Checking the tightness of the rear sealing ring
Install the master cylinder on the stand (pic. 3-10), while providing a good seal between the cylinder flange and the mating plane of the stand. Attach vessel 2 with hydraulic fluid to the cylinder. Open the compressed air cock with the adjusting screw 6 unscrewed, and then slowly turn the adjusting screw until the air comes out of the vessel 2.
Pic. 3-10. Checking the tightness of the rear sealing ring:
1 - main cylinder; 2 - vessel; 3 - adapter with seal; 4 - pressure gauge; 5 - tee; 6 - adjusting screw; A - air from the compressor; B - air outlet.
Check the air pressure on the pressure gauge, which should be in the range of 0.05-0.08 MPa (0.5-0D kgf/cm2). If the pressure is less, replace the rear O-ring.
Front O-Ring Leak Test
Install the master cylinder on the stand and connect it to a vessel filled with hydraulic fluid and to pressure gauges (pic. 3-11).
Pic. 3-11. Checking the tightness of the front sealing ring:
1 - screw for pumping; 2 - crane; 3 - pressure gauge with a division value of 0.2 MPa (2 kgf/cm2); 4 - pressure gauge with a division value of 0.005 MPa (0.05 kgf/cm2); 5 - vessel; 6 - pusher; 7 - master cylinder.
Close the valve of the pressure gauge 3 and, by moving the pusher of the main cylinder, ensure a stable pressure of 0.2 MPa (2 kgf/cm2).
With the pusher fixed and no fluid leakage, the pressure should remain constant for 2 minutes.
Close the pressure gauge valve 4 and open the pressure gauge valve 3. By moving the pusher, set a stable pressure of 10 MPa on the pressure gauge (100 kgf/cm2).
With the pusher fixed and no fluid leakage, the pressure must remain constant for at least 2 minutes. Otherwise a forward sealing ring replace.