REPAIR INSTRUCTIONS, PART 1
Page 325
MACK PowerLeash™ Exhaust Valve Yoke
The PowerLeash™ exhaust yokes are different
from either the J-Tech™ and the non-brake
yokes in that they contain a hole for the exhaust
valve actuating pin. The actuating pin rests on a
cap that is installed over the tip of the valve stem
on the inboard exhaust valve.
379
Figure 379 — Valve Yoke Side View
INSTALLATION PROCEDURE
Make sure the correct yokes are used. If an
incorrect valve yoke from an earlier engine model
is used, the valve keepers will dislodge and
cause a dropped valve, resulting in severe engine
damage. If an incorrect valve yoke is used on a
J-Tech™ brake-equipped engine, the yoke will
disengage from the valve stem tip during engine
brake operation.
Used yokes have established wear patterns.
Yokes being returned to service should be
installed in the same position from which they
were removed.
Refer to Figure 381 for non-brake installations.
Although the valve yoke configuration is different,
the following installation procedure applies for
both non-brake and brake-equipped engines.
1. Lubricate the tips of the exhaust valve stems
with a small drop of clean engine oil.
2. For MACK PowerLeash™ engine
brake-equipped engines, install the valve
stem cap on the tip of the inboard exhaust
valve stem.
380
Figure 380 — Installing Valve Stem Cap
3. Lubricate the yoke guide pins (if equipped)
with clean engine oil.
1. Yoke, Exhaust Valve
2. Actuating Pin
3. Cap, Inboard Exhaust
Valve Stem Tip
1. Cap 2. Inboard Exhaust Valve
5-111.bk Page 325 Monday, July 10, 2006 2:26 PM
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