Brake Booster/Brake Master Cylinder, Overview

Hydraulic Unit, Brake Booster/Master Cylinder, Overview

Note:
^ Complete brake master cylinders and brake boosters can be replaced separately

1. Brake Booster
^ For gasoline engines vacuum is taken from the intake manifold
^ Diesel engines have a vacuum pump to create the required vacuum
^ Functional check:
- With engine switched off, depress brake pedal firmly several times (to exhaust vacuum in the unit)
- Hold brake pedal with average foot pressure in brake position and start engine. If brake booster is functioning properly, brake pedal should give noticeably underfoot.
^ If pedal does not give, replace brake booster
^ Check valve (in vacuum hose). Refer to Vacuum Pump.
^ Functional check
^ Separating from brake pedal. Refer to Brake pedal to brake booster, disconnecting and connecting.
^ Removing and installing. Refer to Brake Booster.
2. Cap
3. Brake fluid reservoir
4. Plug
^ Coat with brake fluid and press into reservoir
5. Retaining pin
^ Insert through brake master cylinder
6. Brake master cylinder
^ Cannot be repaired. If faulty, replace as complete unit
7. Hex nut, self-locking 20 Nm (15 ft. lbs.)
8. Bolt, 8 Nm (70 inch lbs.)
9. Cap nut, 20 Nm (15 ft. lbs.)
10. ABS/EDL hydraulic unit
11. ABS control module
^ Control module connector is not disconnected before On Board Diagnostic (OBD)
12. Connection for brake line
^ Hydraulic unit to left front brake caliper
13. Connection for brake line
^ Hydraulic unit to right rear wheel cylinder/ brake caliper
14. Connection for brake line
^ Hydraulic unit to left rear wheel cylinder/brake caliper
15. Connection for brake line
^ Hydraulic unit to right front brake caliper
16. Brake line
^ Brake master cylinder/pressure rod piston circuit to hydraulic unit
17. Brake line
^ Brake master cylinder/floating piston circuit to hydraulic unit
18. Hex nut, self-locking, 20 Nm (15 ft. lbs.)
19. Hex nut, self-locking, 20 Nm (15 ft. lbs.)
20. Seal
^ Always replace
21. Vacuum hose
^ Install in brake booster
22. Scaling plug
23. Hex nut, self-locking, 20 Nm (15 ft. lbs.)
24. Seal
^ For brake booster
25. Boot
^ Ensure boot is properly seated or suction noises may be noticed
26. Bracket

Brake Lines From Brake Master Cylinder To Hydraulic Unit, Connecting





Fig. 1 Vehicles with ABS
A -Secondary piston circuit
B-Primary piston circuit
1. Hydraulic unit to right front brake caliper
2. Hydraulic unit to left rear wheel cylinder/brake caliper
3. Hydraulic unit to right rear wheel cylinder/brake caliper
4. Hydraulic unit to left front brake caliper





Fig. 2 Vehicles with ABS/EDL
A-Secondary piston circuit
B-Primary piston circuit