Section 12: BRAKE AND AIR SYSTEM
8 X3-45 Commuter PA1593 DOB 2400-2489 Section 12 Updated Sept. 2015
year, whichever comes first. Tighten or replace
when necessary. When replacing copper piping,
the parts must be free of burrs, copper cuttings,
and dirt. Blow out piping with compressed air.
Any such particles will destroy sealing seats in
air control units. Also, new piping must be the
same size as the old one.
9.2 FLEXIBLE HOSES
A flexible hose is used normally where it is
impractical to use copper or nylon tubing due to
constant flexing during operation, such as brake
chamber hoses. Hose connections should be
tested for leakage at least every 6,250 miles
(10 000 km) or twice a year, whichever comes
first and tightened or replaced if necessary. Any
hose which is chafed, worn or kinked should be
replaced.
Teflon-braided stainless steel hoses used in the
engine compartment must be replaced only with
similar hoses.
9.3 NYLON TUBING
Nylon tubing is used for air lines in areas where
usage of this material is suitable. Nylon tubing is
flexible, durable, and weather resistant. When
replacing an air line, use nylon tubing only where
it has been used previously.
Nylon air lines must never be routed in areas
where temperature could exceed 200
o
F (93
o
C).
CAUTION
Nylon air lines shoul
existing nylon lines only, and must comply with
the color identification code to ease pneumatic
system troubleshooting.
9.4 AIR LINE OPERATING TEST
If any trouble symptom such as slow brake
application or slow brake release indicates a
restricted or clogged air line, disconnect the
suspected tube or hose at both ends and blow
through it to clear the passage.
Inspect tubing and hose for partial restriction that
may be caused by dents or kinks. If such a
condition is found, the tubing or hose should be
replaced.
9.5 AIR LINE LEAKAGE TEST
With air system fully charged and the brakes
applied, coat all tubing and hose connections
with a soapy solution to check for air leakage.
No leakage is permitted. Leakage can
sometimes be corrected by tightening the
connection. If this fails to correct the leakage,
new fittings, nylon tubing, copper tubing,
teflon-braided stainless steel and flexible hoses
must be installed as applicable.
9.6 MAINTENANCE
Inspect all lines for cuts, swelling, kinks or other
damage or deterioration. Check for lines being
pinched by other components. Retaining clips
and ties must be in place.
Any support or bracket should be in good
condition and mounted firmly in position. Hose
spring guards should be in usable condition and
not distorted. Particular attention should be given
to long lines. Any supporting component (clips,
ties, grommets, etc.) must be secured to prevent
against unnecessary vibration and eventual
loosening of connection. Any detected leak
should be repaired. Be sure nylon lines are not
near areas of intense heat. Check for any
missing grommets or loose material where
chafing or cutting may occur. Replace with new
material as required. In general, lines should be
securely located in position and free from any
binding condition which would hinder air flow.
10. PRESSURE REGULATING VALVES
There is one pressure regulator for the belt
tensioners, and another one installed on vehicles
equipped with the World transmission output
retarder.
The belt tensioner pressure regulating valve is
located in the engine compartment above the
engine air filter and is used to limit the air
pressure in belt tensioners to 45 ± 2 psi (310 ±
15 kPa) (Fig. 7).
The other regulator is located in the engine
compartment, on the engine cradle R.H. side
(accessible through the engine R.H. side door).
It is used for transmission retarder and should
be adjusted to 85 ± 3 psi (586 ± 20 kPa).
Air Pressure
(psi)
Air Pressure
(kPa)
Belt Tensioner 45 310
Retarder 85 586
10.1 MAINTENANCE
Every 100,000 miles (160 000 km) or once every
two years, whichever comes first, disassemble
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