Page 116
TROUBLESHOOTING
앫 Solenoid not fully seated in rocker shaft
bore — Remove the solenoid, inspect and
replace the O-rings as required. Reinstall
the solenoid to its full seated position before
snapping the retaining spring clips in place.
The clips must require a moderate force to
snap them around the rocker shaft and must
provide enough spring tension to prevent
any free movement of the solenoid or spring
clips. If spring clip tension cannot be
maintained, replace the clips.
ENGINE BRAKE SLOW TO OPERATE OR
WEAK IN EFFECT
앫 Improper brake piston adjustment —
Readjust in accordance with the table on
page 114.
앫 Hydraulic lash adjuster plunger not
moving in bore — Inspect engine brake
hydraulic actuator plunger for freedom of
movement in the bore. Spring pressure
should keep the plunger seated against the
lower snap ring. If plunger does not move
freely, replace the rocker arm assembly.
앫 Control piston binding in rocker arm
bores — Remove control piston. Make sure
check ball is seated in bore and can be
moved off seat. Make sure there is spring
pressure against the ball. Flush the ball
check valve in a suitable, non-flammable
cleaning solvent. If the ball check valve does
not function properly, replace the rocker
assembly.
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 113.
Disconnect the solenoid lead and provide
12 volts directly to the solenoid.
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 solenoid and inspect
O-ring; replace if missing or damaged.
앫 Plugged or damaged oil supply screen —
Remove the rocker shaft assembly and
inspect the oil supply screen located in the
oil supply port of the number one and four
rocker shaft mounting brackets. Clean and
replace as required.
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.
5-111.bk Page 116 Monday, July 10, 2006 2:26 PM
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