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M.Ot.TIBESJOS^ HANDBOOK FOR BRAKE SERVICE Hydraulic Broke Systems (Continued1 Tfifj give* right end left hani cylinder* which are not inferchangeable a auch. Accordingly, in cate of removal of thete cylinders care must be exercised in their replacement. On 1935 StudcbaVer models the large bore it alway* assembled toward the front of the car. (See maintenance note under Hydraulic Brakes.) On the Chrysler cars the large bore i always assembled toward the rear of the car. The cylinders are marked (R) to indicate the reverse acting shoe connection. As the front wheel brake cylinders are different from the rear wheel brake cylinders in their cylinder bore sires, they should never be interchanged front and rear, as it would cause badly unbalanced brakes. Maintenance Suggestions 1. Master cylinder supply tank should be kept full of Sold. *' 2. Air vent at top of vent cap (N) should be kept open and free from dirt. 3. Compensating port hole (C) must be kept open. Locked brakes, spongy pedal, and no brakes at all may all be cauaed by blocking of the compensating port hole. 4. ONE HALF-INCH FREE* MOVEMENT OF ROD (A) IS NECESSARY WHEN PEDAL IS RELEASED. Should rod be adjusted tightly against piston (B) then compensating port hole (C) will be blocked by cup (D) and com* penaating action of master cylinder will be destroyed. J. Examine cups (D) and (P) occasionally and,*if swelled, replace. 5. Leakage of fluid past piston (E) may be partially remedied by the replacement of cups (F) but, if cylinder walla are scratched, reluming is necessary. T. Bleeding the system. (Whenever system has been disconnected or when air it found In the system It is necessary to bleed the lines.) (a) Fill supply tank with fluid. (An automatic refiller bottle like Fig. 1, Rage 36, will prevent master cylinder from running dry during bleeding.) (b) Remove cap from bleeder valva (GJ and screw in bleeder drain--brass fitting with rubber tube attached--tbe end of which is immersed in clean container partially filled with brake fluid. (c) Allow tube to bang in dean container--unscrew bleeder connection fi turn* and depress foot pedal slowly by hand to half the limit of its travel, allowing spring to return pedal to on position. End of rubber hose should be kept below surface of liquid in container. When all air bubbles cease to appear (approximately 6 to 10 half strokes of pedal will be necessary to bleed each wheel cylinder) close bleeder connection. (d) Repeat on each wheel cylinder--making sure that supply tank it filled after bleeding each wheel. Fluid withdrawn in the bleeding should not be used again. (e) When bleeding operation is completed, the fluid reservoir mast be refilled to within 54' of the top. 8. Conditioning Hydraulic system for extreme cold weather condition*. (This procedure should be followed In all sections of the country where zero tempera tures are experienced daring winter months.) (s) Use light metal cop expander Inside rubber cups (Pi) to hold skirts of cup more closely to the cylinder walla. (Extreme cold weather causes slight shrinkage of rubber cupr. The expander is of no value to increase the piston seal until the akirt of the rubber cup contracts due to cold.) (b) Use sti/Ter coil spring (D,) between the two wheel cylinder pistons. These heavier springs are usually dull in finish in contrast to the standard spring, which is quite shiny. (c) Driin and refill system with special cold weather hydraulic fluid. 9. Use genuine hydraulic brake fluid. Engine or any mineral oil will render the brakes inoperative and will necessitate replacement of all rubber parts in the system. 4b i \ 4 V }* j * I > 1 1 r t i MULTIBESTOS HANDBOOK FOR BRAKE SERVICE VACUUM POWER BRAKES *ThERE ere two types of Vacuum Brake Systems now in use: 1. Air Suspended Type: Thin system utilizes the vacuum created in the ;r*ake manifold to operate (within a cylinder) a piston which is comu'C*cd to ;> Ywr on the brake cro* haft. The air suspended system is plway* used in c^nunittion wi*S an external valve, either pul! or pusher type, depending upon room for installation. Z. Vacuum Suspended Type: (a) Plain cylinder with external valve. This tystrm also utilize* the vacuum created :n *.'ic intake manifoV but differs from the a^r suspended type insofar as 'he entire system is contantly under vacuum. Admission of air to one ide of the booster cylinder by mean* of the external valve applies tbe pressure to the braking system. (b) Internal Valve Type Cylinder: This system i under vacuum at all times when 'he engine is running and is similar to (a) except that the valve controlling intake of air to the cylinder is built within the cylinder itself. Irrespective of the type of vacuum system, the following principle* apply: Pressure on the foot pedal operates a valve that allows air to enter the booster cylinder in the case of the vacuum suspended type, or air to be drawn from the cylinder in tbe case of the air suspended type. The thrust, caused by tbe difference in pressure at the piston surfaces, is trans ferred by means of a piston rod either to a single cross shaft actuating both front and rear brakes or to separate cross shafts mounted at front and rear of car operating the front and rear brakes respectively. (When a hydraulic system is used the piston rod is attached directly to the master cylinder.) The booster valve (or cylinder with internal valve) is bo mounted on the frame that when pedal is only partially depressed the brake will be only partially applied. Thu is the so-called "holding" position. The mechanism o{ the system is such that the port hole in the valve is closed after the brake rods have travelled a prescribed distance as controlled by the foot pedal. This arrangement allows partial brake application for stopping slowly or bolding back loads on steep grades. Certain booster systems (air suspended type) have a dash control valve to prevent overbraking in wet, icy, and snowy weather. This valve regulaee* the amount of vacuum taken from the manifold. A relay valve is used ;n tractor trailer installations to overcome the "time lag" which would be encountered if no relay valve were used. The connection between control valve and relay valve is a yAm pipe. Immediately upon operation of the control valve, air Is admitted through this line to the relay valve which operates the rparate booster system on tbe trailer. In synchronism with the control valve on the tractor the relay valve allows perfect control of the braking system no matter how long the trailer train may be. Mointenance Suggestions As a general statement, there should be no occasion to adjust any power unit or brake assister unless it has been tampered with or damaged in an accident or removed and disassembled. All adjustments to power units a^e externa!. For complete details on the different brakei we refer you to Mr. Paul Dumas's book entitled "Brakei.** In case of trouble or replacement of the internal parts it is recommended that the power unit should be taken to an official service station fur repairs (BK, Bes'.Ur, or car distributor). 47