Section 12: BRAKE AND AIR SYSTEM
PA1562
9
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.
8.2 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.
8.3 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 should be used to replace
existing nylon lines only, and must comply
with the color identification code to ease
pneumatic system troubleshooting.
8.4 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.
8.5 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.
8.6 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.
9. PRESSURE REGULATING VALVES
There is one pressure regulator for the belt
tensioners, and an optional 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
doors and is used to limit the air pressure in belt
tensioners to 50 ± 2 psi (345 ± 15 kPa) (Fig. 7).
The optional regulator is located near the
Webasto in the engine compartment (accessible
through the engine R.H. side door). It is used for
transmission retarder and should be adjusted to
80 ± 3 psi (550 ± 20 kPa).
Air Pressure
(psi)
Air Pressure
(kPa)
Belt
Tensioner
Series 60
50
Series 60
345
Retarder 80 ± 3 550 ± 20
9.1 MAINTENANCE
Every 100,000 miles (160 000 km) or once every
two years, whichever comes first, disassemble
the regulating valve and wash all metal parts in
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