Doosan G643 - Connecting Rod Bearings; Crankshaft End Play; Crankshaft Runout

G643 (E) Service Manual Chapter 3. Engine Mechanical System 93
Crankshaft Runout
Figure 12-64
Measure
Tool Required:
J 7872 Magnetic Base Dial Indicator
1. Crankshaft run-out.
A. Mount the crankshaft in V-blocks at crankshaft
journals 1 and 4.
B. Use a dial indicator as shown (figure 12-64).
C. If the main journals are misaligned, the
crankshaft is bent and must be replaced. The
main bearings must also be replaced at the
same time.
D. Grind or replace the crankshaft if necessary.
In general, the lower inserts (except the # 1
bearing) show the greatest wear and distress
from fatigue. Upon inspection, if a lower insert
is suitable for reuse, it can be assumed that
the upper insert is also satisfactory. If a lower
insert shows evidence of wear or damage,
both the upper and lower inserts must be
replaced.
Figure 12-64 Measuring Crankshaft Runout
Crankshaft End Play
Figure 12-65
Measure
• Crankshaft end play as follows:
a. Install crankshaft bearings, crankshaft, caps,
and bolts.
b. Tighten bolts to specification.
c. Firmly thrust end of the crankshaft first
rearward then forward. This will line up the
rear main bearing and crankshaft thrust
surfaces.
d. With the crankshaft wedged forward, measure
at the front end of the rear main bearing with a
feeler gage (figure 12-65). Refer to
“Specifications”.
IMPORTANT: If correct end play cannot be
obtained, be certain that the correct size rear
main bearing has been installed. Some
production engines may use crankshaft
bearings that are wider across the thrust faces
than standard size bearings. Refer to
“Specifications” for available bearing sizes.
Inspect
• Crankshaft for binding. Turn crankshaft to check
for binding. If the crankshaft does not turn freely,
loosen the crankshaft bearing bolts, one pair at a
time until the tight bearing is located. Burrs on the
bearing cap, foreign matter between the bearing
and the block or the bearing cap, or a faulty
bearing could cause a lack of clearance at the
bearing.
Figure 12-65 Measuring Crankshaft End Play
Connecting Rod Bearings
Follow all procedures outlined for crankshaft bearing
cleaning, inspection, and measurement. Refer to
“Specifications”.