|Tech Article Title
Brake Pad Replacement for 100 CS
The brake system is a major safety component of your vehicle, therefore attention to specific details and mechanical experience is required to do a safe job. Years of training and experience can be found at your local mechanic shop in case something goes wrong with your own attempt. Improper removal or reassembly could result in damage to the vehicle and injury to others on the road. This manual is written as a helper when changing the front brake pads on your Audi. It was written for the Girling brake system but might fit others as well. Some mechanical skills are required for this job. Please be safe and proceed with caution.
Required tools and parts:
- Brake Cleaner Spray
- Floor jack
- Two Jack Stands
- Lug Nut Wrench
- Set of Brake Pads
- Anti Squeaking Compound
- Flat Head Screwdriver
- Torx Wrench Set
- Two Feet of String
- Two old Towels
- Wire Brush
- Four New Torx Caliper Holding Bolts
- C Clamp or Brake Piston Tool
- Hammer to Tap Things Loose
- Jack Stands
First of all: Safety is your number one concern when doing this procedure! If you don't feel sufficient enough in your mechanical capabilities take the car to a shop and have them do it. There is too much risk and danger involved when the brake system has been tampered with by an inexperienced mechanic. If you feel confident about your mechanical skills let's go ahead and start the job.
Immediately before we begin you must park your car on a hard level ground; preferably a garage so you can work in a quiet place. Then place the transmission shifter in park (or in reverse if you drive a manual) and engage the emergency brake firmly. Meanwhile open the hood by pulling the hood release handle which is on the drivers side near the door hinges. Also leave your front windows down in case you need to get to the inside of the vehicle but leave the keys in the ignition in the OFF position.
At the same time you could place a piece of wood under the one rear wheels to make sure the car won't roll away when the front of the vehicle is raised and you are working under the car. Next, open the hood by pulling on the exposed safety release hitch near the Audi rings. Raise the hood and engage the service position by pushing in the red release button in the rod. This will allow you to raise the hood straight into the air. In the meantime, use the lug nut wrench to loosen up the five lug nuts on both front wheels. They must be loose before the vehicle is raised.
Now comes the floor jack, roll the jack to the drivers side door and look for the lifting supports. Those supports are a few inches under the Audi signs on the undercarriage of the frame. You will safely raise the vehicle without causing damage to the frame with the jack. This would also be the lifting point when changing a flat tire. Now roll the floor jack under the car and begin to raise the jack to engage the support. Check that the support is positioned in the middle of the jack's lifter. If the position is right, continue raising the car. The jack should be at a 90 degree angle to the car for best results. Stop lifting about a foot off the ground. That is the perfect height to do all the repairs. To be on the safe side, place a jack stand next to the floor jack, and extend it as far as possible. Now slowly lower the car onto the jack stand.
With the wheel now raised off the ground; remove all five lug nuts and pull the wheel towards you to remove it. Remember the rim is really heavy so make sure you have a steady lift position. Lay the wheel away from the work area and place the lug nuts in it so they do not get lost.
You should be able to see the strut tower with the brake rotors and calipers now. Rotors will last forever if the right brake pads are used and replaced at the right time. New rotors are 25mm thick and should be used once the old rotors reaches a thickness of 23mm. If you replace one side of the brake system, you should change the other side also to ensure safety and equal braking power. Brakes are your lifeline, so what you pay for them is worth what you will get in safety. The front brakes receive the most wear and will require more checks and maintenance than the rear ones.
When replacing pads or rotors the fluid in the brake fluid reservoir will raise since the pistons are pushed back into the calipers and the fluid will travel back towards the reservoir. Use a syringe to remove some excess brake fluid and place an old towel around the reservoir to avoid spill and paint damage. Brake fluid is highly toxic and will harm you, therefore handle it with care.
To remove the caliper from the rotor you will need to disconnect the brake pad sensor cable connection. The sensor cable has a plastic frame that fits into a groove on the strut tower. Towards the engine side of the tower you will see the connector. Now, press the "M" shaped pin of the connector together and pull the connector upwards, it will come right off and the cable going to the top will hang loose around. Now use the screwdriver to get the old connector frame out of the groove by prying the black plastic extension off. It may brake, but that won't be a problem since it will be thrown away. Turn the connector a half turn and it will come out and hang on the brake pad.
Now use the screwdriver to remove the holding spring of the caliper which is the big "W" shaped metal piece facing you when looking at the brake assembly. Remove it by placing the screwdriver under it and pulling slowly but with lots of force towards you. It will be easy to remove once one side is loose. Also remove the rubber protective caps on the inside from the caliper holding screws towards the front. There are two of those rubber plugs on the calipers. You can trace it down by following the brake pad sensor cable. It will go towards it.
Find the right size torx wrench to remove the two holding bolts. Sizes are different on some calipers and special caution should be considered. Bolts should be replaced with new ones on reinstallation of the calipers on both sides. Be really careful when removing the bolts. There's a reason they had those rubber plugs on them: to protect from rust and road dirt. If you don't have the right size wrench for the bolt or no firm grip on it you may round off the bolt which will cause a lot of problems. Therefore use the right size wrench. If there is dirt on the bolt use the brake cleaner spray to clean them. Start with the lower bolt first and then remove the upper one. The caliper will be loosely sitting onto the front rotor after that. Carefully pull the caliper upwards towards the spring. The inside brake pad will stay in the caliper pull it out and then Use the string to tie the caliper to the strut. Make sure that there is no tension on the brake hose connected to the caliper.
NEVER PRESS DOWN ONTO THE BRAKE PEDAL WHEN THE BRAKE SYSTEM IS TAKEN APART. THE PISTON IN THE CALIPER CAN COME OUT!
Use the brake cleaner and spray clean the hanging caliper first. Use the other old towel to cover up the rotor and torque plate from dirt that will drip down from the caliper. You might have to use the wire brush to remove brake dust buildup on the caliper. Make sure that everything is clean. Now clean around the rotor and remove the other brake pad. A nice thing is to compare the old and new brake pads side by side to see the difference between new and worn. The inside pad has a sensor wire. It is basically a wire built into the pads in a U shape that has a small amount of electrical current flowing through it. Over time, the brake pads are worn down and the sensor gets exposed to the rotors and will cause a short in the system that will cause your brake pads warning light to come on. An indication that your brake pads are worn out and its time for a change.
You still need to push the piston back into the calipers cylinder. You can either buy or rent a brake piston tool or use a clamp and the old brake pad to do the same job. When using the c clamp, put the old brake pad back into the caliper, attach the clamp to the friction side of the pad and the back side of the caliper, and slowly screw the clamp together to push the piston back.
Find your anti-squeaking compound and use it on the back side of the new pads. The compound will act as a noise reducer between the metal parts so you don't have to hear a squeaking sound every time you try to decelerate. The anti-squeaking compound is a really thick gel; so keep some tissues close by to wipe off your hands. Apply it to the following parts: rear side of the brake pads including the claw, the caliper holding clamps and the brake piston. Now reassemble the brake system by placing the pad without the sensor wire into the torque plate on the rotor. The inner brake pad is easily identified by the jaw that is behind it. That jaw will make sure that the pad stays in the caliper's piston. Push the inner pad with the jaw into the caliper housing and cut down the caliper from the strut. Keep the string for the other side.
In the end comes the tricky part. It is to get the caliper to fit right over the torque plate without having the other pad twisting around. Use a short piece of cardboard between the rotor and the pad and then pull it out just prior to setting down the caliper onto the housing. It will make the job much easier. Now use two new bolts to secure the caliper onto the rotor. If the new brake pads came with a sensor wire, then slide the new connector into the strut groove and connect the cables together. Don't forget the rubber plugs that were protecting the bolts. Make sure they have a tight seal. In case the new pads don't have a sensor wire cut the old wire off the old pad and connect the two wires to make a closed connection so it wont trigger your warning system in any way. Use the "W" spring to secure the caliper onto the rotor. Slide it back into the place with the flat head screwdriver. Attach the wheel and lower the car to the ground and repeat the procedure with the other side.
Let us do a quick review of all the important steps:
1. Park car and secure the wheels
2. Loosen up the lug nuts before you raise the vehicle
3. Open the hood and place towel around open brake fluid reservoir
4. Raise the vehicle and support it with a jack stand
5. Remove the wheel and place it out of the way
6. Disconnect the sensor wires
7. Remove the caliper holding bolts
8. Pull caliper upwards and remove old pads
9. Secure caliper to the strut housing
10. Use anti-squeaking compound on all connecting metal parts
11. Install new brake pads and reinstall caliper
12. Connect sensor wires and install new bolts
13. Attach the wheel and lower the vehicle
14. Retighten the lug nuts
15. Do the same procedure for the other side