8.4.1. cylinder repairs (page 2 of 2)

Fig. 8.19. — Sectional view of the brake servo unit with two working chambers. The push rod of this type of servo unit must not be adjusted.

Figs. 8.18 and 8.19 show sectional views of the two servo units, where you can see the difference. The push rod (5) has been factory-adjusted on the double-chamber unit and must not be disturbed. The push rod must, however, be adjusted in the case of a single-chamber unit, but differences must be noted. Dimension "L" must be set to 105 - 106 mm if the vehicle is built up to September 1990. After this date the dimension is 113 - 115 mm. We must mention that the new dimension has not been introduced at the same time on all vehicles.

There are times when a brake servo unit can be obtained from a breakers yard. To fit the correct one, follow the guide lines below:

• If the height "H" of the studs is 22.5 mm and the servo unit has a diameter of 8 in. it can be used in a vehicle built before September 1990 (servo unit with one chamber, Fig. 8.18).
• If the height "H" of the studs is 32.0 mm and the servo unit shown in Fig. 8.18 has a diameter of 8 in., you can use it in vehicles build from October 1990.
• If the height "H" of the studs is 35.0 mm and the servo unit shown in Fig. 8.18 has a diameter of 9 in., the unit will be suitable in vehicles build after January 1992.
• If the brake servo unit has the shape shown in Fig. 8.19 (two chambers) the height "H" will be 20.5 mm to June 1990 and then 29.5 mm.

The master cylinder must be removed to gain access to the brake servo unit. The servo unit can be unscrewed from the inside of the vehicle, but the spare wheel carrier may have to be removed to lift out the unit.