BRAKE SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
PURGE BRAKE SYSTEM AIR - CONTINUED
Check oil level in hydraulic oil tank. Maintain correct oil level in hydraulic oil tank throughout air removal procedure.
Fasten one end of transparent tube 0.25 in. (6.4 mm) in diameter to one purge screw. Place other end of tube into con-
tainer for collecting hydraulic oil. Loosen purge screw.
Slowly press service brake pedal. Hold pedal in this position throughout step 4.
As hydraulic oil flows through tube, check for air bubbles in oil. Allow oil to flow into container until no air bubbles are
visible, then tighten purge screw. Release brake pedal.
Perform this procedure at each purge screw. Make sure to tighten each purge screw.
If service brake pedal is spongy, recheck oil level in hydraulic tank and repeat steps 3 thru 5.
Check hydraulic oil tank level and fill hydraulic tank if necessary.
SERVICE BRAKING SYSTEM PRESSURE TEST
Remove hydraulic oil pressure from brake system by pushing on brake pedal until there is no brake pressure.
Observe pressure before starting engine. Hydraulic oil pressure should be 0 psi (0 kPa).
Start engine. Allow hydraulic oil to reach normal operating pressure and temperature (TM 5-3805-290-10).
Press and hold brake pedal. DO NOT permit brake pedal to come up. Observe pressure. Pressure must be 810 ± 60 psi
(5,600 ± 400 kPa).
If brake pressure is not within specified range, but test for accumulator was in specified range, one of these conditions
Brake control valve is faulty.
Piston leakage is present in brake system.
Perform one of these steps to check brake pressure:
N OT E
Hydraulic oil pressure for upper brake port (rear brakes) should be approximately 250 psi (1,700 kPa)
higher than hydraulic oil pressure for lower brake port (front brakes). MSD monitors brake pressure from
rear brakes. Test port monitors pressure in front brakes.
Use MSD to monitor pressure for rear brakes.
Install new O-ring on coupling half. Install test fitting on tube T. Install T in brake line to rear axle if T is not in
line. Repeat procedure on line for rear service brakes.