Jeep XJ. Manual — part 298
SPECIAL TOOLS
2.5L ENGINE SPECIAL TOOLS
Valve Spring Compressor Tool MD-998772A
Timing Case Cover Alignment and Seal installation
Tool 6139
Vibration Damper Removal Tool 7697
Rear Main Seal Installer Tool 6271A
Hydraulic Valve Tappet Removal/Installation Tool
C-4129–A
9 - 60
2.5L ENGINE
XJ
4.0L ENGINE
TABLE OF CONTENTS
page
page
DESCRIPTION AND OPERATION
ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
LUBRICATION SYSTEM . . . . . . . . . . . . . . . . . . . . 62
CYLINDER BLOCK. . . . . . . . . . . . . . . . . . . . . . . . 65
CYLINDER HEAD. . . . . . . . . . . . . . . . . . . . . . . . . 65
CRANKSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
PISTON AND CONNECTING ROD . . . . . . . . . . . . 66
CAMSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
ROCKER ARM . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
VALVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
VALVE SPRING . . . . . . . . . . . . . . . . . . . . . . . . . . 67
CYLINDER HEAD COVER . . . . . . . . . . . . . . . . . . 67
HYDRAULIC TAPPET . . . . . . . . . . . . . . . . . . . . . . 67
VALVE GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
OIL PAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
VALVE STEM SEAL . . . . . . . . . . . . . . . . . . . . . . . 67
INTAKE MANIFOLD . . . . . . . . . . . . . . . . . . . . . . . 67
EXHAUST MANIFOLD . . . . . . . . . . . . . . . . . . . . . 68
DIAGNOSIS AND TESTING
ENGINE DIAGNOSIS—INTRODUCTION. . . . . . . . 68
SERVICE DIAGNOSIS—PERFORMANCE . . . . . . 69
SERVICE DIAGNOSIS—MECHANICAL. . . . . . . . . 70
INTAKE MANIFOLD LEAKAGE DIAGNOSIS . . . . . 72
CYLINDER COMPRESSION PRESSURE TEST . . 73
ENGINE CYLINDER HEAD GASKET FAILURE
DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
LEAKAGE TEST . . . . . . . . . . . . . . . . . . . . . . . . 73
ENGINE OIL LEAK INSPECTION . . . . . . . . . . . . . 74
ENGINE OIL PRESSURE . . . . . . . . . . . . . . . . . . . 75
SERVICE PROCEDURES
VALVE TIMING . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
VALVE SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . 75
PISTON FITTING . . . . . . . . . . . . . . . . . . . . . . . . . 77
PISTON RING—FITTING . . . . . . . . . . . . . . . . . . . 77
FITTING CONNECTING ROD BEARINGS. . . . . . . 80
FITTING CRANKSHAFT MAIN BEARINGS . . . . . . 83
FORM-IN-PLACE GASKETS. . . . . . . . . . . . . . . . . 86
ENGINE PERFORMANCE . . . . . . . . . . . . . . . . . . 87
HONING CYLINDER BORES . . . . . . . . . . . . . . . . 87
REPAIR DAMAGED OR WORN THREADS . . . . . . 88
SERVICE ENGINE ASSEMBLY (SHORT
BLOCK). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
REMOVAL AND INSTALLATION
ENGINE MOUNTS—FRONT. . . . . . . . . . . . . . . . . 90
ENGINE MOUNT—REAR . . . . . . . . . . . . . . . . . . . 91
ENGINE ASSEMBLY. . . . . . . . . . . . . . . . . . . . . . . 92
INTAKE AND EXHAUST MANIFOLD . . . . . . . . . . . 95
EXHAUST MANIFOLD—4.0L ENGINE . . . . . . . . . 96
CYLINDER HEAD COVER . . . . . . . . . . . . . . . . . . 96
ROCKER ARMS AND PUSH RODS . . . . . . . . . . . 96
VALVE SPRINGS AND OIL SEALS . . . . . . . . . . . . 97
CYLINDER HEAD. . . . . . . . . . . . . . . . . . . . . . . . . 98
VALVES AND VALVE SPRINGS . . . . . . . . . . . . . 100
HYDRAULIC TAPPETS . . . . . . . . . . . . . . . . . . . . 100
VIBRATION DAMPER . . . . . . . . . . . . . . . . . . . . . 101
TIMING CASE COVER . . . . . . . . . . . . . . . . . . . . 101
TIMING CHAIN AND SPROCKETS . . . . . . . . . . . 102
CAMSHAFT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
CAMSHAFT BEARINGS . . . . . . . . . . . . . . . . . . . 104
CRANKSHAFT MAIN BEARINGS . . . . . . . . . . . . 105
OIL PAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
PISTONS AND CONNECTING RODS . . . . . . . . . 108
CRANKSHAFT OIL SEALS—REAR . . . . . . . . . . . 110
OIL PUMP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
TIMING CASE COVER OIL SEAL . . . . . . . . . . . . 112
DISASSEMBLY AND ASSEMBLY
CYLINDER BLOCK . . . . . . . . . . . . . . . . . . . . . . . 112
CLEANING AND INSPECTION
CYLINDER HEAD . . . . . . . . . . . . . . . . . . . . . . . . 113
CYLINDER HEAD COVER . . . . . . . . . . . . . . . . . 113
ROCKER ARMS AND PUSH RODS . . . . . . . . . . 113
HYDRAULIC TAPPETS . . . . . . . . . . . . . . . . . . . . 113
CYLINDER BLOCK . . . . . . . . . . . . . . . . . . . . . . . 114
SPECIFICATIONS
SPECIFICATIONS. . . . . . . . . . . . . . . . . . . . . . . . 115
TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . . 118
SPECIAL TOOLS
4.0L ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
XJ
4.0L ENGINE
9 - 61
DESCRIPTION AND OPERATION
ENGINE
DESCRIPTION
The 4.0 Liter (242 CID) six-cylinder engine is an
In-line, lightweight, overhead valve engine.
This engine is designed for unleaded fuel. The
engine cylinder head has dual quench-type combus-
tion chambers that create turbulence and fast burn-
ing of the air/fuel mixture. This results in good fuel
economy.
The cylinders are numbered 1 through 6 from front
to rear. The firing order is 1-5-3-6-2-4 (Fig. 1).
The crankshaft rotation is clockwise, when viewed
from the front of the engine. The crankshaft rotates
within seven main bearings. The camshaft rotates
within four bearings.
BUILD DATE CODE
The engine Build Date Code is located on a
machined surface on the right side of the cylinder
block between the No.2 and No.3 cylinders (Fig. 2).
The digits of the code identify:
• 1st Digit—The year (8 = 1998).
• 2nd & 3rd Digits—The month (01 - 12).
• 4th & 5th Digits—The engine type/fuel system/
compression ratio (MX = A 4.0 Liter (242 CID) 8.7:1
compression ratio engine with a multi-point fuel
injection system).
• 6th & 7th Digits—The day of engine build (01 -
31).
(1)
FOR EXAMPLE: Code * 801MX12 * identi-
fies a 4.0 Liter (242 CID) engine with a multi-point
fuel injection system, 8.7:1 compression ratio and
built on January 12, 1998.
LUBRICATION SYSTEM
DESCRIPTION
A
gear—type
positive
displacement
pump
is
mounted at the underside of the block opposite the
No. 4 main bearing.
OPERATION
The pump draws oil through the screen and inlet
tube from the sump at the rear of the oil pan. The oil
is driven between the drive and idler gears and
pump body, then forced through the outlet to the
block. An oil gallery in the block channels the oil to
the inlet side of the full flow oil filter. After passing
through the filter element, the oil passes from the
center outlet of the filter through an oil gallery that
channels the oil up to the main gallery which
extends the entire length of the block.
Galleries extend downward from the main oil gal-
lery to the upper shell of each main bearing. The
crankshaft is drilled internally to pass oil from the
main bearing journals (except number 4 main bear-
ing journal) to the connecting rod journals. Each con-
necting rod bearing cap has a small squirt hole, oil
passes through the squirt hole and is thrown off as
the rod rotates. This oil throwoff lubricates the cam-
shaft lobes, distributor drive gear, cylinder walls, and
piston pins.
The hydraulic valve tappets receive oil directly
from the main oil gallery. Oil is provided to the cam-
shaft bearing through galleries. The front camshaft
bearing journal passes oil through the camshaft
Fig. 1 Engine Firing Order
Fig. 2 Build Date Code Location
1 – YEAR
2 – MONTH
3 – DAY
9 - 62
4.0L ENGINE
XJ
sprocket to the timing chain. Oil drains back to the
oil pan under the number one main bearing cap.
The oil supply for the rocker arms and bridged
pivot assemblies is provided by the hydraulic valve
tappets which pass oil through hollow push rods to a
hole in the corresponding rocker arm. Oil from the
rocker arm lubricates the valve train components,
then passes down through the push rod guide holes
in the cylinder head past the valve tappet area, and
returns to the oil pan.
XJ
4.0L ENGINE
9 - 63
DESCRIPTION AND OPERATION (Continued)
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст