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While most new vehicles today have four disc brakes, there are still a large number of cars with rear drum brakes on the road. When the seals are worn out or if the wheel cylinders leak, their replacement must be considered.

Text and photos C. Petitjean

Practical advice

● For safety reasons, it is best to use original parts or the OE mark. Adaptation parts from unknown sources may be dangerous to use.
● Before reassembling the drum, make sure that the elements are in place and that the protective rubbers of the cylinder are not pinched. Practice a progressive braking during the first 500 km.

In the past, brake repairs were quite laborious. It was necessary to get the jaws on one side, the cylinders on the other, and have specialized tools, especially to raise the return springs. Now, there are pre-assembled brake kits including jaws, cylinders, small accessories and even a small bag of grease!

Disassemble the rear brakes

Stow the car on a flat concrete area, the rear axle lifted supported by candles. After disassembling the wheels, unscrew the rocket end nut, then pull on the drum to remove it. Dust dry with a brush, protecting yourself with a respirator.
● Remove the retaining pins from the jaw block with the pliers and unhook the handbrake control cable. Remove the hydraulic cylinder (called the wheel cylinder), after having unscrewed its supply pipe and its screw placed behind the flange.

Replacing

Reassemble the new wheel cylinder on which you will reconnect the hydraulic hose by tightening its threaded end. Apply a thin layer of special grease to the flange seats.
● The preassembled jaw kit is equipped with an automatic compensating device to compensate for the wear of the linings. Hook the end eyelet of the handbrake cable into the hook of the control lever. Place the left jaw in range on the lower stop of the flange and in the upper part on the left push of the wheel cylinder. While holding the left jaw in position, pull the right jaw to compensate for the effect of the springs and set it up as the previous one.
● Fit the two holding pins of the jaws on the flange. Each one crosses the two rooms by opposite holes. Line the pin with a coil spring, then the cup, and turn the cup a quarter of a turn to the clip while compressing the spring. Reassemble the drum, brake the rocket nut after having tightened it to the desired torque.

The purge

The goal is to chase the air contained in the pipes. Place one end of a clear plastic tube over the bleed screw and the other end into a jar containing brake fluid. Unscrew the bleed screw half a turn and have a helper operate the brake pedal several times. Close the circuit by tightening the screw after each pedal down. When no more air bubbles escape into the flowing liquid, firmly tighten the screw and repeat the operation on the other wheels. During and after bleeding, fill the tank level with the brake fluid recommended by the manufacturer, often Dot 4 or Dot 5.

Braking kit

Braking kit

The brake kit, specific to each make and type of car (see gray card), has two pairs of preassembled jaws, two wheel cylinders, hardware and even grease.

Disassemble the drum

Disassemble the drum

With the drum pulled out, take the pins out by twisting the pins a quarter of a turn. Remove the jaw block and the cylinder. Dust and degrease the flask with white spirit.

Fit the wheel cylinder

Fit the wheel cylinder

Fit the new wheel cylinder. Its shouldered base is supported in a large hole of the flange, and the fixing is provided by a screw placed behind. Reconnect the hydraulic line.

Lubricate the flange

Lubricate the flange

Use the small bag of special grease to lubricate the flange where the slices of the jaws will wear. This promotes their low mobility when working.

Engage the eyelet on the hook

Engage the eyelet on the hook

The left jaw has a lever with a hook at the bottom. The handbrake cable passes through the flange obliquely and ends with a grommet. Engage it on the hook.

Fit the right jaw

Fit the right jaw

The left jaw leans down on the fixed stop of the flange, up on the cylinder push-button. Place a grabber and pull on the right jaw to mount it like the other.

Place spring and cup

Place spring and cup

The pin being held with the finger in the back, place at the front, on its stem comprising two pins, the spring and the cup. Press the spring and turn the cup a quarter of a turn to the pliers.

Bleed the brakes

Bleed the brakes

Bleed the brakes with a commercial device or have a helper operate the pedal. Permanently block the bleed screw when a clean, bubble-free liquid flows.


Video Instruction: The ULTIMATE Guide on How to Replace Drum Brakes