Isuzu N-Series. Manual — part 337

6A-90 ENGINE MECHANICAL

ENGINE (4HF1 / 4HF1-2 / 4HE1-TC / 4HG1 / 4HG1-T) 6A3-1

ENGINE 4H SERIES

SECTION 6A3

ENGINE

(4HF1 / 4HF1-2 / 4HE1-TC / 4HG1 / 4HG1-T)

Contents

GENERAL DESCRIPTION . . . . . . . . . 6A3-3

Cylinder Head. . . . . . . . . . . . .. 6A3-5
Cylinder Block. . . . . . . . . . . . .. 6A3-5
Piston, Connecting Rod and Crankshaft . . . 6A3-6
Valve Train . . . . . . . . . . . . . .. 6A3-7
Fuel System. . . . . . . . . . . . . . 6A3-8
Intake and Exhaust Systems . . . . . . ... 6A3-8
Lubrication System . . . . . . . . . . .. 6A3-9
Cooling System . . . . . . . . . . . ... 6A3-9
Important Operations. . . . . . . . . .6A3-10

ENGINE MOUNT (RH,LH) . . . . . . . . 6A3-11

Component . . . . . . . . . . . . . 6A3-11
Removal . . . . . . . . . . . . . . 6A3-11
Installation . . . . . . . . . . . . . .6A3-12

CYLINDER HEAD COVER . . . . . . . ...6A3-13

Component . . . . . . . . . . . . . 6A3-13
Removal . . . . . . . . . . . . . . 6A3-13
Installation . . . . . . . . . . . . . .6A3-13

INLET COVER / INLET CASE . . . . . . .. 6A3-15

Component . . . . . . . . . . . . . 6A3-15
Removal . . . . . . . . . . . . . . 6A3-15
Installation . . . . . . . . . . . . . .6A3-17

EXHAUST GAS RECIRCULATION SYSTEM (EGR). 6A3-21

Component . . . . . . . . . . . . . 6A3-21
Removal . . . . . . . . . . . . . . 6A3-21
Installation . . . . . . . . . . . . . .6A3-21

EXHAUST GAS RECIRCULATION SYSTEM (EGR). 6A3-24

Component . . . . . . . . . . . . . 6A3-24
Removal . . . . . . . . . . . . . . 6A3-24
Installation . . . . . . . . . . . . . .6A3-24

EXHAUST MANIFOLD. . . . . . . . . ..6A3-26

Component . . . . . . . . . . . . . 6A3-26
Removal . . . . . . . . . . . . . . 6A3-26
Installation . . . . . . . . . . . . . .6A3-27

TIMING GEAR REPLACEMENT . . . . . ..6A3-29

Component . . . . . . . . . . . . . 6A3-29
Removal . . . . . . . . . . . . . . 6A3-30
Inspection . . . . . . . . . . . . . ..6A3-34
Installation . . . . . . . . . . . . . .6A3-35

VALVE GUIDE SEAL & VALVE SPRING . . .6A3-40

Component . . . . . . . . . . . . . 6A3-40
Removal . . . . . . . . . . . . . . 6A3-40
Installation . . . . . . . . . . . . . .6A3-42

ROCKER ARM SHAFT ASSEMBLY. . . . .6A3-45

Component . . . . . . . . . . . . . 6A3-45
Removal . . . . . . . . . . . . . . 6A3-45
Installation . . . . . . . . . . . . . .6A3-46

CAMSHAFT ASSEMBLY . . . . . . . . ..6A3-48

Component . . . . . . . . . . . . . 6A3-48

Removal. . . . . . . . . . . . . . .6A3-48
Installation. . . . . . . . . . . . . ..6A3-49

CYLINDER HEAD . . . . . . . . . . . .6A3-51

Component . . . . . . . . . . . . . 6A3-51
Removal. . . . . . . . . . . . . . .6A3-53
Installation. . . . . . . . . . . . . ..6A3-55

CIRCUMFERENCE PARTS OF CYLINDER HEAD..6A3-61

Component . . . . . . . . . . . . . 6A3-61
Removal. . . . . . . . . . . . . . .6A3-61
Installation. . . . . . . . . . . . . ..6A3-62

OIL FILTER ASSEMBLY . . . . . . . . ...6A3-67

Component . . . . . . . . . . . . . 6A3-67
Removal. . . . . . . . . . . . . . .6A3-67
Inspection. . . . . . . . . . . . . ...6A3-67
Installation. . . . . . . . . . . . . ..6A3-67

OIL FILTER CARTRIDGE . . . . . . . . .6A3-69

Component . . . . . . . . . . . . . 6A3-69
Removal. . . . . . . . . . . . . . .6A3-69
Installation. . . . . . . . . . . . . ..6A3-69

OIL COOLER. . . . . . . . . . . . . .6A3-70

Component . . . . . . . . . . . . . 6A3-70
Removal. . . . . . . . . . . . . . .6A3-71
Disassembly. . . . . . . . . . . . ...6A3-73
Reassembly . . . . . . . . . . . . ...6A3-73
Installation. . . . . . . . . . . . . ..6A3-74

OIL PAN . . . . . . . . . . . . . . . 6A3-79

Component . . . . . . . . . . . . . 6A3-79
Removal. . . . . . . . . . . . . . .6A3-79
Installation. . . . . . . . . . . . . ..6A3-79

OIL PUMP ASSEMBLY . . . . . . . . . .6A3-82

Component . . . . . . . . . . . . . 6A3-82
Removal. . . . . . . . . . . . . . .6A3-83
Installation. . . . . . . . . . . . . ..6A3-84

OIL RELIEF VALVE. . . . . . . . . . ...6A3-87

Removal. . . . . . . . . . . . . . .6A3-87
Inspection and Repair . . . . . . . . . 6A3-87
Installation. . . . . . . . . . . . . ..6A3-87

PISTON, PISTON RING, PISTON PIN AND CONNECTING
ROD . . . . . . . . . . . . . . . . ...6A3-88

Component . . . . . . . . . . . . . 6A3-88
Removal. . . . . . . . . . . . . . .6A3-88
Installation. . . . . . . . . . . . . ..6A3-90

FLYWHEEL AND PILOT BEARING . . . . ..6A3-93

Component . . . . . . . . . . . . . 6A3-93
Removal. . . . . . . . . . . . . . .6A3-93
Inspection and Repair . . . . . . . . . 6A3-95
Installation. . . . . . . . . . . . . ..6A3-96

CRANKSHAFT FRONT OIL SEAL. . . . . 6A3-98

Component . . . . . . . . . . . . . 6A3-98

6A3-2 ENGINE (4HF1 / 4HF1-2 / 4HE1-TC / 4HG1 / 4HG1-T)

Removal . . . . . . . . . . . . . . 6A3-98
Installation . . . . . . . . . . . . ... 6A3-100

CRANKSHAFT REAR OIL SEAL. . . . . 6A3-104

Component . . . . . . . . . . . . .. 6A3-104
Removal . . . . . . . . . . . . . .. 6A3-104
Installation . . . . . . . . . . . . ... 6A3-105

CRANKSHAFT. . . . . . . . . . . . 6A3-108

Component . . . . . . . . . . . . .. 6A3-108
Removal . . . . . . . . . . . . . .. 6A3-109
Installation . . . . . . . . . . . . ... 6A3-114

CYLINDER BLOCK. . . . . . . . . . . 6A3-122

Component . . . . . . . . . . . . .. 6A3-122
Removal . . . . . . . . . . . . . .. 6A3-123
Installation . . . . . . . . . . . . ... 6A3-130

ENGINE ASSEMBLY . . . . . . . . . .. 6A3-146

Component . . . . . . . . . . . . .. 6A3-146
Removal . . . . . . . . . . . . . .. 6A3-150
Installation . . . . . . . . . . . . ... 6A3-152

ENGINE (4HF1 / 4HF1-2 / 4HE1-TC / 4HG1 / 4HG1-T) 6A3-3

GENERAL DESCRIPTION

The engine is a four-cycle, four-cylinder, in-line, direct
fuel injection type diesel engine with the piston displace-
ment of 4,334 cc. It features a gear driven OHC (over-
head camshaft) timing train and the unique mechanisms
and systems designed for outstanding cleanness, econ-
omy and durability. Its torque characteristics promise
dynamic ride at high speed, high power at low speed,
and smooth and continuous torque at medium to high
ranges.
For 4HF1

For 4HF1

For 4HG1-T

For 4HG1-T

N6A0358E

N6A0359E

N6A0360E

N6A0361E