Caterpillar Cat 621G Wheel Tractor (Prefix CEN) Service Repair Manual Instant Download.pdf

Service Repair Manual
Models
621G Wheel Tractor

Shutdown SIS
Previous Screen
Product: WHEEL TRACTOR
Model: 621G WHEEL TRACTOR CEN
Configuration: 621G Wheel Tractor CEN00001-UP (MACHINE) POWERED BY 3406E Engine
Disassembly and Assembly
3406E and 3456 Engines for Caterpillar Built Machines
Media Number -RENR1364-06 Publication Date -01/05/2008 Date Updated -20/05/2008
i02489840
Cylinder Head - Remove
SMCS - 1100-011
Removal Procedure
Start By:
A. Remove the water temperature regulator. Refer to Disassembly and Assembly, "Water
Temperature Regulator - Remove and Install".
B. Remove the exhaust manifold. Refer to Disassembly and Assembly, "Exhaust Manifold -
Remove and Install".
C. Remove the valve mechanism cover base. Refer to Disassembly and Assembly, "Valve
Mechanism Cover Base - Remove and Install".
D. Remove the electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit
Injector - Remove".
E. Remove the camshaft gear. Refer to Disassembly and Assembly, "Camshaft Gear - Remove
and Install".
NOTICE
Keep all parts clean from contaminants.
Contaminants may cause rapid wear and shortened component life.
NOTICE
Care must be taken to ensure that fluids are contained during
performance of inspection, maintenance, testing, adjusting and repair
of the product. Be prepared to collect the fluid with suitable containers
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https://127.0.0.1/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/siswe...

before opening any compartment or disassembling any component
containing fluids.
Refer to Special Publication, NENG2500, "Caterpillar Dealer Service
Tool Catalog" for tools and supplies suitable to collect and contain
fluids on Caterpillar products.
Dispose of all fluids according to local regulations and mandates.
Illustration 1 g01028806
NOTICE
Do not turn the crankshaft or the camshaft while the camshaft gear is
removed. If the front gear group is not correctly timed during
installation, interference can occur between the pistons and the valves,
resulting in damage to the engine.
1. Remove bolts (2) and thrust plate (1) .
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2. Remove seal assembly (3) and adapter (4) .
3. Remove O-ring seals (5) and (6) from seal assembly (3) .
4. Disconnect hose assembly (7) from cylinder head (8) .
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Note: If the engine is not equipped with an air compressor, skip Step 5.
5. Disconnect hose assemblies (11) and hose assemblies (12) from the air compressor.
6. Remove the bolt and clamp (9) from the hose assembly. Remove hose assembly (10) .
7. Remove the bolt and support clip (13) for the harness assembly.
8. Disconnect the harness assembly from sensor (14) , sensor (15) , and ground stud (16) .
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9. Remove bolts (18) and spacers (17) that fasten bracket (19) to the cylinder head.
10. Remove cylinder head bolts (20) .
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11. Attach a suitable lifting device to cylinder head (8) . Ensure that all of the following items
are clear from the cylinder head: harness assemblies, tube assemblies and hose assemblies.
12. Carefully remove cylinder head (8) . The weight of the cylinder head is approximately 235
kg (518 lb).
13. Remove cylinder head gasket (21) .
14. Remove O-ring seal (22) and water seals (23) . Remove seal (24) .
15. Remove the spacer plate from the engine.
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16. Remove spacer plate gasket (25) .
17. Remove O-ring seal (26) .
Note: If the cylinder head was removed from the cylinder block as a result of a failed head gasket,
refer to Special Instruction, SEHS9564, "3400 Cylinder Head Joint Repair Procedure" for
additional information.
Copyright 1993 - 2021 Caterpillar Inc.
All Rights Reserved.
Private Network For SIS Licensees.
Sun Mar 7 16:00:19 UTC+0800 2021
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Shutdown SIS
Previous Screen
i07498909
Cylinder Head - Install
SMCS - 1100-012
Installation Procedure
Table 1
Required Tools
Tool Part Number Part Description Qty
A - Loctite Graphite 50 Anti-Seize -
B 8T-2998 Lubricant 1
C 9S-3263 Thread Lock Compound 1
NOTICE
Note: Thoroughly clean the spacer plate and the bottom surface of the cylinder head. A new spacer plate
gasket must be installed when the cylinder head is removed.
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1. Apply a thin film of clean engine oil to O-ring seal (26). Install O-ring seal (26).
2. Install a new spacer plate gasket (25).
3. Install the spacer plate on the engine.
4. Apply a thin film of clean engine oil to O-ring seal (22). Install O-ring seal (22).
5. Install water seals (23) dry.
6. Install seal (24) in the spacer plate.
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7. Install a new cylinder head gasket (21).
8. Attach a suitable lifting device to cylinder head (8). Carefully position cylinder head (8) on the
spacer plate. The weight of the cylinder head is approximately 235 kg (518 lb).
Note: The bolts that are Marked “X” are 216 mm (8.5 inch) long. The remainders of the bolts are
194 mm (7.6 inch) in length.
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9. Apply a small amount of Tooling (A) to the bolt threads and both sides of the washers. Install the
cylinder head bolts. Tighten the cylinder head bolts, as follows.
a. In a numerical sequence, tighten bolts 1 through 26 to a torque of 270 ± 15 N·m
(200 ± 11 lb ft).
b. In a numerical sequence, tighten bolts 1 through 26 to a torque of 450 ± 15 N·m
(330 ± 11 lb ft).
c. In a numerical sequence, again tighten bolts 1 through 26 to a torque of 450 ± 15 N·m
(330 ± 11 lb ft).
10. Install spacers (17) and bolts (18) that fasten bracket (19) to the cylinder head.
11. Connect the harness assembly to sensor (14), sensor (15), and ground stud (16).
12. Install the bolt and support clip (13) for the harness assembly.
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13. Install hose assemblies (10). Install the bolt and clamp (9).
Note: If the engine is not equipped with an air compressor, skip Step 14.
14. Connect hose assemblies (11) and hose assemblies (12) to the air compressor.
15. Connect hose assembly (7) to cylinder head (8).
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16. Install O-ring seals (5) and (6) in seal assembly (3). Lubricate seal (6) with Tooling (B).
17. Assemble thrust plate (1) and seal assembly (3). Apply Tooling (C) to bolts (2). Hold the assembly in
position and install bolts (2). Evenly tighten bolts (2) until seal assembly (3) and O-ring seal (5) are
seated against the cylinder head.
Note: Be careful to ensure that O-ring seal (5) stays in the groove in seal assembly (3).
18. Install adapter (4). Ensure that the dowel in adapter (4) engages the hole in the camshaft.
End By:
a. Install the camshaft gear. Refer to Disassembly and Assembly, "Camshaft Gear - Remove and
Install".
b. Install the electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector -
Install".
c. Install the valve mechanism cover base. Refer to Disassembly and Assembly, "Valve Mechanism
Cover Base - Remove and Install".
d. Install the exhaust manifold. Refer to Disassembly and Assembly, "Exhaust Manifold - Remove and
Install".
e. Install the water temperature regulator. Refer to Disassembly and Assembly, "Water Temperature
Regulator - Remove and Install".
Sun Mar 7 16:01:14 UTC+0800 2021
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Shutdown SIS
Previous Screen
i02110801
Camshaft - Remove
SMCS - 1210-011
Removal Procedure
Table 1
Required Tools
A 9U-7257 Cradle 1
B 9U-7256 Guide 1
C 9U-7225 Camshaft Pilot 2
D 9U-7240 Camshaft Hook 2
Start By:
A. Remove the camshaft gear. Refer to Disassembly and Assembly, "Camshaft Gear - Remove
and Install".
B. Remove the rocker arms and the rocker shafts. Refer to Disassembly and Assembly,
"Rocker Arm and Shaft - Remove".
NOTICE
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NOTICE
containing fluids.
Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop
Products Guide" for tools and supplies suitable to collect and contain
NOTICE
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NOTICE
Care must be used when removing the camshaft to not damage the
highly finshed surfaces of both the camshaft and camshaft bearings
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4. Use the bolts for the rocker arm shaft assembly to install Tooling (A) at Location (Y) .
5. Install Tooling (B) on front housing (7). Do not tighten the bolts for Tooling (B) at this
time.
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Note: It is necessary to install Tooling (C) on the camshaft. Tooling (C) will support the
rear of camshaft (8) as the camshaft is moved out of the cylinder head and into Tooling (B) .
6. Move camshaft (8) forward and install one Tooling (C) in the end of camshaft (8). Again,
move the camshaft forward and install remaining Tooling (C) into the back of first Tooling
(C) .
7. Position camshaft (8) into the bore of Tooling (B). Tighten the bolts that hold Tooling (B) to
the front housing.
Note: Avoid lifting camshaft (8) with Tooling (D). The camshaft should rest on Tooling
(A). Lifting of the camshaft can cause misalignment as the camshaft is removed, resulting in
damage to the camshaft bearings.
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8. Remove camshaft (8), as follows:
a. Use Tooling (D) to move camshaft (8) toward the front of the engine. Reposition
Tooling (D), as needed.
b. Move camshaft (8) far enough out of the cylinder head in order to attach a suitable
lifting device.
c. Keep the camshaft level while the camshaft is being removed from the cylinder head.
The weight of the camshaft is approximately 39 kg (86 lb).
Alternative Removal Procedure
Table 2
Required Tools
E (1)
177-8001 Sleeve 1
F 177-8002 Adapter 1
G 6L-4697 Bolts 3
( 1 )
Part of 177-8003 Engine Tool Group
Start By:
A. Remove the camshaft gear. Refer to Disassembly and Assembly, "Camshaft Gear - Remove
and Install".
B. Remove the rocker arms and the rocker shafts. Refer to Disassembly and Assembly,
"Rocker Arm and Shaft - Remove".
Note: This is an optional procedure to remove the camshaft. The preceding tool list shows the
required tooling for removing the camshaft from the front of the engine or the rear of the engine.
NOTICE
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NOTICE
containing fluids.
Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop
Products Guide" for tools and supplies suitable to collect and contain
NOTICE
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4. Remove screws (7) and cover (8) .
NOTICE
Care must be used when removing the camshaft to not damage the
highly finshed surfaces of both the camshaft and camshaft bearings
Note: Carefully align Tooling (F) with the end of the camshaft. If the adapter and the
camshaft are not aligned, the camshaft may not be removed. The adapter and camshaft
bearing will interfere.
5. To remove the camshaft from the rear of the engine, install Tooling (F) on the front of the
camshaft with Tooling (G) .
6. Install Tooling (E) .
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7. Carefully slide the camshaft to the rear of the engine for removal. Use two technicians to
remove the camshaft. Keep the camshaft level while the camshaft is being removed from
the cylinder head. The weight of the camshaft is approximately 39 kg (86 lb).
8. To remove the camshaft from the front of the engine, install Tooling (E) on the rear of the
camshaft.
9. Carefully slide the camshaft to the front of the engine for removal. Use two technicians to
remove the camshaft. Keep the camshaft level while the camshaft is being removed from
the cylinder head. The weight of the camshaft is approximately 39 kg (86 lb).
Sun Mar 7 16:02:10 UTC+0800 2021
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Shutdown SIS
Previous Screen
i02963221
Camshaft - Install
SMCS - 1210-012
Installation Procedure
Table 1
Required Tools
A 9U-7257 Cradle 1
B 9U-7256 Guide 1
C 9U-7225 Camshaft Pilot 2
D 9U-7240 Camshaft Hook 2
H 9U-7243 Alignment Sleeve 1
J 9S-3263 Thread Lock Compound 1
K 8T-2998 Lubricant 1
NOTICE
1. Ensure that the camshaft and camshaft bearings are thoroughly clean. Lubricate the
camshaft lobes with a 50/50 mixture of Tooling (K) and clean engine oil. Apply a thin coat
of clean engine oil on the camshaft bearings.
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2. Install Tooling (A) on the cylinder head at Location (Y) .
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3. Install Tooling (B) on front housing (7) . Do not tighten the bolts that hold Tooling (B) to
front housing (7) at this time.
4. Use Tooling (H) to align Tooling (B) with the camshaft bearings. Tighten the bolts that hold
Tooling (B) to front housing (7) . Remove Tooling (H) .
Note: Tooling (H) should move freely from the bore of Tooling (B) .
5. Install Tooling (C) in the end of camshaft (8) .
Note: Rotate the camshaft during installation. This will prevent the camshaft from binding
in the camshaft bearings.
6. Use a suitable lifting device in order to position camshaft (8) into Tooling (B) and the
cylinder head. The weight of the camshaft is approximately 39 kg (86 lb).
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Note: Tooling (C) must be removed before the camshaft can be completely installed in the
cylinder head.
7. Remove the lifting device. Rotate the camshaft during installation. Use care not to allow the
end of the camshaft and Tooling (C) to drop. Use Tooling (D) to assist in aligning camshaft
(8) with the camshaft bearings.
8. Remove Tooling (C) and finish installing camshaft (8) in the bore.
9. Remove Tooling (A) and Tooling (B) .
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10. Install O-ring seals (5) and (6) in seal assembly (3) . Lubricate seal (6) with Tooling (K) .
11. Install seal assembly (3) . Position adapter (4) . Ensure that the dowel in adapter (4) engages
the hole in the camshaft.
12. Position thrust plate (1) . Apply Tooling (J) to bolts (2) . Hold thrust plate (1) in position
and install bolts (2) . Evenly tighten bolts (2) until seal assembly (3) and O-ring seal (5) are
Note: Be careful in order to ensure that O-ring seal (5) stays in the groove in seal assembly
(3) .
End By:
a. Install the rocker arms and the rocker shafts. Refer to Disassembly and Assembly, "Rocker
Arm and Shaft - Install".
b. Install the camshaft gear. Refer to Disassembly and Assembly, "Camshaft Gear - Remove
and Install".
Alternative Installation Procedure
Table 2
Required Tools
E (1)
177-8001 Sleeve 1
F 177-8002 Adapter 1
G 6L-4697 Bolts 3
J 9S-3263 Thread Lock Compound 1
K 8T-2998 Lubricant 1
( 1 )
Part of 177-8003 Engine Tool Group
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NOTICE
1. Ensure that the camshaft and camshaft bearings are thoroughly clean. Lubricate the
camshaft lobes with a 50/50 mixture of Tooling (K) and clean engine oil. Apply a thin coat
of clean engine oil on the camshaft bearings.
2. Install Tooling (F) on the front of camshaft (9) with Tooling (G) .
3. Install Tooling (E) .
4. Use two technicians to install the camshaft. Carefully slide camshaft (9) into the cylinder
head from the rear of the engine. Keep the camshaft level while the camshaft is being
installed in the cylinder head. The weight of the camshaft is approximately 39 kg (86 lb).
5. Remove Tooling (F) .
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6. Install Tooling (F) on the end of the camshaft.
7. Use two technicians to install the camshaft. Carefully slide camshaft (9) into the cylinder
head from the rear of the engine. Keep the camshaft level while the camshaft is being
installed in the cylinder head. The weight of the camshaft is approximately 39 kg (86 lb).
8. Remove Tooling (F) .
9. Position cover (8) on the rear of the cylinder head. Install bolts (7) .
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10. Install O-ring seals (5) and (6) in seal assembly (3) . Lubricate seal (6) with Tooling (K) .
11. Install seal assembly (3) . Position adapter (4) . Ensure that the dowel in adapter (4) engages
the hole in the camshaft.
12. Position thrust plate (1) . Apply Tooling (J) to bolts (2) . Hold thrust plate (1) in position
and install bolts (2) . Evenly tighten bolts (2) until seal assembly (3) and O-ring seal (5) are
Note: Be careful in order to ensure that O-ring seal (5) stays in the groove in seal assembly
(3) .
End By:
a. Install the rocker arms and the rocker shafts. Refer to Disassembly and Assembly, "Rocker
Arm and Shaft - Install".
b. Install the camshaft gear. Refer to Disassembly and Assembly, "Camshaft Gear - Remove
and Install".
Sun Mar 7 16:03:06 UTC+0800 2021
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