Page 126
TROUBLESHOOTING
앫 Switch operation sluggish — Check dash
switches, clutch switch or other control
switches. Readjust or replace as required.
Check clutch return springs for proper
operation. Check all controls for correct
operation and replace as required.
앫 Solenoid valve operation erratic — Check
solenoid valve using electrical specifications
presented in the table on page 121.
Disconnect the solenoid lead and provide
12 volts directly to the solenoid. Ensure that
the solenoid cap depresses.
Do not touch electrical connection when
system is energized.
OIL PRESSURE DROPPING BELOW MINIMUM
REQUIRED FOR ENGINE BRAKE OPERATION
앫 Upper solenoid O-ring/seal ring damaged
or missing — Remove the solenoid and
inspect the upper seal ring; if damaged,
replace all seal rings.
앫 Aeration of lubricating oil — Check for
aeration of the oil. Activate, then deactivate
engine brake and observe escape oil
coming from control valve cover. If oil has
bubbles or is foamy, air is present in system.
Aeration can be caused by an overfilled or
underfilled crankcase, or a crack or other
leak in the oil pickup tube. Correct in
accordance with MACK procedures.
앫 Lubricating oil being diluted by fuel oil —
Have an oil analysis of lube oil to determine
if fuel is present. Correct per MACK
procedures.
앫 Low engine oil level — Consult engine
manual for specifications. Add oil or
recalibrate dipstick as required.
앫 Worn rocker arm shaft bores or rocker
shaft — Inspect rocker arm shaft bores and
rocker shaft for wear. Repair as required.
앫 Worn main and/or rod bearings or
camshaft bushings — Inspect/measure
main bearings, rod bearings and cam
bushings in accordance with MACK
overhaul procedures. Replace as required.
ONE OR MORE CYLINDERS FAIL TO STOP
BRAKING OR ENGINE STALLS
앫 Control piston spring/valve inner spring
broken — Replace inner spring.
앫 One or more control pistons/valves stuck
in ON or UP position — Check control
pistons/valves for binding. Remove and
clean, or replace if necessary. Inspect lube
oil for contaminants.
앫 Solenoid valve sticking in ON position —
If solenoid valve cap remains down with no
electric current being supplied, replace the
solenoid valve.
앫 Center solenoid seal ring damaged
(allows oil to enter brake with solenoid
valve closed) — Remove solenoid and
replace all seal rings.
앫 Solenoid valve exhaust plugged —
Remove any restrictions at exhaust (bottom)
of solenoid valve.
앫 Clutch switch stuck in ON position or out
of adjustment — Check for proper
operation. Readjust or replace as needed.
ENGINE MISSES OR LOSES POWER
앫 Brake slave piston adjustment too
tight — Readjust brake slave piston
clearance in accordance with the table on
page 122.
SUDDEN DROP IN ENGINE LUBE OIL
PRESSURE
앫 Upper solenoid valve seal missing or
damaged — Remove solenoid and replace
upper seal ring.
5-111.bk Page 126 Monday, July 10, 2006 2:26 PM
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