Is it best to replace the rear brake assembly -pads,rotors,calipers all at the sane time ?

did you turn the rotors some times there ia ridge on the rotors that needs to be machined down.

Here ya go! This is for the rear brake pads removal:

Removal & Installation

1. Remove the brake master cylinder filler cap. Check brake fluid level in brake master cylinder reservoir. Remove fluid until brake master cylinder reservoir is half full.
   
2. Raise and support the vehicle.
   
3. Remove the wheel and tire assembly.
   
4. Inspect the brake pads for wear or contamination. If worn, damaged or past specification, install new components.
   
5. Remove the caliper pin bolts.
   
6. Remove the rear disc brake caliper.
   
7. Remove the brake pads and rail clips.
   
8. Inspect the disc brake caliper for leaks. If leaks are found, disassembly is required.
   
9. Installation is the reverse of removal. Observe the following torques:
   
   • Caliper bolts: 27 ft. lbs. (36 Nm)
     
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Brake Pads Removal & Installation Front

To Remove:

1. Drain brake fluid to ½ full level in reservoir.
2. Remove the front wheels.
   
   
3. Remove the front brake caliper assembly.
4. Remove the 2 anti-squeal shims from each of the 2 brake pads.
5. Remove the wear indicator from each of the 2 brake pads.

To Install:
NOTE: When replacing worn pads, the anti-squeal shims must be replaced together with the pads.

1. Using a large C clamp or equivalent press piston into the caliper.
2. Apply disc brake grease to the inside of each anti-squeal shim.
3. Install the anti-squeal shims on each pad.
4. Install the pad wear indicator clip to the pads.
5. Install the pads with the pad wear indicator plate facing upward.
6. Install the brake caliper with the 2 mounting bolts. Torque the bolts 25 ft-lb (34 Nm).
7. Install the front wheels.
8. Fill the master cylinder with new clean brake fluid.
9. Pump the brake pedal several times to seat the brake pads.

Rear TMC made rear brake components

TMMK made rear brake components

To Remove:

1. Drain the brake fluid to ½ full level in reservoir.
2. Remove the rear wheels.
3. Remove the caliper slide pins.
4. Remove the caliper slide pin bushings (TMMK made) (Kentucky).
5. Remove the rear brake calipers.
6. Remove the 2 brake pads with the anti-squeal shims.
7. Remove the anti-squeal shims and pad wear indicators from brake pads.

To Install:

1. Using a large C clamp or equivalent press the piston into the caliper.
2. Coat both sides of the outer anti-squeal shim with pad grease.
3. Install anti-squeal shims to each pad.
4. Install wear indicators on the 2 brake pads.
5. Install the caliper slide pin bushings (TMMK made) (Kentucky).
6. Install the rear brake caliper with the slide pins. Torque the slide pins as follows:
   • TMC made (Japan): Torque the caliper slide pin 25 ft-lb (34.3 Nm)
   • TMMK made (Kentucky): Torque the caliper slide pin 34 ft-lb (47 Nm)
7. Fill the master cylinder with new clean brake fluid.
8. Pump the brake pedal several times to seat the brake pads.
9. Install the rear wheels.

Brake Rotor Removal & Installation Front To Remove:

1. Remove the front wheels.
2. Remove the front brake caliper assembly.
3. Remove the front brake pads.
4. Remove the 2 bolts and caliper mounting bracket.
5. Place match marks on the disc and axle hub.
6. Remove the front wheel disc.

To Install:

1. Align the match marks and install the front disc.
2. Install the brake caliper mounting bracket. Torque the bolts 79 ft-lb (107 Nm).
3. Install the brake caliper. Torque the bolts 25 ft-lb (34 Nm).
4. Install new gaskets and connect the brake hose to the caliper with the banjo fitting bolt. Torque the fitting bolt 22 ft-lb (29.4 Nm).
5. Fill the reservoir with brake fluid.
6. Bleed the brake system.
7. Install the front wheel.

Rear To Remove:

1. Remove the rear wheels.
2. Remove the brake caliper assembly.
3. Remove the brake pads.
4. Remove the 2 bolts and the caliper mounting bracket.
5. Place match marks on the disc and axle hub.
6. Remove the rear disc.

To Install:

1. Align the match marks and install the rear disc.
2. Install the rear brake caliper mounting bracket. Torque the bracket bolts as follows:
   • TMC made (Japan): Torque the bracket bolt 46 ft-lb (61.8 Nm)
   • TMMK made (Kentucky): Torque the bracket bolt 34 ft-lb (47 Nm)
3. Install the rear brake caliper with the slide pins. Torque the slide pins as follows:
   • TMC made (Japan): Torque the caliper slide pin 25 ft-lb (34.3 Nm)
   • TMMK made (Kentucky): Torque the caliper slide pin 32 ft-lb (43 Nm)
4. Install new gaskets and connect the brake hose to the caliper with the banjo fitting bolt. Torque the fitting bolt 22 ft-lb (29.4 Nm).
5. Fill the reservoir with brake fluid.
6. Bleed the brake system.
7. Install the rear wheel

Those are special calipers. The piston cannot be just compressed back into the caliper - it needs to be turned as it is compressed or you can ruin the caliper.There is a kit you can rent from AutoZone or many independent auto parts stores that will perform both functions at the same time.
Block fron wheels and raise vehicle passenger side. Remove wheel. The caliper is on the top rear side of the assembly you're looking at.There are 2 long bolts you'll need to remove to take the caliper off the vehicle. Don't remove the brake line or open the bleeder screw ( either of these moves will add to your work!! ) Insert a large flat blade screwdriver in between the rotor and outboard brake pad and pry away from the vehicle slightly to release the pads from the rotor. Slide caliper upwards and towards the back of the vehicle to separate from rotor. The pads will come in a full set ( all 4 pads for both side of the rear ) . Look at your replacement pads and determine if they have a retainer clip holding them in place or a compression clip. Remove outboard pad first then inboard. Match old pads to replacement pads. Inspect rotor for grooves and irregular surfaces - if any grooves or irregularity present, remove rotor and take to an auto parts store for refinishing.Compress caliper piston with kit and allow 5 minutes for pressure to bleed back into the master cylinder.install rotor if removed and wipe surfaces with brake clean. Install inboard then outboard pad and place caliper on rotor, then mount to vehicle. Install wheel, repeat procedure for drivers side, then PUMP BRAKE PEDAL 5 TIMES BEFORE TRYING TO DRIVE VEHICLE to set pads on rotors.

Brake Pads
Removal & Installation
Front





3.4L front disc brake assembly









4.0L and 4.7L front disc brake assembly




To Remove:

1. Before servicing the vehicle, refer to the precautions in the beginning of
   this section.
   
2. Remove or disconnect the following:
   
   
   
   • Front wheel
     
   • Clip, 2 caliper pins, the anti-rattle spring then remove the 2 brake pads
     and the 4 anti-squeal shims

To Install:

CAUTION
Only replace brake pads on 1 side of the
vehicle at a time. Failure to use this procedure could cause the caliper pistons
on the opposite side of the vehicle to pop out requiring the reconditioning or
replacement of the brake caliper.

1. Remove a small amount of brake fluid from the master cylinder.
   
2. Install a used brake pad into the caliper and compress the caliper pistons.
   
3. Apply disc brake grease to both sides of the inner anti-squeal shims.
   
4. Install or connect the following:
   
   
   
   • Anti-squeal shims to the new brake pads
     NOTE: When replacing worn pads, the anti-squeal shims must be replaced
     together with the pads.
     
     
   • 2 brake pads
     
   • Anti-rattle spring and the 2 caliper pins
     
   • Clip
     
   • Front wheel
   
   
5. Depress the brake pedal several times to seat the brake pads.
   
6. Check the brake fluid level and top off as needed.

Rear
To Remove:

1. Before servicing the vehicle, refer to the precautions in the beginning of
   this section.
   
2. Remove or disconnect the following:
   
   
   
   • Rear wheel
     
     
     
     
     
     
     
     
     
     
     
   • 2 cylinder slide pins from rear caliper assembly
     
   • Caliper assembly from rear caliper mounting
     
   • 2 brake pads with anti-squeal shims from rear caliper mounting
     
   • 2 anti-squeal shims from each disc brake pads
     
   • Pad wear indicator plate from the inner side disc brake pad
     
   • 4 pad support plates from the rear caliper mounting

To Install:

1. Install or connect the following:
   
   
   
   • 4 pad support plates on the rear caliper mounting
     
   • Pad wear indicator plate on the inside brake pad
     Note: Install the pad wear indicator facing downward.
     
     
   • Anti-squeal shims on each brake pad
     
   • 2 disc brake pads with anti-squeal shims to the caliper assembly
   
   
2. Apply lithium soap base glycol grease to the sliding part of 2 caliper slide
   pins.
   
3. Install or connect the following:
   
   
   
   • Disc brake caliper assembly with 2 caliper slide pins
     
   • Torque to 65 ft-lbs (88 Nm)
     
   • Rear wheel
   
   
4. Depress the brake pedal several times to seat the brake pads.
   
5. Check the brake fluid level and top off as needed.

--- Removal & Installation
Front
To Remove:

1. Before servicing the vehicle, refer to the precautions in the beginning of
   this section.
   
2. Remove or disconnect the following:
   
   
   
   • Front wheel
     
   • Front brake caliper assembly
   
   
3. Make matchmarks on the disc and the axle hub.
   
4. Remove the front disc.

To Install:

1. Align matchmarks and disc onto axle hub.
   
2. Install or connect the following:
   
   
   
   • Front brake caliper assembly with the 2 bolts
     
     
     
     1. Torque to 90 ft-lbs (123 Nm)
     
     
   • Front wheel

Removal & Installation Front To Remove:

1. Inspect the fluid level in the master cylinder reservoir. Remove fluid from the reservoir until the level is lower then half way between the MAX and MIN levels.
2. Remove the tire and wheel assembly.
3. Install 2 wheel nuts to secure the rotor on the hub.
4. Remove the bottom brake caliper pin bolt.
5. Pivot the brake caliper body upward and secure out of the way. Do NOT disconnect the hydraulic brake flexible hose from the caliper.
6. Compress the piston back into the bore using a C-clamp. Figure of brake assembly with caliper raised showing brake pads in mounting bracket
   
   
7. Remove the inboard and outboard brake pads from the brake caliper bracket.

To Install:

1. Install the brake pad retainers and both brake pads into the caliper bracket.
2. Pivot the brake caliper down over the brake pads and into the brake caliper bracket. Insert the lower brake caliper pin bolt and torque bolt to 70 ft-lb. (95 Nm).
3. Reinstall the tire and wheel assembly.
4. Lower the vehicle.
5. Refill the master cylinder. Pump the brake pedal several times to seat the pads against the rotor.
6. Check the master cylinder level and add fluid as necessary.

Rear To Remove:
Rear disc pads R&I

1. Inspect the fluid level in the master cylinder reservoir. Remove fluid from the reservoir until the level is lower then half way between the MAX and MIN levels.
2. Remove the tire and wheel assembly.
3. Install 2 wheel nuts to secure the rotor on the hub.
4. Remove the upper caliper mounting bolt.
5. Pivot the caliper down to access the pads.
6. Remove the inboard and outboard pads from the caliper bracket.
7. Remove the brake pad clips from the caliper bracket.
8. Compress the piston back into the bore using a C-clamp and the old inner pad.

To Install:

1. Install new brake clips in the caliper bracket.
2. Install the inboard and outboard pads in the caliper bracket.
3. Pivot the caliper up over the pads.
4. Reinstall the upper mounting bolt and tighten to 32 ft. lbs. (44 Nm).
5. Remove the 2 wheel nuts securing the rotor.
6. Reinstall the tire and wheel assembly.
7. Refill the master cylinder. Pump the brake pedal several times to seat the pads against the rotor.
8. Check the master cylinder level and add fluid as necessary.

you have to loosen the emergency brake adjustment on the cable give it some slack push the shoes together by hand and rotor will fit . please dont forget to rate this answer . hope this helps

Rear disc brake pads offer better performance and are not as affected by moisture like conventional brake shoe style brakes are. Rear disc brakes are similar to front disc brakes. The main difference is that rear disc brake systems must incorporate the emergency brake system. There are two methods widely used for the emergency brake with rear disc systems. The first system is a brake shoe inside the brake disc that is actuated by the emergency brake lever. The second is a screw style actuator inside the brake caliper. When activated the brake pads are forced into the brake disc and held tightly by the emergency brake lever.
READ COMPLETELY BEFORE STARTING
Step 1 - Identify Rear Disc Brake Components
Rear disc brake assembly includes; rear brake disc, rear brake pads, brake caliper mount and a caliper mounting screw. (Note: Some vehicles do not have the rotor mounting screw.)
Step 2 - Removing the Rear Brake Caliper Mount Bolts
To replace rear brake pads and rotors the rear brake caliper needs to be removed. First loosen the rear brake caliper mount bolts and remove them. Turn counter clockwise.
Step 3 - Lift Rear Brake Caliper from The Caliper Mount
After the caliper mount bolts have been removed, gently lift the brake caliper from the caliper mount. Inspect the caliper slides; they should move freely in the caliper mount. Remove rear brake pads and hardware.

Step 4 - Removing Caliper Mount Bolts
With a socket wrench or other appropriate removal tool, loosen the rear brake caliper mounting bolts. Remove bolts and lift the caliper mount and remove it from the vehicle. Remove the retaining screw from the disc mounting hole. Tap the rotor gently to release any rust that has accumulated between the rotor and bearing hub. Lift brake rotor from wheel hub holding on tightly, using both hands. You do not want to drop the rotor.

Step 5 - Removing Rear Brake Rotor
Remove the retaining screw from the disc mounting hole, tap the rotor gently to release any rust that has accumulated between the rotor and bearing hub. Lift brake rotor from wheel hub, hold on using both hands and do not drop.

Step 6 - Install New Brake Rotor
Check the new rotor against the old brake rotor to make sure they are the same size. Clean the mating surface on the wheel hub before the new brake rotor is installed. Reinstall rotor retainer screw.
Step 7 - Reset Rear Brake Caliper
Before new brake pads can be installed, the rear brake caliper must be reset. The reset tool winds the piston back into position so the new brake pads will fit. This style of brake caliper will not compress with a clamp tool; it can only be reset with the proper reset tool.
Step 8 - Reinstall Rear Caliper Mount and Install New Rear Brake Pads
After the caliper has been reset, reinstall caliper mounting bolts and make sure the bolts are tight. Then match up the old brake pads to the new brake pads. They should be exactly the same except, of course; the old ones will be worn out. Check the new brake pads for proper fit and install any brake hardware that is required.
Step 9 - Remount Rear Brake Caliper
Reinstall the brake caliper, align brake pad hardware and reinstall caliper mounting bolts. (Note: align the rear peg of the brake pad to the groove in the caliper piston.) Recheck and retighten all caliper and caliper mount bolts. Bleed brake system to relieve any air in the system. Before driving the vehicle, push the brake pedal down and let it up slowly. This operation forces the brake pads to travel to the brake rotors. DO NOT DRIVE VEHICLE until proper brake pedal operation resumes. When test driving vehicle listen for any unusual noises during the operation of the brakes.
WARNING! Always have the vehicle under inspection on level ground, in park with the emergency brake on. Always wear protective eyewear, gloves and necessary clothing before inspection or work begins. Never crank an engine over when anyone is near the battery or engine. Always have an operational fire extinguisher close by, obey all first aid instructions in the event of an injury. Never stand in front or behind a vehicle when cranked over or running. When engine is cranked over keep hands and clothing away from rotating components. Never move a car without proper brake pedal operation.

find out what tool you need to remove bolts for the caliper(2) once you get the bolts out remove caliper. next step remove old pads.then you will need a c clamp to compress piston on the caliper back in then get new pads and install them on caliper easy fix reinstall caliper on to rotor and put bolts back in just observe how the caliper came off

So this is what it takes to replace rear brake rotors on a 2003 Mercedes E320;
1) open the bonnet (hood) of the car and loosen/remove the cap off of the brake fluid resevior.
2) remove outer spring clamp from brake assembly (it clips in to the iner edge of the holes of the caliper).
3)using a 7 MM allen wrench, remove the brake caliper.
4) using 18 MM box wrench, remove the caliper housing assembly off of the wheel hub.
5) using a star wrench, unscrew the rotor locking screw from the rotor
6) squirt some liquid wrench on the rotor hub and knock the rotor with a hammer to work the liquid wrench in.
7) using the same hammer, knock the rotor off the hub.
8) using a metal file, lightly file old residue off of the hub and place the new rotor on the hub.
9) set the hub by screwing in the lug nuts and then screw in the hub locking screw using the star wrench, then remove the lug nuts.
10) reinstall the caliper housing assembly onto the wheel hub using the 18 MM box wrench.
11) push back the brake claiper piston to its home position and install the inner brake pad (the one with the snap clips)
12) insert the outer brake pad in the claper housing assembly.
13) slide on the caliper housing with the inner brake pad in place (over the outer brake pad) and screw in the caliper screw rods using the 7 MM allen wrench
14) on the right wheel brakes, DO NOT FORGET to slide in the brake sensor (the one with the black connector) and connect it to the connector on the caliper housing.
15) be sure to reinsert the spring clamp onto the outer brake assembly to set the assembly squarely onto the wheel (there should be no wiggle in the brake assembly after the spring clamps are installed).
16) finally mount the wheels.
17) you can bleed the brakes at this point to release any trapped air (which is unlikely) but be sure to pump the brakes after starting the car BUT BEFORE MOVING IT to re-preassurize the brake system before driving the car.
17) ONE WEEK LATER - recheck brake assembly to ensure all is okay and brake fluid.

This proposed solution is for a 2003 Mercedes Benz E320 and NOT a 2005 model as stated by the limited option selection provided by FIXYA.com when initially describing the problem.