As you are likely aware, your braking system an integral part of your vehicle’s performance and safety, and keeping it in working order is critical. Your brake lines, the veins of your braking system, are hydraulic lines that require specific parts and assembly to work safely.
Do brake lines need Teflon tape? The short answer is no–they do not. The more important point is that you should never attempt to use Teflon tape when attaching brake lines. Not only do brake lines not need Teflon tape, it would be dangerous to use Teflon tape on your brake lines in the first place.
If you’re considering using Teflon tape on your brake lines then you know you’ve got a problem on your hands. Let me explain a little bit about why this is a bad idea and what you should do instead of using Teflon tape on your brake lines.
Why Doesn’t Teflon Tape Work?
There are a couple of factors that make Teflon tape a lousy idea in brake lines. The first factor is that the brake fluid used in the hydraulic braking system is a solvent and will dissolve Teflon tape and other sealants. The second factor is that the parts on brake lines are manufactured to fit directly together with the use of flaring, pressure, and precise machining. We will look at why these factors eliminate the need for Teflon tape.
First Factor: Brake Fluid
If the brake lines are the veins of the braking system, brake fluid is the blood. Hydraulic systems use a fluid under pressure to move parts. This system is no exception.
Brake fluid is fierce. It is designed to withstand extremely high and low temperatures without boiling or thickening. It is also hygroscopic. That means that it pulls moisture from the air, which is why sealing the system is so important. It’s also the same reason that corrosion happens, requiring you to have regular fluid exchanges every 24,000-36,000 miles.
Brake fluid is also a solvent. That means that it will eat away at things like acid, including your hoses, seals, and Teflon tape. It also means that regardless of all the information on the mechanical aspects below, Teflon tape will not stand up to the very thing that makes the system work.
Pro Tip: brake fluid is also toxic, so always be safe when working with it. Accidental ingestion can be fatal.
Second Factor: The Parts Are Made to Fit Together
Brake Hoses
Let’s get the hoses out of the way first. Brake hoses are a flexible hose that connect your brake caliper to the metal tube. This tube makes up the bulk of your brake lines. The hoses are designed to be flexible because the movement of the wheels and suspension would destroy a solid line.
However, that doesn’t change anything about how their connectors should be treated when compared to the metal lines. Despite the different materials, the connectors should be treated the same as the metal lines. The hoses use copper washers at the end that connect the hose to the caliper. They use precise machining on the end of the hose that connects to the metal hose of the rest of the system.
These two factors eliminate any need for sealants like Teflon tape. If they leak, your hose needs to be replaced and not just patched.
Brake Line
The brake line is a mild steel tube that is easy to bend and flare, which leads from your master cylinder to your brake hose. These lines can sometimes get damaged and need to be replaced. They can come in straight sections, wrapped bundles, but also may be pre-bent to fit your vehicle.
If you purchase the bundles of tubing, be sure to know the size for your vehicle, usually 3/16” or ¼” or it will not match up to existing lines. It is important to remember that they must be bent and flared with specific tools for them to work correctly. This is not something you want to do with a screwdriver and pliers.
The Tube Flair
The tube flair sits inside of the tube seat, and the fitting sits flush inside of the female end. If you were to add Teflon tape to this fitting, it would not be able to seal properly in the union and would leak.
If you are getting a leak at this area in the line, it’s time to replace the line, flare, or fittings. Nothing you do or add will make a lousy flare work properly.
Brake Line Fittings
Since you are likely reading this because you want to repair your brake lines at home, you need to know that using plumbing compression fittings or single flair compression fittings on brake lines is not only unsafe, but it is illegal. These parts are designed for minimal pressures and not intended for the high pressure that takes place in this system. They will fail. Use only SAE certified flare fittings and unions.
It’s also good to note that the fittings are often a softer material than regular bolts. Go not use standard wrenches or pliers to remove them, or you risk stripping the heads. Instead, use a brake line wrench, also known as a flare nut wrench, or a line wrench. Here’s our recommendation for a brake line wrench.
On the outside, the brake line fittings look like any threaded fitting or coupler. When you remove them, however, you can see that what looks like a standard threaded connector is housing several parts designed to fit together with high precision.
Proper brake fittings are precisely machined to fit together. Adding Teflon tape keeps the parts from joining as they were designed to. You should always follow the specifications when installing them, as overtightening the threads will cause damage and a leak in your brake lines. If you would like to watch a video for a demonstration of how this works, click here.
When the threaded fittings are tightened into the female end of the union, they pull the line into the internal parts of the fitting. The angle of the threaded fitting matches up perfectly to the inside of the union.
The flair of the brake line then sits up against the curves and is pressed over them. This is why the flare is so important. If there is any gap or uneven surface, the union will fail, and the brake lines will leak. Teflon tape will not fix this problem.
You should never attempt to reuse old brake line flairs or fittings or modify them in any way. If they leak or do not fit, replace them, and save yourself the trouble.
Tools for Repairing the Brake Lines
Here are some specific tools we recommend if you choose to fix your brake lines yourself.
- Flaring Tool: You can get a flaring tool specifically for your line size. We like this one.
- Tubing Cutter: These are much safer to use for cutting delicate brake lines than a hacksaw. Check these out here.
- Brake Flaring Kit: Or you can pick up an entire kit here if you don’t have any of the tools already on hand.
But What About…
You will find many forums or posts online that suggest avoiding Teflon tape. You may see suggestions on the page to use “pipe dope” or a liquid sealant instead of Teflon tape on those very same pages. These products, while great for their intended purposes, do not work in this system.
The argument is that, because of the more fluid state of the material, it doesn’t inhibit the machined parts from matching up. At best, using these ideas don’t work and are a complete waste of time and money. At worst, they create gaps within the threads that make a place for the system to fail.
If It Leaks, Replace It
With all that said, can you use Teflon tape on brake lines? No. You cannot safely, nor should you attempt to use Teflon tape on brake lines. A brake system should not rely on anything to stop a leak. The system relies on pushing a solvent under high pressure in a closed system for safe operation, and Teflon tape will threaten the integrity of that system. If you have a leak, you will need to get it repaired ASAP.
