Braking is the most valuable function of the car that keeps us alive. So having it properly checked is always safe. Although the 120y was originally designed to have a brake pump that transfers mechanical energy from the pedal to the wheel cylinder via brake fluid with 4 drum brakes the later models had front disk brakes.
The braking system is a non-servo braking system which demands a bit of muscular strength to push the brake pedals and less ability to quickly respond but these were excellent brakes at the time the car was made.
What happens when we press the pedal down is the spring loaded pistons inside the master cylinder moves forward due to the mechanical force applied by the foot and deliver a hydraulic force through the brake line to the pistons inside the wheel cylinders moving the brake shoes toward the brake drum. The friction between the brake drum and the brake lining generates heat from the kinetic energy of the car thus reducing its speed. When we take foot off the pedal the return springs push the brake pedal back to the original position and the volume of brake fluid required to transfer the pushing force returns back to the reservoir and brake lines remain filled ready to be applied again.
Over the time the brake lining grows thin due to wear off. There is a mechanical self adjustment design which 120y lacks and has manual adjustments instead which allows the brake lining to move further forward towards the drum so that the pistons has a little distance to take the lining to the drum.
The 120y has 2 wheel cylinders per wheel which pushes one brake shoe towards the drum. The usual reasons for bad brakes are the wear off of lining, bad brake washers and worn off wheel cylinders in the case of wheels.
After properly lifting the 46 year old car to a height that its wheel can be taken off I removed the brake drum. If the drum is too tight to come out we can loosen the brake shoes from the adjustment nuts behind the wheel. When the drum is removed if the brakes has been working properly the unit should be covered in dust that came out due to wearing of brake lining.
The brake washers hold the brake fluid inside the wheel cylinder to supply the required pressure to the piston. If the washers are worn off or dried off it needs to be replaced. In that case the washers were replaced after checking the condition of wheel cylinders. Then the drum was put back in and the air inside the brake line was removed by bleeding.
A simplified drawing of front drum brakes of the car was drawn and uploaded here.
To take out the washers it was needed to take out brake shoes as they had high tension return springs it was done very carefully.
Pahan's Garage 