Section 12: BRAKE AND AIR SYSTEM
Section 12 Updated Sept. 2015 X3-45 Commuter PA1593 DOB 2400-2489 9
the regulating valve and wash all metal parts in a
cleaning solvent (Fig. 7). Examine the
diaphragm; if cracked, worn or damaged,
replace with a new one. If the valve is excessive-
ly grooved or pitted, it should be replaced.
Replace any other part that appears worn or
damaged. After reassembly, adjust to the
specified pressure setting and check for air
leakage.
FIGURE 7: AIR PRESSURE REGULATING VALVE 12141A
10.2 PRESSURE SETTING PROCEDURE
Remove the dust cap from the pressure check
valve (Fig. 8). Attach a pressure gauge at this
port and check the pressure reading. If the
pressure reading is incorrect, adjust as follows:
FIGURE 8: AIR PRESSURE REGULATOR 12200
1. Loosen the locking nut, turn the adjustment
screw counterclockwise to decrease
pressure by approximately 10 psi (70 kPa)
below the required pressure.
2. Turn the adjustment screw clockwise to
increase the pressure slowly until the re-
quired pressure setting is reached. Tighten
the locking nut.
3. Remove pressure gauge and replace dust
cap on the air pressure check valve.
11. AIR COMPRESSOR
The Wabco System Saver 636 Twin Cylinder air
compressor is located on the alternator side of
the engine, at the flywheel end (Fig. 9). Its
function is to provide and maintain air under
pressure to operate devices in brake and air
systems.
The compressor is driven by the ring gear, and is
water cooled. Engine coolant is fed to the
compressor through a flexible hose tapped into
the block water jacket and connected to the rear
of the compressor. Coolant returns from the top
of the compressor (governor side) through a
flexible hose to the engine pump.
The air is taken from the air intake manifold and
entered in the top of the compressor. The
compressed air is pushed into the discharge line
located on side of the compressor, which sends
air to the air dryer. Lubricating oil is supplied to
the compressor by a line from the cylinder block
oil gallery connected to the air compressor.
Lubricating oil returns to the engine crankcase
through the air compressor drive assembly.
FIGURE 9: AIR COMPRESSOR LOCATION 03061
Maintenance and repair information on the
Wabco 636 Twin Cylinder air compressor is
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