewed after the flush and drying of the lines and cylinders.  If the cylinders are in good condition and rubber is known to be okay, leave them alone; simply exchange the brake fluid with fresh brake fluid.

Brake fluid changes get sorely neglected in the modern era, which means that corrosive moisture, a declining boiling point of fluid and brake fade can be an issue with hydraulic brake systems.  It is relatively simple to at least vacuum bleed the brake system periodically at the wheel cylinder or caliper bleeder valves.  Drawing fresh fluid through the system, from the master cylinder to the wheel cylinders or calipers, can at least remove the old hygroscopic (moisture absorbing) fluid and any debris.  Arguably, vacuum bleeding is more effective than power bleeding for purging contaminants from a hydraulic brake system.  Power bleeders apply pressure at the master cylinder, which can push debris to the edges of the wheel cylinders or calipers.  Vacuum bleeding draws old fluid through the bleeder valves and will suck out debris from within the cylinders or calipers.  If the cylinders remain assembled, vacuum bleeding will likely do a better job.

Footnote:  In the heyday of under-floorboard master cylinders, hydraulic brake system flushing annually was commonly recommended along with the replacement of brake cylinder rubber parts.  Vented master cylinders were notorious for absorbing atmospheric moisture, dirt and even road surface water.  DOT 2, DOT 3, DOT 4 and DOT 5.1 (not to be confused with DOT 5 Silicone) brake fluids are all hygroscopic:  They absorb water/moisture at the rate of at least 3% volume per year in the average climate and under normal conditions. A passenger car or 4×4 vehicle with the master cylinder mounted to the vehicle’s frame beneath the floorboard, like the vintage Jeep models and WWII to early Vietnam era military trucks, is highly susceptible to drawing moisture through the vented master cylinder cap, especially during stream fording or when the vehicle is stalled in body sill depth water!  Before the use of rubber bellows on master cylinder cover gaskets and other moisture barrier methods at the master cylinder cap, a periodic brake fluid change and hydraulic brake cylinder rubber parts replacement was considered an annual service task.

EIS master and wheel cylinder rebuilding kits were popular service parts in the vintage vehicle era.  Vehicle manufacturers recommended an annual brake system flush and rubber parts replacement.  See the vehicle manufacturer’s recommended fluid change intervals, usually one to two years on modern vehicles that use glycol-based (DOT 3, 4 or 5.1) brake fluid.  This kit (photo courtesy of a seller’s eBay ad) contains the typical service parts for an annual flush and rebuild of wheel cylinders on a 1930s to 1966 U.S. vehicle equipped with a vented-to-atmosphere, single circuit master cylinder.  Fluid quickly became moisture and debris contaminated, especially on earlier vehicles with the master cylinder exposed beneath the body!  Dusty roads and stream crossings were highly abusive to brake fluid, iron hydraulic cylinders and rubber parts.

For a better understanding of rubber types and their chemical sensitivity, see the Mykin Chemical website’s “Rubber Chemical Resistance” chart:  http://mykin.com/rubber-chemical-resistance-chart.  To better understand modern brake fluid characteristics and specifications, see this well written piece by Steve Ruiz at the Centric/StopTech site:   http://www.stoptech.com/technical-support/technical-white-papers/brake-fluid

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