TM 5-3805-258-24-1A I R S Y S T E M A N D B R A K E SH Y D R A U L I C C I R C U I T F O R T H EW H E E L B R A K ESBRAKE FLUID RESERVOIRSReservoirs (1) and (2) are under a tool box at therear of the cab, and are the brake fluid supply forthe hydraulic circuit of the wheel brakes. Any extrabrake fluid needed to activate the wheel brakescomes from the reservoirs.Reservoir (1) provides brake fluid for the rearbrakes and reservoir (2) provides brake fluid forthe front brakes. When the brakes are released,the pressure in the lines is released to the reservoirs.L O C A T I O N O F B R A K E F L U I D R E S E R V O I R S1. Reservoir for rear wheel brakes. 2. Reservoir for frontwheel brakes.MASTER CYLINDERSR E A R O F C A BS Y S T E M S O P E R A T I O NThe two master cylinders are part of the air/hydraulic cylinders. Master cylinders (2) and (4)are under the tool box at the rear of the cab.Each master cylinder sends brake fluid to thewheel brakes on one axle. The brake fluid pressurein the master cylinder is 16 times the amount ofair pressure in the air cylinder. Master cylinder (2)sends brake fluid to the rear axle and master cyl-inder (4) sends brake fluid to the front axle.OperationAir pressure from the air circuit for the wheelbrakes goes through air inlet (11) and moves piston(12) and rod (13) to the right. Rod (13) pushes onvalve (9) and valve insert (15). Valve insert (15)closes make-up fluid inlet (8). More movement ofrod (13) pushes power piston (14). The power pistonpushes brake fluid in cylinder (17) through fluidoutlet (18) and through the lines to the wheel cyl-inders. This activates (engages) the wheel brakes.When the air pressure decreases at air inlet (11),spring (7) in air cylinder (6) moves rod (13) andpiston (12) to the left. This also causes power piston(14) to move the the left. Make-up fluid from brakefluid reservoirs is at the left side of power piston(14). When the brakes are released, rod (13) andpiston (12) go back (return) to their original posi-tions. At this time, if make-up fluid is needed incylinder (17) it comes through make-up fluid inlet(8). This make-up fluid goes around the flat sidesof valve (9) and around valve insert (15), throughpassage (16) in power piston (14) into cylinder (17).The operation of valve (9) and valve insert (15)does not permit the hydraulic circuit to have avacuum.Bleeder screw (10) is used to remove any airinside the master cylinder [cylinder (17)].1. Air cylinder for rear wheel brakes. 2. Master cylinderf o r r e a r w h e e l b r a k e s . 3 . A i r c y l i n d e r f o r f r o n t w h e e lb r a k e s . 4 . M a s t e r c y l i n d e r f o r f r o n t w h e e l b r a k e s . 5 .Brake fluid pressure (overstroke) switches.3-86
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