Brake Bleeding

 

Brake Wheel Cylinder

Brake bleeding must be performed whenever the brake pedal felt 'spongy' or any brake components are replaced, for example, brake shoes, brake pads, brake calliper pistons, brake wheel cylinders or every 50,000 km or 5 years or more.  Vehicles that are 5 years or more will have brake fluid heavily contaminated and the water absorbed in the brake fluid will corrode the brake wheel cylinders, the brake piston chambers etc.. Brake bleeding at the rear wheels normally will show a highly contaminated brown fluid oozing out of the brake nipple.
When the brake system is very heavily contaminated with water and rust, the brake wheel cylinder when removed with the rubber dust cover at the side pushed upward will reveal a lump of slimy mud / clay like substance. In most cases the internal wall of the cylinder is scored and rusted . A replacement will be necessary. See photo.

Pointers on brake bleeding:

1. Bleeding is most effective with the engine running as the vacuum induced brake will easily floor the brake pedal and pumping the brake is more effective, use wheel chocks to prevent the vehicle from moving while doing this. However due to CO emission and danger of the vehicle accidentally moving off , some may prefer to do bleeding with the engine off which is also possible albeit a little harder. 
2. 
   For one-man bleeding, a long transparent vinyl tube that loops upwards from the brake nipple or better still  if the tube with its container is resting on a platform above the brake nipple, is very effective in ensuring that air will not be sucked into the system when the bleed nipple is  opened.
3. Pump the brake pedal >5 times before holding it in the pressed position.
4. Insert the Jack Trolley lever  (1/2 its length) in between the Driver's seat and the Brake Pedal to hold  down the brake pedal so that you could then open the brake nipple to release any trapped air in the system. Do not place the trolley lever in between the steering wheel and brake pedal because the steering wheel can turn and causes the lever to drop abruptly. Moreover, you can use the Driver Seat Adjuster to move so you can adjust it to the various positions required during the pump-pressed-bleed process.
5. Always check the Brake Fluid level after three to four purges (from full) to prevent the Brake Reservoir becoming empty and ingress of air into the system.