GENERAL
Great cleanliness is essential when dealing with any part of the hydraulic system and especially when the brake fluid is concerned. Dirty or aerated brake fluid must never be used in the hydraulic system.
Use only the recommended type of brake fluid for topping up the master cylinder reservoir.
BLEEDING THE HYDRAULIC SYSTEM
Bleeding or expelling air from the hydraulic system Is not a maintenance operation and will only be necessary when a portion of the hydraulic system has been dis-connected or when the fluid level In the master cylinder reservoir has fallen so low that air has entered the system.
Always keep a careful check on the fluid level in the master cylinder reservoir during bleeding since It Is most Important that a high level of fluid is maintained. Should air enter the master cylinder from the reservoir, the complete operation must be repeated.
1. Destroy all vacuum in the servo unit by repeated operation of the brake pedal, otherwise difficulty will be experienced in completely expelling the air from the hydraulic system. Do NOT start the engine before bleeding the system has been completed.
2. Ensure that all hydraulic connections are secure and the master cylinder reservoir is filled to the correct level; this level must be maintained during the complete operation.
3, Remove the rubber dust cap from the bleed screw of the left hand rear wheel cylinder, fit the bleed tube and immerse the free end of the bleed tube In a glass vessel, containing a small quantity of brake fluid.
4. Slacken the bleed screw three quarters of a turn and with the assistance of another person, depress the brake pedal a full stroke and allow the pedal to return as quickly as possible, any check In the return travel will prevent effective bleeding; actuate the brake pedal in this manner until the brake fluid entering the glass vessel is free from air bubbles and then tighten the bleed screw during the next downward stroke of the brake pedal, to the specified torque loading, see under "Bleed screws
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5. Remove the bleed tube and glass vessel from the bleed screw and fit the rubber dust cap.
6. Repeat the previous three operations with the bleed screws of the front brake calipers, finishing at the right hand bleed screw which is nearest to the master cylinder.
7. Top up the master cylinder reservoir and refit the filler cap ensuring its seal Is In good condition and its air vent is unobstructed, as the latter may cause pressure to build up and the brakes to bind.
Bleed screws
The calipers and wheel cylinder have conical ended bleed screws which bed on to a seat formed in the bottom of the bleed screw tapping in the body of that particular component.
The bleed screws must never be over tightened since their threads may become stripped. Use only short spanners of 4 to 5 in. (10 to 12-5 cm) In length to tighten bleed screws.
The torque loading is: —
5 to 7.5 lb. ft. (0.69 to 1.0 kg. m.).
Checking for leaks
1. Clean the connections, metal pipes and flexible hoses of all road dirt.
2. Start and run the engine when inspecting the hydraulic system after the vacuum servo unit. THIS IS IMPORTANT.
3. Apply firm pressure to the brake pedal for a number of seconds while an assistant examines the con-nections, metal pipes and flexible hoses for leakage.
4. When leakage is observed at the connections, it may be necessary to dismantle the faulty connection to determine the cause, for tightening the bleed screw or union nut may only lead to stripped threads. Leaking metal pipes or flexible hoses must be renewed.
After making any disconnections it will be necessary to bleed the hydraulic system of air, see under" Bleeding the hydraulic system".
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