DEMO - 1965 Ford Truck Shop Manual - ForelPublishing.com

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PART 2-4-MIDLAND DIAPHRAGM-TYPE DASH-MOUNTED BOOSTER 2-41 by additional movement of the control valve diaphragm. As the air is admitted, it flows through a cavity in the control valve housing to the back side of the rear vacuum piston, through the piston rod, out the four holes in the piston rod to the back side of the front vacuum piston. Air pressure on the back side of both pistons working with vacuum on the front side of both pistons, sets the pistons in motion transmitting their combined force to the hydraulic piston in the hydraulic cylinder, through the push rod. As the hydraulic piston starts to move, the check ball seats, trapping fluid under pressure ahead of the piston. This initial hydraulic pressure from the master cylinder is multiplied several times. When the brake pedal is released, hydraulic pressure in the master cylinder, and in the control valve piston cavity of the booster, decreases. The vacuum diaphragm return spring moves the diaphragm and the control valve piston rearward permitting spring pressure to seat the atmospheric valves, and unseat the vacuum valve. The check valve in the hydraulic cylinder closes. As the vacuum valve opens, air in the booster is exhausted into the intake manifold of the engine, allowing the vacuum piston return spring to return the vacuum and hydraulic cylinder pistons to their released position. As the hydraulic cylinder piston returns, the check ball opens permitting brake fluid to flow through the piston, allowing it to return to its fully released position. Normal operation of the booster is such that both vacuum pistons are set in motion at the same time. However, when a fast, hard brake stop is made, the front vacuum piston may lag behind the rear vacuum piston. A fast application is used to overcome the lag of the front piston by admitting an additional volume of air to the back side of the front piston. Vacuum, from the constant vacuum line, is applied to the back side of the fast application valve diaphragm. The fast application valve is held in a closed position by a spring. When a fast or hard brake stop is made, atmospheric pressure is transmitted through the control by-pass tube to the front side of the fast application valve diaphragm. This causes the diaphragm to move to the left, lifting the valve from its seat and admitting a large volume of air from the air inlet by-pass hose to the back side of the front piston, thus providing the same degree of power to both vacuum pistons. MIDLAND DIAPHRAGM- TYPE, DASH-MOUNTED BOOSTER The booster consists of a vacuum chamber, atmospheric valve, control valve plunger assembly, diaphragm and an atmospheric chamber (Figs. 8, 9, and 10). Atmospheric pressure is present at all times in the atmospheric chamber at the front side of the atmospheric valve. The air intake to the atmospheric chamber is protected by an air filter. The atmospheric chamber is separated from the vacuum chamber by the bellows assembly within the vacuum chamber. Vacuum is present at all times in that area of the vacuum chamber y MASTER CYLINDER PISTON VACUUM MANIFOLD |P|VACUUM ^ATMOSPHERIC PRESSURE FIG. HYDRAULIC CHECK VALVE VACUUM MASTER CYLINDER PUSH ROD BELLOWS 8—Booster in Applied Position ATMOSPHERIC PRESSURE RESERVOIR FILTER FIG. 9-Booster in Holding Position forward of the diaphragm. Vacuum is supplied through a hose from the intake manifold to the vacuum manifold and check valve assembly on the booster body. With this integral check valve and vacuum chamber, it is possible to obtain several power assisted brake applications with the engine shut off. This arrangement makes a vacuum reservoir unnecessary. For a greater reserve, however, a vacuum reservoir is available as optional equipment on some trucks. Either vacuum from the forward side of the diaphragm or air from the bellows (atmospheric chamber) can be connected to the rear side of the diaphragm through porting in the control valve hub and the plunger assembly. APPLIED POSITION As the brake pedal is depressed, the valve operating rod and valve plunger assembly move forward com- DIAPHRAGM ATMOSPHERIC PORT OPEN VACUUM PORT CLOSED ATMOSPHERIC PORT CLOSED o\ BRAKE PEDAL H1273-A H1274-A
2-42 GROUP 2 - BRAKES DIAPHRAGM RETURN SPRING VACUUM PORT OPEN HOLDING POSITION When the forward motion of the brake pedal is stopped and held, the valve operating rod ceases to move the control valve plunger forward. However, the un-balanced forces of atmospheric pressure and vacuum on each side of the diaphragm will continue to move the outer sleeve of the control valve plunger forward keeping the vacuum porting closed. At the same time, the reaction force acting through the reaction ring and lever assembly will tend to move the atmospheric valve to the closed position (Fig. 9). When these combined forces balance, the porting to the vacuum supply will remain closed and the atmospheric valve will cut off any further passage of atmospheric pressure to the area behind the diaphragm. Therefore, the power assist force acting on the master cylinder piston will stabilize and the hydraulic force applying the brakes will be maintained at a constant level. RELEASED POSITION (VACUUM |^j ATMOSPHERIC PRESSURE FIG. 10—Booster in Released Position pressing the plunger return spring (Fig. 8). The initial movement of the plunger closes the porting from the vacuum chamber preventing further evacuation of the area back of the diaphragm. Further movement of the plunger forces the atmospheric valve off its seat so that atmospheric pressure from the bellows can enter the hub porting that leads to the rear side of the diaphragm. With vacuum on the front side of the diaphragm, and atmospheric pressure on the back side of the diaphragm, a force is developed to move the diaphragm, push rods and master cylinder piston forward to close the compensating port and force hydraulic fluid under pressure through the hydraulic check valve and brake tubes to the wheel brakes. As hydraulic pressure is developed in the hydraulic system, a reaction counter-force acts against the reaction lever and ring assembly. This H1275-A reaction lever and ring assembly is designed to transmit the reaction forces back through the actuating control valve assembly to the brake pedal and provide the driver with a resistance that is in proportion to the brake hydraulic apply forces. This is the means of providing the proper "driver feel" to the power brake unit. When the pedal presure is released from the valve operating rod and plunger assembly, the plunger return spring moves the plunger away from the atmospheric valve allowing the valve to seat against the hub (Fig. 10). This seating of the valve closes off the bellows chamber from the hub porting that connects to the rear side of the diaphragm. At the same time, the rearward movement of the plunger opens the porting from the vacuum chamber and draws out the air from the rear side of the power diaphragm. With vacuum on both sides of the diaphragm, the assist force against the master cylinder push rod is eliminated. The brake shoe retracting springs will, therefore, cause the hydraulic fluid to return the master cylinder piston, push rods, control valve plunger assembly and the diaphragm to the released position. With the piston and push rods in the released position, the hydraulic compensating port in the master cylinder is open. The open port permits fluid either to return from the brake system to the fluid reservoir, or enter the brake system from the reservoir. IN-TRUCK ADJUSTMENTS AND REPAIRS DASH-MOUNTED BOOSTER PUSH ROD ADJUSTMENT The push rod is provided with an adjustment screw to maintain the correct relationship between the booster control valve plunger and the master cylinder piston. Failure to maintain this relationship will prevent the master cylinder piston from completely releasing hydraulic pressure and can cause the brakes to drag. Remove the master cylinder for access to the booster push rod. To check the adjustment of the screw, fabricate a gauge of the dimensions shown in Figs. 11 or 12. Then place the gauge against the master cylinder mounting surface of the booster body as shown in Figs. 13 or 14. The push rod screw should be adjusted so that the end of the screw just touches the inner edge of the slot in the gauge. FIG. 11-Push Rod Gauge Dimensions Bendix Booster— F-100 and F-250 H1329-B
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Page 6 and 7: VEHICLE IDENTIFICATION SERIES - (LE
Page 8 and 9: Q 1 I o I- o I UJ U 1 s CD (3 II CD
Page 10 and 11: 1965 FORD TRUCK IDENTIFICATION INTE
Page 12 and 13: 1965 FORD TRUCK IDENTIFICATION REAR
Page 14 and 15: 2-1 ; . BRAKES ; .•/•.' ' ' ' -
Page 16 and 17: PART 2-1-GENERAL BRAKE SERVICE 2-3
Page 22 and 23: PART 2-1 -GENERAL BRAKE SERVICE 2-9
Page 24 and 25: PART 2-2 HYDRAULIC BRAKES Section P
Page 26 and 27: PART 2-2-HYDRAULIC BRAKES 2-13 IN-T
Page 28 and 29: PART 2-2-HYDRAULIC BRAKES 2-15 2. T
Page 30 and 31: PART 2-2-HYDRAULIC BRAKES 2-17 3. I
Page 32 and 33: PART 2-2-HYDRAULIC BRAKES 2-19 4. R
Page 34 and 35: PART 2-2-HYDRAULIC BRAKES 2-21 BRAK
Page 36 and 37: PART 2-2 - HYDRAULIC BRAKES 2-23 4.
Page 38 and 39: PART 2-2 - HYDRAULIC BRAKES 2-25 2.
Page 40 and 41: PART 2-2-HYDRAULIC BRAKES 2-27 STOP
Page 42 and 43: PART 2-3 Section PARKING BRAKES Pag
Page 44 and 45: PART 2-3-PARKING BRAKES 2-31 system
Page 46 and 47: PART 2-3-PARKING BRAKES 2-33 INSTAL
Page 48 and 49: PART 2-3-PARKING BRAKES 2-35 6. Rem
Page 50 and 51: PART 2-4-VACUUM BOOSTERS 2-37 BENDI
Page 52 and 53: PART 2-4-VACUUM BOOSTERS 2-39 force
Page 56 and 57: PART 2-4 - VACUUM BOOSTERS 2-43 I |
Page 58 and 59: MAJOR REPAIR OPERATIONS PART 2-4 -
Page 60 and 61: PART 2-4-VACUUM BOOSTERS 2-47 SEAL
Page 62 and 63: PART 2-4 - VACUUM BOOSTERS 2-49 sna
Page 64 and 65: PART 2-4 - VACUUM BOOSTERS 2-51 MID
Page 66 and 67: PART 2-4 - VACUUM BOOSTERS 2-53 exc
Page 68 and 69: PART 2-4 - VACUUM BOOSTERS 2-55 NUT
Page 70 and 71: PART 2-4 - VACUUM BOOSTERS 2-57 LOC
Page 72 and 73: PART 2-4 - VACUUM BOOSTERS 2-59 PUS
Page 74 and 75: PART 2-5 AIR-HYDRAULIC BOOSTER Sect
Page 76 and 77: PART 2-5 - AIR-HYDRAULIC BOOSTER 2-
Page 78 and 79: PART 2-5 - AIR-HYDRAULIC BOOSTER 2-
Page 80 and 81: PART 2-6 AIR SUPPLY SYSTEM Section
Page 82 and 83: PART 2-6 - AIR SUPPLY SYSTEM 2-69 r
Page 84 and 85: PART 2-6 - AIR SUPPLY SYSTEM 2-71 A
Page 86 and 87: PART 2-6 - AIR SUPPLY SYSTEM 2-73 I
Page 88 and 89: PART 2-7-AIR BRAKES 2-75 PLUNGER RU
Page 90 and 91: PART 2-7-AIR BRAKES 2-77 on bracket
Page 92 and 93: PART 2-7-AIR BRAKES 2-79 DASH FLOOR
Page 94 and 95: REMOVAL AND INSTALLATION PART 2-7-A
Page 96 and 97: PART 2-7-AIR BRAKES 2-83 2. Positio
Page 98 and 99: PART 2-7-AIR BRAKES 2-85 tion of th
Page 100 and 101: PART 2-8-SPECIFICATIONS 2-87 FRONT
Page 102 and 103: INTERNAL EXPANDING SHOE TYPE PARKIN
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PART 2-8 - SPECIFICATIONS 2-91 FRON
Page 106 and 107:
PART 2-8-SPECIFICATIONS 2-93 FRONT
Page 108 and 109:
PART 2-8 - SPECIFICATIONS 2-95 REAR
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DEMO - 1965 Ford Truck Shop Manual - ForelPublishing.com

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