General information about the brake system (Mitsubishi Galant 6)

All models of cars considered in this Manual are equipped with a hydraulic brake system with vacuum booster. Disc brakes are always installed on the front wheels, and both disc and drum brakes are installed on the rear wheels.

All brake mechanisms are equipped with self-regulators. In this case, wear compensation of brake pads of disc mechanisms is carried out automatically, while special adjustment devices are installed on drum mechanisms, the activation of which occurs when the parking brake is applied.

The brake master cylinder (BMC) is mounted on the brake booster servo assembly, which is secured to the rear bulkhead of the engine compartment. On top of the cylinder is a large hydraulic fluid reservoir, equipped with a plastic cover.

The brake master cylinder has a dual design, ensuring the operation of two independent hydraulic circuits (front and rear). The fluid pressure in each circuit is pumped by an individual piston inside separate chambers of the master cylinder. Since the primary piston of the brake master cylinder is directly (via a metal rod) connected to the foot brake pedal, the movement of the latter inevitably leads to an increase in the hydraulic pressure inside the brake lines. An instant increase in pressure in the lines leads to the movement of the pistons in the calipers/wheel cylinders of the brake mechanisms, and the magnitude of the force developed by the latter increases proportionally to the increment in the area of their pistons relative to the area of the brake master cylinder pistons.



Wheel cylinders of drum brake mechanisms are equipped with two pistons, pushed out in opposite directions and providing pressure of brake shoes to the working surface of the drum. In disc mechanisms, cylinders are built into caliper assemblies and provide the ability to compress the brake disc between two friction shoes.

The brake pads/shoes, as well as the master cylinder pistons, are equipped with return springs, which ensures that the system returns to its original state when the foot brake pedal is released.

The tightness of the piston fit in the cylinders is ensured by using rubber sealing cuffs; special dust covers are provided to protect the cylinders from dirt and moisture.

Master brake cylinder

The main brake cylinders of dual-circuit brake systems use two pistons installed directly one after the other. The primary piston is directly connected to the brake pedal by means of a metal rod. The secondary piston is driven hydraulically by means of the volume of liquid enclosed between the pistons. If leaks form in front of the secondary piston, the latter moves forward until it stops against the end wall of the cylinder and the liquid located between the pistons enters only the rear brake circuit of the system. If leaks occur in the rear circuit, the primary piston rests directly against the end of the secondary, ensuring the isolation of the defective section of the tract.

Hydraulic tract

All dual braking systems have the ability to warn the driver about the failure of one of the hydraulic circuits. The switch-sensor is usually built into the valve body, installed on the rear bulkhead of the engine compartment, or on the frame under the master cylinder assembly. The valve contains a piston, simultaneously connected to both circuits of the hydraulic tract in such a way that the pressure developed in them is applied to the corresponding side of the piston. If the circuits are in good condition, the pressure in both circuits is equal and the piston remains stationary. Any imbalance leads to displacement of the piston and closure of the switch-sensor, the circuit of which includes a special control lamp installed on the instrument panel of the car. In addition to the switch-sensor, the valve assembly may also include a metering valve, which ensures a delay in the supply of pressure to the front circuit until the drum brakes of the rear wheels begin to operate, which prevents the car from braking with only the front wheels.



A special regulator valve allows you to control the pressure in the wheel cylinders of the rear brake mechanisms, thereby preventing premature locking of the rear wheels during sudden braking.

The proper functioning of the control lamp can be checked by pressing the foot brake pedal with the bleeding valve of one of the brake mechanisms open. If necessary, replace the lamp or check the proper functioning of the corresponding electrical wiring and perform the necessary repairs.

Vacuum booster

The special vacuum booster, which is standard on all models, uses the vacuum created in the intake manifold to improve the efficiency of the brake system's hydraulic drive. The vacuum booster servo is mounted on the rear bulkhead inside the engine compartment.

Anti-lock brake system (ABS)

ABS prevents premature locking of the vehicle's wheels during sudden braking (see Section Replacing the brake light switch sensor).

Parking brake

The parking brake cable drive is connected to the brake mechanisms of the rear wheels of the vehicle. The drive cables are connected to the actuator levers of the brake shoe assemblies.

Service

After completing any maintenance procedure involving the removal or disassembly of any component of the brake system, be sure to check the efficiency of the brake system and only after making sure that it operates properly should you begin operating the vehicle. Test driving should be performed on a clean, dry and level road surface.

Check the vehicle's braking efficiency at various speeds and different foot brake pedal pressures. The vehicle should brake evenly while maintaining directional stability. Try to avoid premature wheel locking, which can result in loss of control.



Remember that factors that affect a vehicle's braking performance include tire condition and inflation pressure, vehicle load level, and proper suspension geometry.

Precautionary measures

When servicing vehicle brake components, there are some special precautions that should be taken:

• a) Use only DOT 3 grade hydraulic fluid to fill the brake system;
• b) The friction linings of the brake pads/shoes may contain asbestos, which is harmful to health. Avoid inhaling brake dust, and do not blow it off with compressed air. Use only special cleaning agents to wipe brake components;
• c) Ensure that all required tolerances and tightening forces are observed. When servicing components, use only serviceable tools. If in doubt, seek help from specialists. Remember that proper functioning of the brakes is the key to traffic safety;
• d) At the slightest sign of malfunction of the braking system, operation of the vehicle must be suspended!