42–11 Hydro-Max
™
Brake
System Inspection
NOTE: The following instructions apply to
Bendix and Bosch Hydro-Max systems.
1. Check the fluid level in the hydraulic brake fluid
reservoir. If needed, fill the reservoir up to the
bottom of the fill-neck. See
Fig. 15. Use only
heavy-duty brake fluid, DOT 3.
2. Check all hydraulic lines and fittings for damage,
leakage, or looseness.
Replace damaged or leaking components, and
tighten loose fittings.
3. Check the brake module for leaks. If leaks are
found, repair or replace the brake module. See
Group 42 of the Business Class M2 Plus
Workshop Manual for replacement instructions,
or take the vehicle to an authorized Freightliner
dealer.
4. Check the electrical connections and harnesses.
Make sure the connectors are fully seated and
the harnesses are not chafed or cut. Repair or
replace any damaged harness. Disconnect any
loose connectors and inspect the terminals for
corrosion. If corrosion is present, replace the
terminals. If corrosion is not present, reconnect
the connector.
5. Check the fuse for the hydraulic brake booster
pump, as follows.
5.1 Open the cover to the main power
distribution module (PDM).
5.2 Pull the fuse in position F6 for the Hydro-
Max relay.
5.3 Inspect the relay to make sure the fuse is
not damaged. If the fuse is damaged,
install a new fuse. If the fuse is not
damaged, install the fuse in position F6.
5.4 Close the PDM cover.
6. Check the operation of the Hydro-Max brake
booster, as follows.
6.1 With the engine off, depress the brake
pedal; the warning light and buzzer
should come on, and the electric motor
should run.
6.2 Start the engine and allow the gauges to
sweep. Depress the brake pedal; no
warning lights, buzzer, or electric motor
should come on.
42–12 WABCO System Saver
Air Dryer Desiccant
Cartridge Replacement
NOTE: The following instructions apply to the
System Saver 1200, 1200 Plus, and Twin air
dryers.
NOTICE
The WABCO System Saver air dryers can use
either a standard or oil coalescing desiccant
cartridge. When replacing the desiccant cartridge,
it is very important to use the same type of
cartridge that was originally installed on the dryer.
Oil coalescing cartridges can be used in any
08/03/2015
f460513c
A
B
A. Open caps and check fluid level.
B. Fill to this level.
Fig. 15, Hydraulic Brake Fluid Reservoir (Bosch
reservoir shown, Bendix reservoir similar)
Brakes 42
Business Class M2 Plus Maintenance Manual, 02/10/2023 42/17
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