Mack MP7 - Rocker Arm, Check

TROUBLESHOOTING
Page 79
5. Increase the pressure to 250 kPa (35 psi)
using the reduction valve knob and check for
air bubbles emerging from the oil cooler. The
test period should last for at least one
minute.
Air bubbles emerging from the oil cooler indicate
a leak. The oil cooler should be replaced.
Rocker Arm, Check
Make sure there is clearance between the rocker
arm rollers and the camshaft when performing
the following rocker arm bushing and roller
bushing checks.
ROCKER ARM BUSHINGS
1. Install the appropriate flywheel turning tool,
9996956 (MP7) or 88800014 (MP8 and
MP10), and turn the engine until the
camshaft is in a position where the rocker
arm roller being checked is on the base
circle of the camshaft lobe. Make sure that
there is clearance between the roller and
camshaft.
To check the injector, the rocker arm roller must
be on the base circle of the camshaft lobe and
the injector adjusting screw backed off (preload
must be readjusted).
2. Position the magnetic stand, 9999696, and
dial indicator, 9989876, so that the tip of the
indicator is on top of the rocker arm above
the middle of the rocker arm shaft bushing
area.
68
Figure 68 — Dial Indicator Positioning (Typical Rocker
Component Shown)
3. Push down on the rocker arm so that any oil
film is forced out of the upper side of the
rocker arm shaft.
4. Set the dial indicator to zero.
5. Position a pry bar directly under the rocker
arm in the shaft area. Pry the rocker arm up
and note the reading on the dial indicator.
The maximum clearance allowed between
the rocker arm and shaft is 0.1 mm
(0.0039 inch). If the clearance is greater,
replace the rocker arm and check the shaft
for wear.
69
Figure 69 — Prying Rocker Arm Up (Typical Rocker
Component Shown)