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Brake Line Replacement
 
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Pelican Technical Article:

Brake Line Replacement

Jared Fenton

Time:

2 hours2 hrs

Tab:

$60

Talent:

****

Tools:

11 mm flare nut wrench, 13 mm wrench, power bleeder

Applicable Models:

A6 2.7T (1997-04)
A6 2.8 (1997-02)
A6 3.0L (2002-04)
S6 4.2 (1997-04)

Parts Required:

Brake lines

Hot Tip:

Use a flare nut wrench to prevent damaging lines

Performance Gain:

working brakes

Complementary Modification:

replace brake pads and rotors

One of the most often overlooked maintenance items is an inspection of the flexible brake lines that connect from the main chassis of the car to the brake calipers. These lines are made out of rubber and have a tendency to break down and corrode over many years. With some of the older A6s now reaching over 100K miles, the rubber lines should be carefully inspected every 10,000 miles or so. They can exhibit strange characteristics, such as bubbling and expanding prior to actually bursting. Needless to say, failure of these lines is a very bad thing, as you will instantly lose pressure in one half of your brake system.

Faulty brake lines in the front of your car can cause all sorts of steering problems when braking. It is common for bad hoses to cause a car to pull from side to side under heavy braking. Bad hoses allow pressure to build up in the caliper, but sometimes do not release this pressure properly when the pedal is released.

The first step in replacing your lines is to elevate the car. Remove the wheels, as this will make it much easier to access the brake lines. See our article on Jacking Up Your Audi A6 for more information. To prevent a large amount of brake fluid from leaking out, I recommend pushing the brake pedal down just to the point of engagement, and blocking it there using a rod or stick of the right length propped against the driver seat. If you do this, you will lose less brake fluid, and also less air will enter into the system.

Make sure that you have some paper towels handy, as there will be some brake fluid that will leak out of the lines. Brake fluid damages paint. Keep in mind that any amount spilled on the paint will permanently mar it. If you do get some on the paint, make sure that you blot it, and don't wipe it off. Be aware that your hands may contain some brake fluid; don't touch any paint on the car with your hands.

The brake lines themselves can be very difficult to remove. The goal of this job is to remove the lines without damaging anything else. In this case, the easiest thing to damage (besides your paint) is the hard steel brake lines that connect to the flexible rubber lines. These lines have relatively soft fittings on each end, and often become deformed and stripped when removed. The key to success is to use a flare-nut wrench. This wrench is designed for jobs like this one where the fittings are soft and might be heavily corroded. The flared end of the wrench hugs the fitting, and prevents it from stripping. It is very important to only use one of these wrenches, as it is very easy to damage the fittings using a regular open-end wrench.

The other disastrous thing that can happen is that the fitting can get stuck to the rest of the hard line. The fitting is supposed to turn and rotate on the end of the line, but sometimes it becomes too corroded to break free. When this happens, the fitting and the line will usually twist together, and it will break the line in half. Be careful when you are removing this fitting to make sure that you are not twisting the line.

One other thing that's helpful is to spray the area down with a good quality penetrant oil a day or two before doing the work. This gives the oil time to work itself into the threads and loosen things up. I've found that Aerokroil made by Kano Labs works especially well in these instances.

Installation of the new lines is straightforward and the easy part of the job. Before you start attaching the lines, make sure that you have the correct ones for your car. There are a few different types, and a few different lengths, so make sure that the ones that you are putting on are the same length and have the same fittings as the ones that you are removing. If the line you install is too short, then when your car goes over a bump, it may stretch and break the line. Once the new lines are installed, you'll need to bleed the brake system of air. See our article on Bleeding Brakes for more information.

When it comes to replacing brake lines, many people install stainless-steel braided lines on their car. The rumor has it that the stainless steel sheath keeps the rubber line from expanding under pressure, and actually delivers better performance than the standard lines. While this reasoning sounds good at first, it's mostly hype. The stainless steel braided lines are often made of the same rubber underneath, and are simply protected by the outside sheath. Even if the sheath were tight enough and strong enough to prevent the lines from expanding, it really wouldn't make a difference in braking. Even if the lines expand a little, the resulting pressure that is exerted at the caliper will be almost the same. The stock lines already have an internal metal layer that stiffens them, so the gain is minimal.

On the other hand, I still recommend that you install the stainless-steel lines on your car because the outside sheath protects the lines from dirt, grime, rocks, small animals, and other things you might run over with your car.

The other thing that might warrant your consideration is the label of DOT (Department of Transportation) certification. With the original rubber lines, they were required to be certified under a certain set of specifications dictated by the DOT for use on US highways. Often, the stainless steel lines are aftermarket components that are not DOT certified, and are subsequently listed for "off road use only." In reality, these lines are more than adequate for use on your car, and any concern over the use of them is not really necessary. However, for those who want to be absolutely sure and certified, there are manufacturers who will make DOT certified stainless steel lines, but they are usually more expensive than the non-certified ones.

Front: Shown here is the upper connection on the front brake lines.
Figure 1

Front: Shown here is the upper connection on the front brake lines. Use an 11 mm flare nut wrench to loosen the nut (green arrow). Once loose, remove the line from the compression fitting. The new line installs in the same place.

Front: The lower brake line fitting is nearly impossible to get a picture of.
Figure 2

Front: The lower brake line fitting is nearly impossible to get a picture of. You'll need to feel for it behind the strut and use the 11 mm flare nut wrench to remove it, as shown here (green arrow). Be sure to let the line drain of old fluid. The new line installs in its place.

Front: Once the new brake line is fitted, be sure to bleed the system as shown here.
Figure 3

Front: Once the new brake line is fitted, be sure to bleed the system as shown here. See our article on Bleeding Brakes for more information.

Rear: Shown here is the rear brake line (green arrow).
Figure 4

Rear: Shown here is the rear brake line (green arrow). The lines are the same for both left and right sides.

Rear: Use the 11 mm flare nut wrench to loosen the nut (green arrow).
Figure 5

Rear: Use the 11 mm flare nut wrench to loosen the nut (green arrow). Once loose, remove the line from the compression fitting. The new line installs in the same place.

Rear: The flexible line attaches to the brake caliper with a 13 mm banjo bolt (green arrow).
Figure 6

Rear: The flexible line attaches to the brake caliper with a 13 mm banjo bolt (green arrow). Be sure to replace the two copper washers on either side of the banjo bolt. These washers seal the line in place.

Rear: Once the new brake line is fitted, be sure to bleed the system as shown here.
Figure 7

Rear: Once the new brake line is fitted, be sure to bleed the system as shown here. See our article on Bleeding Brakes for more information.

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Page last updated: Mon 10/23/2017 03:20:57 AM