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Audi A4 Front Brake Rotor Replacement
 
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Pelican Technical Article:

Audi A4 Front Brake Rotor Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$50 to $150

Talent:

**

Tools:

21mm socket, 7mm Allen, flathead screw driver, C-clamp, breaker bar, lug wrench, floor jack, jack stands, wheel chocks, torque wrench, bungee cord or wire coat hanger

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New rotors, mounting bolts

Hot Tip:

Pre-soak rusted bolts in penetrant oil

Performance Gain:

Car stops better

Complementary Modification:

Replace brake pads

Replacing your brake rotors is a very easy job to perform on your Audi A4 and a great way to get started on "Doing it yourself". In general, you should inspect your brake pads and rotors about every 25,000 miles, and replace them if the material lining of the pad is worn down enough to trigger the pad replacement sensor or there is less than a quarter inch of material on the pad. In reality, most people don't inspect their pads or rotors very often and usually wait until they see the little brake-warning lamp appear on the dashboard. It's a wise idea to replace the pads, and inspect your discs as soon as you see that warning lamp go on.

If you ignore the warning lamp, you may indeed get to the point of metal on metal contact, where the metal backing of the pads are contacting the brake discs. Using the brakes during this condition will not only give you inadequate braking, but will also begin to wear grooves in your brake discs. Once the discs are grooved, they are damaged, and there is often no way to repair them. Resurfacing will sometimes work, but often the groove cut will be deeper than is allowed by OEM specifications. If your pads are grabbing or pulsing when you come to a stop, there is a very good chance your rotors are warped and in need of replacement as well.

While this article will show you how to replace your front brake rotors without opening the brake lines now would be a good time to flush your brake fluid and bleed the system. I also recommend replacing the brake pads every time you replace the rotors. Please see our articles on these procedures for additional assistance.

First thing you need to do is get the car up on jack stands and the front wheels removed. Please refer to our article on jacking up your car for more information.

This photo illustrates the front brakes on the Audi A4.
Figure 1

This photo illustrates the front brakes on the Audi A4. You can see the rotor (red arrow), caliper (yellow arrow) and the brake pads (green arrow, one shown).

Begin by disconnecting the brake pad wear sensor from the harness (red arrow).
Figure 2

Begin by disconnecting the brake pad wear sensor from the harness (red arrow).

With the sensor disconnected release the locating plastic pin on the sensor from the mount (yellow arrow) by gently prying it out and then turn the sensor connection sideways (red arrow) and remove it from the metal mount on the caliper.
Figure 3

With the sensor disconnected release the locating plastic pin on the sensor from the mount (yellow arrow) by gently prying it out and then turn the sensor connection sideways (red arrow) and remove it from the metal mount on the caliper. Also remove the ABS wheel speed sensor from the mount (green arrow).

There are two 7mm Allen bolts holding the caliper to the mounting bracket.
Figure 4

There are two 7mm Allen bolts holding the caliper to the mounting bracket. They should be covered with plastic caps; if your calipers still have them remove the covers by gently prying them out with a flathead screwdriver (red arrow).

Use a 7mm Allen and remove the two bolts (red arrows).
Figure 5

Use a 7mm Allen and remove the two bolts (red arrows).

If you are reusing your guide bolts check them for wear and tear (red arrow).
Figure 6

If you are reusing your guide bolts check them for wear and tear (red arrow). It is a good idea to clean them up with a scotch brite pad and put a little white lithium grease on the smooth guide part of the bolt.

Place a large flathead screwdriver between the caliper and retaining clip (red arrow).
Figure 7

Place a large flathead screwdriver between the caliper and retaining clip (red arrow). Pry the clip from the caliper and set it aside. Use caution when removing the clip as it is under pressure.

Pull the caliper back off the rotor (red arrow).
Figure 8

Pull the caliper back off the rotor (red arrow). Sometimes the brake pad will stay in the mounting bracket on the exterior pad (yellow arrow) and sometimes it comes off with the caliper. If the caliper is really stuck, you can push it in on the piston side, compressing the piston and giving you more room to wiggle it off.

Tie the caliper up out of the way (red arrow) while replacing the rotor; never let the caliper hang by the brake line, this can cause damage to the line and fittings and may eventually lead to leaks and or brake failure.
Figure 9

Tie the caliper up out of the way (red arrow) while replacing the rotor; never let the caliper hang by the brake line, this can cause damage to the line and fittings and may eventually lead to leaks and or brake failure.

Use a 21mm socket and breaker bar to remove the two 21mm bolts holding the caliper mounting bracket to the wheel bearing housing (red arrows).
Figure 10

Use a 21mm socket and breaker bar to remove the two 21mm bolts holding the caliper mounting bracket to the wheel bearing housing (red arrows).

Audi considers these nuts and washers to be single use only and recommends replacing them after every use (red arrow).
Figure 11

Audi considers these nuts and washers to be single use only and recommends replacing them after every use (red arrow). Never install the bolt without the washer, as the torque value on the bolt will cause damage to the aluminum bearing housing.

Remove the caliper mounting bracket (red arrow) from the bearing housing.
Figure 12

Remove the caliper mounting bracket (red arrow) from the bearing housing. Use care, as the rotor is now free and you do not want it to fall on your foot.

There is no locating screw on the rotor.
Figure 13

There is no locating screw on the rotor. But it may be stuck in place by rust or corrosion. You can use a rubber mallet and tap the rotor. When hitting the rotor, you should always strike it on the bell (red arrow) and never the actual rotor face.

With the rotor free (red arrow), remove it from the hub (yellow arrow).
Figure 14

With the rotor free (red arrow), remove it from the hub (yellow arrow).

Make sure to clean the flange of the hub with a wire brush or wire wheel to give the new rotor a flat surface to mount to (red arrow).
Figure 15

Make sure to clean the flange of the hub with a wire brush or wire wheel to give the new rotor a flat surface to mount to (red arrow). Installation is the reverse of removal.

You may need to compress the caliper piston back into the caliper to get the caliper on the new rotors.
Figure 16

You may need to compress the caliper piston back into the caliper to get the caliper on the new rotors. This will cause brake fluid to travel back up into the reservoir and you need to make sure there is room for it (red arrow). Carefully clean around the reservoir before opening, as you do not want any dirt or debris getting into it. Be prepared to use a turkey baster or fluid pump to extract some of the brake fluid if necessary. Make sure whatever you use is clean; you do not want any contaminants getting into the fluid.

The new rotors will be thicker than the old ones and will necessitate pushing the brake piston back into the caliper to make room to get them over the disc.
Figure 17

The new rotors will be thicker than the old ones and will necessitate pushing the brake piston back into the caliper to make room to get them over the disc. Use a large C-clamp and one of the brake pads (red arrow) and compress the piston back into the caliper. Make sure to pump the brakes a few times before driving.

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