Mercedes-Benz Sprinter / Dodge Sprinter. Service manual — part 192
NOTE: The pressure gauge, connected at the ALB
controller must indicate the outlet pressure which
is assigned on the ALB plate to the rear axle load
determined.
NOTE: If the rear axle load determined is between
two figures indicated on the ALB plate, the outlet
pressure should be determined accordingly.
(8) If the pressure measured differs from the spec-
ification, adjust the ALB controller (Fig. 16).
(9) Loosen the brake pedal winch.
(10) Adjust the outlet pressure by turning the
adjusting nut (Fig. 16) To increase pressure -
tighten the adjusting nut. To reduce pressure -
loosen the adjusting nut.
(11) After adjustment reinstall the brake pedal
winch and recheck the pressures and readjust if
needed.
(12) Tighten the lock adjusting nut.
MASTER CYLINDER
DIAGNOSIS AND TESTING - MASTER CYLIN-
DER / POWER BOOSTER
(1) Start engine and check booster vacuum hose
connections. A hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neu-
tral.
(3) Pump brake pedal until all vacuum reserve in
booster is depleted.
(4) Press and hold brake pedal under light foot
pressure. The pedal should hold firm, if the pedal
falls away master cylinder is faulty (internal leak-
age).
(5) Start engine and note pedal action. It should
fall away slightly under light foot pressure then hold
firm. If no pedal action is discernible, power booster,
vacuum supply, or vacuum check valve is faulty. Pro-
ceed to the POWER BOOSTER VACUUM TEST.
(6) If the POWER BOOSTER VACUUM TEST
passes, rebuild booster vacuum reserve as follows:
Release brake pedal. Increase engine speed to 1500
rpm, close the throttle and immediately turn off igni-
tion to stop engine.
(7) Wait a minimum of 90 seconds and try brake
action again. Booster should provide two or more vac-
uum assisted pedal applications. If vacuum assist is
not provided, booster is faulty.
POWER BOOSTER VACUUM TEST
(1) Connect vacuum gauge to booster check valve
with short length of hose and T-fitting (Fig. 17).
(2) Start and run engine at curb idle speed for one
minute.
(3) Observe the vacuum supply. If vacuum supply
is not adequate, repair vacuum supply.
(4) Clamp hose shut between vacuum source and
check valve.
(5) Stop engine and observe vacuum gauge.
(6) If vacuum drops more than one inch HG (33
millibars) within 15 seconds, booster diaphragm or
check valve is faulty.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2) Remove check valve and valve seal from
booster.
Fig. 16 ALB CONTROLLER ADJUSTER NUT
1 - ALB ADJUSTER NUT
2 - SPRING
Fig. 17 Typical Booster Vacuum Test Connections
1 - TEE FITTING
2 - SHORT CONNECTING HOSE
3 - CHECK VALVE
4 - CHECK VALVE HOSE
5 - CLAMP TOOL
6 - INTAKE MANIFOLD
7 - VACUUM GAUGE
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BRAKES - BASE
5 - 17
(3) Use a hand operated vacuum pump for test.
(4) Apply 15-20 inches vacuum at large end of
check valve (Fig. 18).
(5) Vacuum should hold steady. If gauge on pump
indicates vacuum loss, check valve is faulty and
should be replaced.
STANDARD PROCEDURE - MASTER CYLINDER
BLEEDING
A new master cylinder should be bled before instal-
lation on the vehicle. Required bleeding tools include
bleed tubes and a wood dowel to stroke the pistons.
Bleed tubes can be fabricated from brake line.
(1) Mount master cylinder in vise.
(2) Attach bleed tubes to cylinder outlet ports.
Then position each tube end into reservoir (Fig. 19).
(3) Fill reservoir with fresh brake fluid.
(4) Press cylinder pistons inward with wood dowel.
Then release pistons and allow them to return under
spring pressure. Continue bleeding operations until
air bubbles are no longer visible in fluid.
REMOVAL
(1) Using a suction gun remove as much brake
fluid from the reservoir as possible (Fig. 20).
(2) Remove the fluid reservoir (Fig. 20) or (Fig. 21)
(Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/
FLUID RESERVOIR - REMOVAL).
(3) Remove the brake lines Seal off the ends and
bore holes with plugs. (Fig. 20) or (Fig. 21)
(4) Remove the master cylinder mounting nuts
(Fig. 20) or (Fig. 21). Check brake booster for
damage due to leaking master cylinder. It is not
possible to repair the master cylinder.
Fig. 18 Vacuum Check Valve And Seal
1 - BOOSTER CHECK VALVE
2 - APPLY TEST VACUUM HERE
3 - VALVE SEAL
Fig. 19 Master Cylinder Bleeding–Typical
1 - BLEEDING TUBES
2 - RESERVOIR
Fig. 20 MASTER CYLINDER
1 - SUCTION GUN
2 - BRAKE FLUID CAP
3 - BRAKE FLUID LEVEL INDICATOR
4 - O-RING
5 - NUT
6 - BRAKE LINE
7 - MASTER CYLINDER
8 - FLUID RESERVOIR
5 - 18
BRAKES - BASE
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INSTALLATION
(1) Install the master cylinder to the brake booster
(Fig. 20). Tighten to 28 N·m (248 in. lbs.).
(2) Install the brake lines (Fig. 20). Tighten to 14
N·m (124 in. lbs.).
(3) Install the fluid reservoir (Fig. 20) (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/FLUID RES-
ERVOIR - INSTALLATION).
(4) Bleed the brake system.
(5) Check the brake system for any leaks.
PEDAL
REMOVAL
(1) Remove the master cylinder (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/MASTER
CYLINDER - REMOVAL).
(2) Remove the retainer and pin for the master
cylinder push rod (Fig. 22).
(3) Remove the retainer and pin for the brake
pedal pivot bolt (Fig. 22).
(4) Unhook the spring and remove the brake pedal
(Fig. 22).
(5) Disconnect the plug connector on the stop lamp
switch (Fig. 22).
(6) Remove the bolts and remove the pedal bearing
bracket (Fig. 22).
INSTALLATION
(1) Install the bolts for the pedal bearing bracket
(Fig. 22). Tighten to 23 N·m (204 in. lbs.)
(2) Reconnect the plug connector for the stop lamp
switch (Fig. 22).
(3) Install the brake pedal and hook the spring
(Fig. 22).
(4) Install the retainer and pin for the brake pedal
(Fig. 22).
(5) Install the retainer and pin for the master cyl-
inder push rod (Fig. 22).
(6) Install the master cylinder (Refer to 5 -
BRAKES/HYDRAULIC/MECHANICAL/MASTER
CYLINDER - INSTALLATION).
POWER BRAKE BOOSTER
DESCRIPTION
All models use a tandem diaphragm, power brake
booster.
NOTE: The power brake booster is not a repairable
component. The booster must be replaced as an
assembly if diagnosis indicates a malfunction has
occurred.
OPERATION
The booster unit consists of a single housing
divided into two by a tandem diaphragm. The outer
Fig. 21 MASTER CYLINDER (DRW)
1 - POWER BRAKE BOOSTER
2 - RESERVOIR
3 - BRAKE LINES
4 - PRESSURE PORTS
5 - MASTER CYLINDER
Fig. 22 BRAKE PEDAL
1 - MOUNTING BOLT
2 - PEDAL BEARING BRACKET
3 - STOP LAMP SWITCH
4 - CLIP
5 - PIVOT BOLT
6 - RETURN SPRING
7 - PEDAL
8 - PUSH ROD BOLT
9 - PUSH ROD
10 - CLIP
11 - BOLT
12 - WASHER
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BRAKES - BASE
5 - 19
edge of the diaphragm is secured to the housing. The
booster push rod, which connects the booster to the
brake pedal and master cylinder, is attached to the
center of the diaphragm. A check valve is used in the
booster outlet connected to the engine intake mani-
fold. Power assist is generated by utilizing a combi-
nation of vacuum and atmospheric pressure to boost
brake assist.
REMOVAL
(1) Using a suction gun remove as much brake
fluid from the reservoir as possible.
(2) Disconnect the brake level switch electrical
connector.
(3) Remove the brake lines from the master cylin-
der Seal off the ends and bore holes with plugs.
(4) Remove the master cylinder from the booster.
(5) Remove the booster vacuum hose and check
valve (Fig. 23).
(6) Remove the pedal push rod clip (Fig. 23).
(7) Remove the booster mounting nuts (Fig. 23).
(8) Remove the booster from the vehicle.
INSTALLATION
(1) Install the brake booster to the vehicle.
(2) Install the booster mounting nuts (Fig. 23).
Tighten to 25 N·m (221 in.lbs.).
(3) Install the push rod pin & clip (Fig. 23).
(4) Install the brake booster vacuum line and
check valve (Fig. 23).
(5) Install
the
master
cylinder
to
the
brake
booster. Tighten to 28 N·m (248 in.lbs.).
(6) Install the brake lines to the master cylinder.
Tighten to 14 N·m (124 in.lbs.).
(7) Install the brake level switch electrical connec-
tor.
(8) Bleed the base brake system (Refer to 5 -
BRAKES - STANDARD PROCEDURE).
ROTORS
REMOVAL
REMOVAL - FRONT (SRW)
(1) Raise and support the vehicle.
(2) Remove the front wheels.
(3) Remove the front brake pads (Fig. 24).
(4) Remove the caliper adapter (Fig. 24).
(5) Install two lug studs to secure the disc brake
rotor when the locking bolt is removed.
(6) Remove the locking bolt for the disc brake rotor
(Fig. 24).
(7) Remove the two lug nuts.
(8) Remove the disc brake rotor (Fig. 24).
REMOVAL - REAR (SRW)
(1) Raise and support the vehicle.
(2) Remove the rear wheels.
(3) Remove the rear disc brake pads (Fig. 25).
(4) Remove the disc brake caliper adapter (Fig.
25).
(5) Apply the parking brake.
(6) Install two lug studs to secure the disc brake
rotor when the locking bolt is removed.
(7) Remove the locking bolt for the disc brake rotor
(Fig. 25).
(8) Remove the two lug nuts.
(9) Release the parking brake.
Fig. 23 POWER BRAKE BOOSTER
1 - VACUUM LINE & CHECK VALVE
2 - BRAKE BOOSTER
3 - GASKET
4 - MOUNTING NUTS (4)
5 - PUSH ROD PIN
6 - SECURING CLIP
Fig. 24 FRONT DISC BRAKE ROTOR
1 - CALIPER ADAPTER BOLT
2 - CALIPER ADAPTER
3 - GUIDE BOLT
4 - WEAR INDICATOR
5 - DISC BRAKE CALIPER
6 - DISC BRAKE PADS
7 - LOCKING BOLT
8 - DISC BRAKE ROTOR
5 - 20
BRAKES - BASE
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