Page 172
REPAIR INSTRUCTIONS, PART 1
ENGINES WITHOUT ENGINE BRAKE OR
WITH MACK POWERLEASH™ ENGINE
BRAKE
For engines without an engine brake and those
equipped with the MACK PowerLeash™ engine
brake, remove the rocker arms, valve yokes and
push rods as follows:
1. Remove the six capscrews and washers
retaining the rocker arm assembly to each
cylinder head.
2. If the engine is equipped with a MACK
PowerLeash™ engine brake, disconnect the
ground and power wires.
166
Figure 166 — Engine Brake Solenoid Ground Wire
Secured to Cylinder Head Bolt
3. Remove the rocker arm assemblies from
each cylinder head.
4. Remove the valve yokes from each pair of
valves by lifting straight up on each yoke.
Tag the yokes for reassembly in the same
location.
5. Remove the valve push rods and tag the
rods for reassembly.
Revised Rocker Arm Shift Mounting
Bolts
Effective November 16, 2005, a revised rocker
shaft mounting bolt (part No. 416GC23M) was
implemented into production on all ASET™
engines, replacing the previously used bolt (part
No. 65AM5010). These bolts are available
through the MACK Parts System, and should be
used for any replacement needs for ASET™
engines.
If any rocker shaft mounting bolts are found to be
broken, all 12 mounting bolts MUST be replaced.
If loose or broken rocker shaft mounting bolts are
encountered at disassembly, or if the rocker shaft
is bent, contingent damage must be inspected
and repaired as follows:
앫 Any type of valve train failure that results in
excessive valve lash will generally result in a
cracked or broken ceramic roller lifter. At any
cylinder where the rocker shaft mounting
bolts are loose or broken, or if the rocker
shaft is bent, the oil pan must be removed
and the engine rotated so that the cam lobe
at the affected cylinder is pointed down.
Inspect the lifter rollers at that location for
obvious signs of roller damage. Also inspect
the cam lobe for damage. Replace
components as required. Additionally, if
replacement of any of the lifters is required,
the H-rings at the replaced lifter locations
must be inspected for partial or full
dislodgement and replaced as required.
If obvious signs of damage to ceramic rollers
are not evident and the lifters were not
replaced, the vehicle must be driven on a
short road test (for at least 1/2 hour) before
being returned to service.
앫 Loose or broken rocker shaft mounting bolts
will allow the rocker shaft to flex and
eventually break. The rocker shaft may be
cracked and must be replaced if the
mounting bolts are loose or broken.
앫 If the rocker shaft is broken, the lifters must
be replaced at the affected cylinder(s), and
the H-rings must be inspected for partial or
full dislodgement and replaced as required.
1. Ground Wire Location
5-111.bk Page 172 Monday, July 10, 2006 2:26 PM
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