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This job takes about 30 minutes of actual work (once you have the car off the ground and wheels off). This is pretty easy but requires attention and a lot of soap afterwards. If you are not comfortable or competent with working on your brakes, leave it to a professional!
Click on the images for larger views. |
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Note:
- Your front wheels must be off the ground to change brake pads. See Getting car up on jack stands DIY.
- I assume that your car is already up on a lift or on jack stands and the wheels are off.
- I made a bit of a boo-boo when I took pictures for this DIY - I took the pictures on the driver's side rear which does not have a brake wear sensor. The passenger rear brake has a brake wear sensor (like the front passenger does). I do cover removing the brake wear sensor in the Front Brake Pad DIY and the steps for removing the sensor from the pad and reinstalling it into the new pad are identical. You do not have to worry about releasing the brake wear sensor wire from any brackets on the rear brake pad install like you do in the front brake version - just need to pop it out of the pad.
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Step 1: Getting the required items together
This job requires:
- A lift or some other method of getting the rear wheels off the ground.
- 7mm Allen Head Socket
- Socket Wrench
- Torque wrench (recommended)
- 6" or larger "C" clamp
- Large flat screwdriver
- Small flat screwdriver
- Disk brake anti-squeal compound
- Brake cleaner
- Something to rest calipers on (Cardboard box, spare jack stand, etc - something about as tall as bottom of the caliper).
- A BMW M3 (E46).
- About 30 minutes of free time.
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M3 Rear Disk Brake |
Step 2: Start on Driver's Side by Removing the Brake Pad Anti-Rattle Clip
- Use your flat head screwdriver to pry under one of the arms of the clip and to push the arm away from the rotor toward yourself (see image).
- This can take a little doing and may require a little imagination (some claim this can be done with your hands - I like my fingers in one piece).
- When the clip releases it may pop off with a little zest do watch your face, etc. and don't get blinded by a flying anti-rattle clip.
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Anti-Rattle Clip
Prying the Clip Off |
Step 3: Removing Plastic Bolt Caps
- A short and simple step - there are two plastic caps that protect the bolts used to retain the calipers.
- These are located on the back side of the caliper (see image) - just pull them out with your fingers.
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Plastic Caps
7mm Retaining Bolts Exposed |
Step 4: Giving Things a Squeeze (Compressing the Piston)
- You need to compress the brake piston. This can be done on the car (easier) or once the caliper is off the car (harder).
- There is a special tool to do this via BMW but since you don't have one (I'm willing to bet on that) we will use our own special tool - a garden variety 6" or larger "C" clamp.
- Open the clamp and place the end on the back of the brake piston housing (see second image).
- Place the other end on the outside brake pad (see first image).
- Gently compress till you meet resistance. Depending on the condition of you brake pads you will see the outside brake pad move in about a 1/4" from its starting position.
- CAUTION: Watch brake fluid level in the brake fluid reservoir as you compress the piston. You're compressing the system with the clamp and forcing fluid out of the caliper - make sure the fluid reservoir does not over flow - there is nothing worse than brake fluid for paint - if the reservoir gets close to overflowing, use a turkey baster, etc. to siphon off a little fluid. Do not siphon off any more than required to keep it from overflowing. Make sure to replace what ever fluid you siphon off with NEW fluid after you're done.
- Remove the clamp.
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Clamp Location From Front
Clamp Location From Back
Clamp Location From Rear
Brake Fluid Reservoir |
Step 5: Preparing to Remove the Caliper
- You will need something to set the caliper on after its released or it will hang down by the brake line - not the world's brightest idea. A cardboard box about the same height as the caliper works well.
- Using the 7mm Allen bit, loosen the two caliper retaining bolts. These are both accessed from the back of the caliper (these are the bolts that were covered by the plastic caps you removed in Step 3).
- You don't have to pull these all the way out but its probably easier just to do so.
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All the Stuff Taken Off So Far |
Step 6: Removing the Caliper
- Carefully pull the caliper directly back toward the back of the car - mind the fact that the brake line are still attached to the unit!
- Once released, set the caliper on what ever you are using for a support.
- Your outside brake pad will stay on the brake pad carrier, just lift it out and set it aside (don't toss it yet!).
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Removed Caliper |
Step 7: Releasing the Inboard Pad
- The inboard brake pad is clipped into the piston (see image).
- Gently push the pad toward the center of the caliper to release - keep in mind that if you are working on the passenger rear brake the wear sensor wire will still be attached. On the passenger side, simply use a small screwdriver to pop the brake wear sensor up and out of the recess in the top edge of the inboard brake pad. If you need pictures to figure this out - look in the Front Brake Pad DIY.
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Step 8: Cleaning Up
- Use brake cleaner to thoroughly clean both the runners on brake pad retaining bracket and the caliper (particularly the piston and the outboard arms).
- Wipe clean.
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Brake Pad Carrier Bracket
Caliper |
Step 9: Preparing the New Pads for Installation
- Examine your old pads and note the areas of the pad that contact the piston and the caliper.
- Apply a liberal amount of anti-squeal compound to the new pads in the area where they will contact the caliper and piston (use the old pads as a template).
- Too much is better than too little here and this is a place where its OK to be messy.
- Don't worry about being able to see the anti-squeal compound once the brakes are installed - after a couple of days, whatever color the compound you used will be turned into a nice shade of brake pad dust gray.
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Brake Pads
Old Pads, left
New Pads, right |
Step 10: Installing the Inboard Brake Pad
- Set the new, anti-squeal coated inboard brake pad into the piston inside the caliper (see image).
- The clip on the back of the inboard pad will snap into the piston itself and snap in securely.
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New Inboard Pad in Caliper |
Step 11: Installing the Outboard Brake Pad
- Set the new, anti-squeal coated outboard brake pad into the brake pad carrier (see image).
- The pad will just loosely sit in place until the caliper is installed.
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New Outboard Pad in Carrier |
Step 12: Installing the Caliper
- Slide the caliper back on making sure that the outboard pad stays on the brake pad carrier.
- Reinstall the two retaining blots to hold the caliper in place and torque them down to 22 ft lbs.
- Reinstall the two plastic caps you removed in Step 3. (they just pop back in by hand)
- If you're working on the passenger side rear brake you will need to pop the brake wear sensor back in place. You will be able to see the recess in the inboard pad through the back of the caliper. Gently snap the sensor back in and check to make sure its seated. If you need pictures, refer to the Front Brake Pads DIY.
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Caliper In Place |
Step 13: Reinstall the Anti-Rattle Clip
- The anti-rattle clip just snaps back on the caliper.
- Slide the clip in from the front of the caliper until it snaps back into place.
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Anti-Rattle Clip In Place |
Step 14: Finishing Up
- Reinstall the wheel and torque the lugs to 88 ft lbs.
- Repeat for passenger side - As noted in many of the steps above the passenger side rear brake has a wear sensor - The additional steps to remove the brake wear sensor are annotated where relevant. You cna also look at the Front Brkae Pad DIY for pictures of the process (though only poping hte sensor out of the pad is relevant - you do not need to release the wear sensor wire from any brackets when working on rear brakes).
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