Bleeding Operation
When air is trapped into the hydraulic brake system, brake will be in effective. The procedure of removing air from hydraulic brake system is called bleeding of hydraulic brake.
Bleeding of Hydraulic brake systems Materials and instruments required
1. Glass jar, fresh hydraulic fluid, flexible plastic pipe of 12 meter length which can be fixed to the bleeding nipple.
2. Double end set spanner of size 10mm dry cotton waste.
Important points
1. If the bleeding nipple is provided with the master cylinder that should be bled first before bleeding before proceeding to bleed other wheels.
2. The sequences of bleeding points for right hand drive vehicle is as follows:
(a) Master Cylinder (if bleeding nipple provided)
(b) Left rear wheel
(c) Right rear wheel
(d) Left front wheel
(e) Right front wheel
(i.e, the farthest wheel from the master cylinder to be bled, after cylinder bleeding and nearest to be bled at last)
Procedure of bleeding
(i) Park the vehicle on hard level ground put the hand brake (parking brake) on.
(ii) Start the engine and run it for some line to build up the air pressure if the hydraulic brake system is assisted by compressed air (air assisted hydraulic).
(iii) Let one person sit on the driver's seat to operate brake paddle and let other person carry out the bleeding operation of different points one by one according to the sequence of mentioned above.
(iv) Connect the flexible pipe of the bleeding nipple and other end of the pipe should be placed in glass jar to preserve the bled fluid while bleeding air from the system.
(v) Ask the person who is sitting on the driver's seat to pump the brakes paddle numbers of times till it becomes hard to press but the brakes paddle to be kept in presses condition.
(vi) Loosen the bleeding screw and you will be find air bubbles coming out through bleeding nipple.
(vii) Number of times same procedure may be repeated till fresh flow of fluid at a pressure coming through the nipple.
(viii) During every repetition the bleeding nipple should be closed and opened when the signal comes from the driver that he pumped and pressed.
(ix) After every operation of bleeding check the level of brake fluid in the master cylinder.
(x) Run the vehicle and check the braking efficiency.
