ENGINE UNIT
EM-117
< UNIT DISASSEMBLY AND ASSEMBLY >
[VQ40DE]
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• If the measured value exceeds the limit, or if there are scratches
and/or seizure on the cylinder inner wall, hone or re-bore the inner
wall.
Piston Skirt Diameter
Measure the outer diameter of piston skirt with micrometer.
Piston to Cylinder Bore Clearance
Calculate by piston skirt diameter and cylinder bore inner diameter [direction (X), position (B)].
(Clearance) = (Cylinder bore inner diameter) – (Piston skirt diameter).
• If the calculated value exceeds the limit, replace piston and piston pin assembly. Refer to EM-124, "How to
Select Piston and Bearing".
Re-boring Cylinder Bore
1. Cylinder bore size is determined by adding piston to cylinder bore clearance to piston skirt diameter.
2. Install lower cylinder block, and tighten to the specified torque. Otherwise, cylinder bores may be distorted
in final assembly.
3. Cut cylinder bores.
NOTE:
• When any cylinder needs boring, all other cylinders must also be bored.
• Do not cut too much out of cylinder bore at a time. Cut only 0.05 mm (0.0020 in) or so in diameter at a
time.
4. Hone cylinders to obtain the specified piston to cylinder bore clearance.
5. Measure finished the cylinder bore for out-of-round and taper.
NOTE:
Measurement should be done after cylinder bore cools down.
CRANKSHAFT MAIN JOURNAL DIAMETER
• Measure the outer diameter of crankshaft main journals with micrometer.
SEM843E
Measure point
: Distance from the top 43.03 mm (1.6941 in)
Standard
: 95.480 - 95.510 mm (3.7590 - 3.7602 in)
PBIC2956E
Standard : 0.010 - 0.030 mm (0.0004 - 0.0012 in)
Limit : 0.08 mm (0.0031 in)
Re-bored size calculation: D = A + B – C
where,
D: Bored diameter
A: Piston skirt diameter as measured
B: Piston to cylinder bore clearance (standard value)
C: Honing allowance 0.02 mm (0.0008 in)
Revision: January 2013 2013 Xterra
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