REPAIR INSTRUCTIONS
Page 293
Engine Brake Control Valve
Replacement
(J-Tech™ Engine Brake)
GENERAL INFORMATION
With J-Tech™ engine brake units built prior to
June 1999, the possibility exists that the snap ring
securing the control valve in the J-Tech™ brake
units may break or dislodge, allowing oil pressure
to push the control valve components from the
housing bore. This results in loss of oil pressure
and a poor performing or non-functioning engine
brake unit. In most instances, however, this
condition will go unnoticed until the cylinder head
covers are removed. A broken or dislodged
control valve retaining snap ring will not cause
any damage to the engine.
320
Figure 320 — Engine Brake Housing Assembly
To prevent breaking or dislodging of the control
valve snap ring, the J-Tech™ control valve
components have been redesigned to
incorporate a new-style collar (which replaces the
old-style valve stop spacer), an outer spring and
a retaining washer (Figure 321). With this
change, the part No. of the engine brake housing
assembly was changed from 757GB58B to
757GB58C (beginning with housing assembly
serial No. D690060001), and was phased into
E-Tech™ engine production June 30, 1999
(beginning with engine serial number 9M4395).
A control valve update kit (part No. 4559-28190)
for Jacobs 690 (J-Tech™) engine brake is
available through the MACK Parts System. The
kit includes all the necessary components to
replace all six control valves on the engine.
5_106_00.bk Page 293 Friday, August 4, 2000 11:17 AM
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