🔧 GLA - Rear Brake Pads & Rotor Replacement

You’ll remove the rear wheels, swap the rear brake pads and rotors, then compress the rear caliper pistons and reassemble everything with correct torque. This restores braking performance and prevents vibration/noise from worn pads or warped rotors.

Difficulty Level: Intermediate | Estimated Time: 2-4 hours

Assumption: Providing both rear parking-brake variants used on the GLA (EPB-on-caliper vs drum-in-hat).

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⚠️ Safety & Precautions

• ⚠️ Support the A4—use jack stands; never rely on a jack.
• ⚠️ Let brakes cool fully; hot rotors can burn you.
• ⚠️ Do not press the brake pedal with a caliper removed.
• ⚠️ If equipped with an electronic parking brake (EPB), retract it before pushing pistons in, or you can damage the EPB motor.
• ⚠️ Brake dust is harmful—use brake cleaner, not compressed air.
• ⚠️ Battery disconnect is not required for this job.

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🔧 Required Tools

You'll need the following tools for this repair:

• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• 17mm socket
• 3/8" drive ratchet
• 1/2" drive breaker bar
• Torque wrench (20-200 Nm range)
• 7mm hex bit socket
• E18 external Torx socket
• Torx T30 bit
• Flat-blade screwdriver
• Brake caliper piston compression tool (specialty)
• OBD scan tool with Mercedes EPB service function (specialty)
• Bungee cord or caliper hanger hook
• Wire brush
• Brake cleaner spray
• Shop towels
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Rear brake pad set - Qty: 1
• Rear brake rotors - Replace in pairs - Qty: 2
• Rear brake pad wear sensor - Qty: 1
• Brake grease (silicone or ceramic) - Qty: 1
• Threadlocker (medium strength) - Qty: 1
• Anti-seize compound - Qty: 1

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📋 Before You Begin

• Park on level ground, set the transmission to Park, and chock the front wheels.
• Release the parking brake fully before lifting.
• Open the hood and check the brake fluid reservoir level; it may rise when you compress pistons.
• If equipped with EPB: put the EPB into service mode before touching the rear calipers.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Loosen rear wheel bolts

• Use a 17mm socket and breaker bar to loosen the rear wheel bolts about 1/2 turn while the vehicle is on the ground.

Step 2: Lift and support the rear

• Use a floor jack to lift the rear at the approved jacking point.
• Place jack stands securely and lower the vehicle onto them.
• Remove the wheels using a 17mm socket.

Step 3: Identify which parking brake system you have

• Look at the back of the rear caliper.
• If you see an electric motor/connector on the caliper, you have EPB-on-caliper.
• If there is no motor and the rotor “hat” area is large, you likely have a drum-in-hat parking brake inside the rotor.

Step 4A: Retract EPB (EPB-on-caliper only)

• Connect your OBD scan tool with Mercedes EPB service function (specialty).
• Command the parking brake to Workshop/Service mode (wording varies by scan tool).
• This backs the motor off safely.

Step 4B: Ensure parking brake is released (drum-in-hat only)

• Make sure the parking brake is fully released before removing the rotor.
• If the rotor is stuck later, you may need to back off the shoe adjuster through the access hole (shown in Step 8B).

Step 5: Remove the rear caliper

• Turn the steering is not required—rear is straight—just access the caliper bolts from behind.
• Remove the two caliper guide pin bolts using a 7mm hex bit socket and ratchet.
• Lift the caliper off the bracket and hang it using a bungee cord or caliper hanger hook.
• Never let the caliper hang by the hose.

Step 6: Remove pads and inspect hardware

• Remove the old pads by hand; use a flat-blade screwdriver gently if they’re tight.
• Unclip and remove the wear sensor (if installed) using a flat-blade screwdriver.
• Inspect pad abutment clips and the caliper slide pins for rust or sticking.

Step 7: Remove the caliper carrier (bracket)

• Remove the carrier-to-knuckle bolts using an E18 external Torx socket and breaker bar.
• Torque to 115 Nm (85 ft-lbs) on installation (use torque wrench).

Step 8: Remove the rotor

• Remove the rotor retaining screw using a Torx T30 bit and ratchet.
• Pull the rotor straight off the hub.

Step 8B: If rotor won’t come off (drum-in-hat only)

• Find the rubber access plug in the rotor hat (or align the access hole) and remove it using a flat-blade screwdriver.
• Use a flat-blade screwdriver to turn the star wheel adjuster to loosen the parking brake shoes until the rotor frees up.

Step 9: Clean the hub and install the new rotor

• Clean the hub face using a wire brush and brake cleaner spray.
• Apply a very thin film of anti-seize compound to the hub face (keep it off rotor friction surfaces).
• Install the new rotor and reinstall the retaining screw using a Torx T30 bit.
• Torque to 10 Nm (7 ft-lbs) for the rotor retaining screw.

Step 10: Reinstall the caliper carrier

• Position the carrier and start bolts by hand.
• Use an E18 external Torx socket to tighten, then use a torque wrench.
• Torque to 115 Nm (85 ft-lbs).
• Apply threadlocker (medium strength) to clean carrier bolt threads.

Step 11: Compress the rear caliper piston

• Place an old pad against the piston face.
• Use a brake caliper piston compression tool (specialty) to slowly push the piston back into the caliper.
• A piston compression tool is a screw-type press that pushes the piston in evenly and safely.
• Watch the brake fluid reservoir so it does not overflow; remove a little fluid if needed using shop towels.

Step 12: Install new pads and wear sensor

• Apply a light coat of brake grease to pad ears/backing plates where they contact the bracket (do not get grease on pad friction material).
• Install the new pads into the carrier.
• Install the new wear sensor on the correct pad position and route the wire in the factory clips.

Step 13: Reinstall the caliper

• Set the caliper over the new pads.
• Install the guide pin bolts using a 7mm hex bit socket and ratchet, then tighten with a torque wrench.
• Torque to 30 Nm (22 ft-lbs) for the guide pin bolts.

Step 14: Repeat on the other rear side

• Repeat Steps 5 through 13 on the other rear wheel.
• Always replace pads/rotors in pairs.

Step 15: Reinstall wheels

• Install wheel bolts hand-tight.
• Lower the vehicle off the jack stands using the floor jack.
• Torque wheel bolts in a star pattern using a torque wrench.
• Torque to 130 Nm (96 ft-lbs) for the wheel bolts.

Step 16A: Exit EPB service mode (EPB-on-caliper only)

• Use the OBD scan tool with Mercedes EPB service function (specialty) to command EPB back to normal mode.
• Apply and release the parking brake once to confirm normal operation.

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✅ After Repair

• Pump the brake pedal 10-15 times until it feels firm before driving.
• Check brake fluid level and top up only if needed.
• Confirm there are no warning messages and the wear sensor is connected.
• Do a cautious test drive: start at low speed, confirm braking is smooth and straight.
• Pad bedding (break-in): do 6-10 moderate stops from 35 mph to 10 mph, letting brakes cool 30-60 seconds between stops.

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💰 DIY vs Shop Cost

Shop Cost: $450-$850 (parts + labor)

DIY Cost: $160-$420 (parts only)

You Save: $290-$430 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 hours.

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🎯 Ready to get started?

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