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Brake Line Replacement
 
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Pelican Technical Article:

Brake Line Replacement

Jared Fenton

Time:

2 hours2 hrs

Tab:

$100

Talent:

****

Tools:

Jacks, jack stands, T30 Torx driver, 11mm flare nut wrench, pressure bleeder, penetrating oil, catch tray for brake fluid, a means of blocking the brake pedal down.

Applicable Models:

Porsche 955 Cayenne (2004-08)
Porsche 955 Cayenne GTS (2008)
Porsche 955 Cayenne S (2003-08)
Porsche 955 Cayenne Turbo (2003-08)
Porsche 955 Cayenne Turbo S (2006)

Parts Required:

New brake lines, brake fluid

Hot Tip:

Spray the brake fittings with penetrating oil before working on them

Performance Gain:

Better braking performance

Complementary Modification:

Change 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 Cayennes now reaching ten years old or 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 Porsche 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 when 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 depressed.

The first step in replacing your lines is to elevate the car. Remove the wheels from each side of the car, as this will make it much easier to access the brake lines (see our article on Jacking Up Your Cayenne for more info). 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. 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 anything near the 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 crescent 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 good quality penetrating 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 to work 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).

I recommend using stainless steel lines. The outside sheath of the stainless steel lines give protection from dirt, grime, rocks, small animals, and other things you might run over with your car.

Front Brake Lines - Left and Right Sides: Shown here is the front brake line (green arrow) on the Porsche Cayenne.
Figure 1

Front Brake Lines - Left and Right Sides: Shown here is the front brake line (green arrow) on the Porsche Cayenne. You'll find that if you turn the wheel fully outward as shown here, it will provide easier access to the brake line connections.

Front Brake Lines - Left and Right Sides: Begin by removing the T30 Torx bolt holding the retaining bracket to the suspension upright as shown here.
Figure 2

Front Brake Lines - Left and Right Sides: Begin by removing the T30 Torx bolt holding the retaining bracket to the suspension upright as shown here.

Front Brake Lines - Left and Right Sides: Once the bracket is removed, pull the rubber grommet surrounding the brake line (yellow arrow) out of the ring on the bracket (green arrow).
Figure 3

Front Brake Lines - Left and Right Sides: Once the bracket is removed, pull the rubber grommet surrounding the brake line (yellow arrow) out of the ring on the bracket (green arrow). You'll need to transfer this bracket to the new brake line.

Front Brake Lines - Left and Right Sides: Shown here is the lower brake line connection where it meets the hard line going to the brake caliper.
Figure 4

Front Brake Lines - Left and Right Sides: Shown here is the lower brake line connection where it meets the hard line going to the brake caliper. The green arrow points to the 11mm nut that holds the two lines together.

Front Brake Lines - Left and Right Sides: Use an 11mm flare-nut wrench (green arrow) to loosen the fitting enough to un-thread it by hand.
Figure 5

Front Brake Lines - Left and Right Sides: Use an 11mm flare-nut wrench (green arrow) to loosen the fitting enough to un-thread it by hand. Be prepared for brake fluid to pour out of the line. Wait until it stops draining brake fluid until moving on to the top connection.

Front Brake Lines - Left and Right Sides: As you can see here the upper part of the brake line (green arrow) snakes under one of the wheel liners.
Figure 6

Front Brake Lines - Left and Right Sides: As you can see here the upper part of the brake line (green arrow) snakes under one of the wheel liners. It is possible to access the connection without having to remove the entire liner. Simply remove the two lower T25 Torx screws at the bottom edge of the liner and pull it back.

Front Brake Lines - Left and Right Sides: With the liner pulled back, you can access the 11mm fitting.
Figure 7

Front Brake Lines - Left and Right Sides: With the liner pulled back, you can access the 11mm fitting. Once the fitting is disconnected, remove the brake line from the frame around the fitting and install the new lines. Take extra care when threading the fitting back inside. If you encounter any resistance, stop, back the thread out and check that it is seated correctly. Sometimes the threads can take a little time to get seated correctly.

Rear Brake Lines - Left and Right Sides: Shown here is the rear brake line on the Porsche Cayenne (green arrow).
Figure 8

Rear Brake Lines - Left and Right Sides: Shown here is the rear brake line on the Porsche Cayenne (green arrow). The procedure for replacing the rear lines is similar to the front, although there are a few key differences.

Rear Brake Lines - Left and Right Sides: Begin by using an 11mm flare-nut wrench to loosen the lower fitting at the brake caliper as shown here.
Figure 9

Rear Brake Lines - Left and Right Sides: Begin by using an 11mm flare-nut wrench to loosen the lower fitting at the brake caliper as shown here. Loosen the fitting until you can un-thread the remainder by hand and separate the rubber portion of the line from the metal hard line. As before, let the line drain before moving on to the top fitting.

Rear Brake Lines - Left and Right Sides: Shown here is the location of the 11mm fitting at the top of the brake line (green arrow).
Figure 10

Rear Brake Lines - Left and Right Sides: Shown here is the location of the 11mm fitting at the top of the brake line (green arrow).

Rear Brake Lines - Left and Right Sides: Use a flare nut wrench to loosen the fitting at the top of the brake line.
Figure 11

Rear Brake Lines - Left and Right Sides: Use a flare nut wrench to loosen the fitting at the top of the brake line.

Once you have replaced all of the lines, you'll need to bleed the brake system of air.
Figure 12

Once you have replaced all of the lines, you'll need to bleed the brake system of air. The best method for doing this is using a power bleeder such as the one shown here made by Motive Products (see our article on Bleeding Brakes for more information).

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