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Brake Pads Replacement
 
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Pelican Technical Article:

Brake Pads Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$100

Talent:

***

Tools:

7mm Allen bit, flathead screwdriver, brake piston compressor, set of sockets

Applicable Models:

BMW Z4 Convertible (2003-06)
BMW Z4 Coupe (2006)

Parts Required:

Front or rear brake pads, brake pad wear sensors, brake fluid, brake cleaner

Hot Tip:

Stay clear of brake dust

Performance Gain:

Proper brake function

Complementary Modification:

Flush brake fluid. Replace brake rotors

BMW Z4 service brakes consist of hydraulic brake calipers and rotors, one at each wheel. When the brake pedal is pressed, brake fluid is forced out of the brake master cylinder and through the brake lines to each brake caliper. Pistons in the calipers push out and clamp brake pads against the brake rotors (or discs), thus slowing down the vehicle. A vacuum assisted brake booster multiplies the braking force exerted by the driver at the brake pedal.

The parking or emergency brake uses an entirely separate braking system. A pair of mechanically operated cables attached to the parking brake handle actuate parking brake shoes inside the rear wheel drums (which are integral with the rear brake rotors). I cover procedures for parking brake cable adjustment and brake shoe replacement in separate tech articles.

The brake pad wear warning system consists of electrical contacts installed in small cutouts in the left front and right rear brake pads. When brake pads wear down to the point that the tip of the contact touches the metal of the brake rotor, a warning light is illuminated on the dashboard. This usually happens when the brake pads are 2 to 3 mm thick (about 1/8 in). Usually, by the time the brake pad warning light illuminates, the driver becomes aware of the problem, and time is found for brake pad replacement, friction from the brake rotor has worn the top of the wear sensor down so that a new sensor is necessary. In order to avoid the expense of purchasing new brake pad wear sensors, check your brake pads every time you service your BMW Z4 and replace them as soon as they reach 3 mm thickness. As the wear sensor is only located on one brake pad per axle, 3 brake pads on each axle are not monitored by the warning system. This is why periodic inspections are required.

When replacing your brake pads, always replace both sides of the axle at the same time and have a new brake pad wear sensor handy. Even though the sensor may be reused, they become brittle and do not always fit tightly into new pads when reused.

In this article, I will show you how to replace brake pads on the front axle of your vehicle. Replacing the rear brake pads is similar.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

With the vehicle on the ground, loosen each wheel stud about 1/2 turn. This will help with removing them once the vehicle is jacked up.

Lift and support axle of vehicle you are replacing brake pads on. See our tech article on jacking up your vehicle.

Remove wheels on axle you are replacing brake pads on.

Using a flathead screwdriver, remove brake caliper anti-rattle spring by prying out while securing with hand.
Figure 1

Using a flathead screwdriver, remove brake caliper anti-rattle spring by prying out while securing with hand. The spring can pop off and go flying, be sure to hold it steady.

Open the brake caliper bleeder cover and remove the pad wear sensor (red arrow) wire from the mount.
Figure 2

Open the brake caliper bleeder cover and remove the pad wear sensor (red arrow) wire from the mount.

Pull brake pad wear sensor out of brake pad out of left side brake pad.
Figure 3

Pull brake pad wear sensor out of brake pad out of left side brake pad. Be very careful as sensor tends to break when removed. I like to use a pair of needle nose pliers to pull sensor out.

Using a flathead screwdriver, slowly press brake caliper piston in.
Figure 4

Using a flathead screwdriver, slowly press brake caliper piston in. This allows brake caliper to be pulled off brake rotor easily. I like to pry between the outer brake pad and brake rotor (red arrow). This way there is less chance of damaging the caliper piston. Forcing the piston back into the caliper will cause the brake fluid in the reservoir to rise. Be prepared to remove some fluid.

Remove rubber plugs from brake caliper mounting fasteners (red arrows).
Figure 5

Remove rubber plugs from brake caliper mounting fasteners (red arrows).

Next, using a 7mm Allen bit, remove brake caliper mounting fasteners (red arrows).
Figure 6

Next, using a 7mm Allen bit, remove brake caliper mounting fasteners (red arrows).

The last person to service the brakes on my Z4 subject vehicle used a thick grease on the caliper bolts.
Figure 7

The last person to service the brakes on my Z4 subject vehicle used a thick grease on the caliper bolts. It has hardened (red arrow) and made getting them out a little harder. I will have to clean this out of the caliper and off the bolt. Then lubricate the bolts with a silicone brake grease.

Working behind front strut, open plastic door (blue arrow) for brake pad wear sensor electrical connector.
Figure 8

Working behind front strut, open plastic door (blue arrow) for brake pad wear sensor electrical connector. Disconnect brake pad wear sensor electrical connector by pressing release tab (red arrow) and pulling it straight apart.

Pull the wiring pad wear sensor wiring harness out of the mounts (red arrows) and lay it aside.
Figure 9

Pull the wiring pad wear sensor wiring harness out of the mounts (red arrows) and lay it aside.

Remove brake caliper from mounting bracket.
Figure 10

Remove brake caliper from mounting bracket. Do not allow brake caliper to hang from brake hose. Secure to vehicle using a piece of a metal coat hanger. Remove the outer brake pad from brake caliper.

Then press piston back into caliper using a brake caliper piston tool or a C-clamp (red arrow).
Figure 11

Then press piston back into caliper using a brake caliper piston tool or a C-clamp (red arrow). Open the bleeder screw and catch the escaping brake fluid in a suitable container when compressing the piston. Remove the inner brake pad. Clean the brake caliper and the brake caliper mounting bracket. Install new brake pads into caliper and caliper mounting bracket. Install caliper to mounting bracket and tighten fasteners. Then install rubber plugs. Connect pad wear sensor electrical connector and route wiring harness as before. Install brake pad wear sensor into brake pad. Install brake pad anti-rattle clip by pressing into caliper and pushing down to confirm it is properly seated. Once calipers are installed and fasteners are tight, press brake pedal to pump brakes up. Once brake pedal is hard to push, install wheels and check brake operation. Bleed brakes if necessary.

If you are having trouble with a brake pad warning light and the sensors and pads look OK, you will want to test the circuit.
Figure 12

If you are having trouble with a brake pad warning light and the sensors and pads look OK, you will want to test the circuit. Follow the steps previously mentioned in the tech article to unplug the sensor in question. Then jump terminals 1 and 2 (green arrows) together using a fused jumper wire, (photo shows harness side of connector). Turn the ignition ON and OFF, then back ON. If the light goes out the sensor is faulty. If the light doesn't go out, leave the jumper wire in place and perform the same steps on the next sensor. If you jump out both connectors and the light doesn't go out, the problem is likely in the harness. I find most issues are with the harness from the front brake pad sensor up along the body. You will have to test the wires to determine which part of the harness is faulty. You could run new wires to test, which is quickest. Or you can test the wiring using a DVOM measuring Ohms. Once the problem is found, replace the faulty wires or connection.









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Page last updated: Fri 12/9/2016 03:00:46 AM