REPAIR INSTRUCTIONS, PART 3
Page 457
It is mandatory that the T-handle torque
screwdriver (tool No. J 29919) be used to adjust
the MACK PowerLeash™ engine brake hydraulic
actuator.
The engine brake hydraulic actuator must be
adjusted prior to adjusting the exhaust valve lash.
1. Loosen the engine brake adjusting screw
(located above the push rod) locknut and
back the adjusting screw out several turns.
2. Loosen the swivel-head adjusting screw
locknut (located on the valve actuating side
of the exhaust rocker arm) and back the
adjusting screw out a couple of turns.
569
Figure 569 — Loosening Swivel-Head Adjusting Screw
3. Push down on the push rod end of the
exhaust rocker arm to fully depress the push
rod spring, then insert a 0.045-inch
(1.14 mm) thickness gauge between the
hydraulic actuator plunger and the actuator
pin located above the inboard exhaust valve.
570
Figure 570 — Inserting Thickness Gauge Between Brake
Plunger and Actuator Pin
It is recommended that a dull knife-edge be
ground onto the leading edge of the 0.045-inch
(1.14 mm) thickness gauge to facilitate inserting it
between the brake plunger and the actuator pin.
Doing this will eliminate the need for backing off
the adjusting screw to insert the thickness gauge.
A relief is cut in the lower surface of the rocker
arm to provide clearance for inserting the
thickness gauge. The thickness gauge must be
installed from the side of the rocker arm that
faces the rear of the engine, and at the angle
shown in the previous illustration.
4. Using the T-handle torque screwdriver (tool
No. J 29919), slowly turn the actuator
adjusting screw clockwise. As the
screwdriver is being turned, the push rod
spring will be compressed. Continue
tightening the adjusting screw until the
screwdriver clicks. At the point that the
screwdriver clicks, the push rod spring seats
are in contact and the push rod is solid. At
that point, hydraulic actuator lash is properly
set. Do not tighten the screwdriver any
further.
5-111.bk Page 457 Monday, July 10, 2006 2:26 PM
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