Service Precautions; General Description; Engine Cleanliness And Care; Engine Service - Isuzu AA-6HK1T Workshop Manual

6A–2 ENGINE MECHANICAL

Service Precautions

• Be sure to use the correct fastener in the proper
location. If a used fastener is replaced with a new one,
the new fastener must be identical to the previous
one.
• Some fasteners must always be replaced with new
ones following removal. These fasteners are specified
in this Manual.
• Some fasteners require thread locker or thread
sealant. These fasteners are specified in this Manual.
• Supplemental fastener coatings (paint, grease, or
corrosion inhibitor) affect fastener torque and
clamping force. They may damage the fastener. Do
not use them unless specifically called for.
• Tighten all fasteners to the specified torque. If there is
a tightening sequence, follow it exactly.

General Description

Engine Cleanliness and Care

An industrial engine is a combination of many machines
that have been honed and polished. Tolerances are
ths
measured in 1,000
inches).
When servicing engine assemblies and parts, care and
cleanliness are extremely important. Proper cleaning
and the protection of friction areas and delicate parts are
part of the service procedure.
• Apply engine oil to all friction areas during reassembly
to provide protection and lubrication when the engine
is started.
• When valve train components, pistons, piston rings,
connecting rods, connecting rod bearings, and
crankshaft bearings are removed, they must be
reinstalled to their original positions. To ensure this,
mark the parts at disassembly and store them neatly.
• Disconnect battery cables before working on the
engine. This prevents damage to wire harnesses and
other electrical parts.
• Engine cylinders are numbered 1-2-3-4-5-6 from the
front of the engine (crankshaft pulley) to the rear
(flywheel).
Engine Service (General information)
Read the following carefully to avoid engine damage
and ensure reliable engine performance and a long
service life.
• The 12-volt electrical system is capable of damaging
delicate electrical circuits. Be absolutely certain that
the ground cable is disconnected at the battery when
servicing the engine.
of millimeters (10,000
• After removing the intake air duct or air cleaner,
immediately cover the intake opening with a clean
cloth. This prevents the entry of foreign material
capable of causing serious engine damage.

Engine Components

The 6HK1 engine is a 4-cycle, 6-cylinder in-line, diesel
engine with direct fuel injection. Engine displacement is
7.79 liters (475 cubic inches).
The engine uses a gear-driven overhead camshaft
timing train.
The engine is quiet, economical, and durable.
Cylinder Head
The cross-flow cylinder head is constructed of cast iron.
The intake system is at the left side of the engine and the
exhaust system is at the right side. This configuration
reduces resistance in the two systems.
A laminated cylinder head gasket is used to minimize
fatigue. The head and gasket are secured to the block
using the angular tightening method. This provides a
reliable seal against gas and water leakage.
ths
Cylinder Block and Cylinder Liners
of
The cast iron cylinder block has 7 bearings. Bearing
caps have a ladder frame construction to integrate them
with the crankcase and increase engine rigidity.
Cylinder liners are constructed of very thin, special-use
iron alloys. In combination with the chrome-plated 1
rd
and 3 piston rings, they provide excellent wear
resistance.
Pistons
The aluminum alloy pistons have a ring trigger cast into
the 1st ring groove. The outer sliding surface of the 1
rd
and 3 piston rings are chrome plated to provide
strength and wear resistance.
Crankshaft
The forged steel crankshaft is soft nitride treated for
additional strength. The 7 bearings together with the 4
counterweights result in reduced bearing rotational load.
Gear Train
The gear train is at the rear of the engine (flywheel side).
This minimizes torsion vibration from the crankshaft and
reduces noise.
To further reduce noise, the crankshaft gear is shrink-
fitted to the crankshaft. Precise gear arrangement, gear
ratio, backlash, and bearing rigidity also contribute to a
quieter engine.
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