Komatsu 140-3 Series Shop Manual page 323

DISASSEMBLY AND ASSEMBLY
Tightening bolts by plastic-region turn-
ing angle method
• The important bolts of 140E-3 Series engines
are tightened by the plastic-region turning angle
method. In this method, special bolts are used
and tightened to the load at which they start per-
manent deformation (plastic region). Accord-
ingly, accurate and high tilting force is obtained.
Generally, tightening torque of bolts is controlled.
It is difficult, however to control the tilting force
accurately because of the effects of the coeffi-
cient of friction.
• In the plastic-region turning angle method, tight-
ening of a bolt is controlled by its initial tighten-
ing torque and turning angle.
• Bolts of 140E-3 Series engine tightened by plas-
tic-region turning angle method
1) Cylinder head mounting bolt
2) Main cap mounting bolt
3) Connecting rod cap mounting bolt
4) Flywheel mounting bolt
5) Idler bolt
If the plastic-region turning angle method is ap-
plied, the tightened bolts have permanent strain.
Accordingly, the allowable number of using times
of each bolt is limited. Observe the following pre-
cautions.
1) Before tightening each bolt, measure its
stem length and make sure that the result is
less than the using limit. If the stem is
longer than the using limit, do not use it but
replace it.
2) If a bolt is tightened more than the specified
angle, remove it and measure its stem
length again.
3) Try to tighten each bolt to the standard
angle as accurately as possible.
Clean each part carefully, and check it for bruise,
flaw, cavity, etc. Make sure each oil or water
path is through.
140-3 SERIES
GENERAL DISASSEMBLY OF ENGINE
13-21