SERVICING
Whenever possible the Girling Vacuum Servo Unit should be returned to the manufacturers for replacement but if this is not possible the renewing of all seals as contained in the Service Kit should provide a satisfactory unit providing the internal working surfaces are in good condition.
There should be no sign of corrosion, pitting, scoring or steps on the piston rod, pistons or bores and the surfaces should be smooth to the touch.
When dismantling, absolute cleanliness is essential. Wash the hands and lay out a clean sheet of paper on which to work and place the parts. Take care of all highly finished working surfaces on pistons, rods and bores. Clean hydraulic parts with Girling Cleaning Fluid, Alcohol or Girling Brake and Clutch Fluid (Crimson) and do not allow any other fluid, oil or grease to touch them. Special care should be exercised when removing or refitting the circlip in the hydraulic output cylinder and when re-assembling the vacuum cylinder to the body.
On some servo units a screw and locknut is fitted to the end cover, IN NO CIRCUMSTANCES MUST THE SCREW BE DISTURBED.
To remove and refit
1. Remove the vacuum hose from the top of the servo unit by withdrawing the banjo bolt and collecting the two washers.
2. Detach the hydraulic inlet and outlet pipes from the servo unit by releasing the union nuts and trapping any escaping fluid in a drip tray.
3. Detach the band round the vacuum cylinder from the "U" bracket by removing a nut, washer and bolt.
4. Remove the servo unit from the mounting bracket by withdrawing two bolts and washers. No useful purpose is served by removing the brackets.
5. Refitting is the reverse of the removal sequence but particular attention must be given to the following:—
(i) Check that the two brackets are secure and the "U" bracket points downward.
(ii) The vacuum pipe is secured with a washer each side of the banjo bolt.
(iii) The hydraulic system is bled of air, see under "Bleeding the hydraulic system" before the engine is started. |
To dismantle and re-assemble (Fig. 10)
1. Grip the servo unit in a vice by the two lower lugs onthe cast body.
2. Remove the piston assembly (5) spring (6) gasket (1) and end cover (15) from the vacuum cylinder (19) by removing the transfer pipe retaining plate and seven nuts and bolts while controlling the pressure of the spring (6). When fitted DO NOT DISTURB THE SCREW AND LOCKNUT IN THE END COVER (15).
3. Remove the vacuum cylinder (19) and gasket from the cast body (29) by withdrawing three bolts, washers and a clamping plate and easing the grommet in the flange of the cylinder from the transfer pipe (1 7).
4. Remove the cover and transfer pipe (17) from the valve chest (26) by withdrawing four screws and washers.
5. Remove the valve retainer and flat horseshoe spring from inside the valve chest (26) by withdrawing two screws.
6. Withdraw the valves (22 and 31) and "Tee" shaped lever (11) complete from inside the valve chest (26) by applying light pressure to the plug (8) in the end
of the control piston bore.
7. Remove the cast body (29) from the vice and withdraw the control piston assembly from the top bore by tapping the mounting flange of the cast body on a wooden block.
8. Dismantle the control piston assembly by compressing the piston spring, easing off the circlip and removing the spring and retainers.
9. Remove the two seals from the control piston and one from the plug (8).
10. Withdraw the piston rod bearing bush (23) from the output piston bore and using a hooked tool remove the gland seal beneath followed by the nylon spacer (24).
11. Mount the cast body vertically in the vice by one of the mounting lugs and fit the compression tool to press the output piston (25) into the bore. For the compression tool details see Fig. 11.
12. Using circlip pliers fully compress the circlip in the bore and carefully lift out the circlip exercising great care not to damage the bore, otherwise a brake failure may result. |
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