PDF Service Manual Bobcat 641 642 643 Skid Steer Loader - 4 MB
This service manual provides comprehensive maintenance and repair information for the classic Bobcat 641, 642, and 643 skid steer loaders.
It's the same manual used by factory-trained technicians, offering detailed procedures for everything from routine service to major overhauls.
Keep your vintage Bobcat running strong with this essential guide.
The manual is a must-have for any owner or mechanic working on these durable machines.
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6 6
4 4
1 3
2
INCLUDES
H SERIES
Service
6 Manual
4
3
6566135 (10–86) Printed in U.S.A. © Melroe Company 1996
--- Page 3 ---
1–PREVENTIVE MAINTENANCE
1–1 INTRODUCTION Loader Serial
Number
The Preventive Maintenance Section of this Service Manual gives general
maintenance procedures for the Bobcat loader. The other sections of the Service
Manual will give the detailed description needed for disassembly and assembly
and when replacement parts are needed.
1–1.1 Serial Number Identification
It is important to make correct reference to the Serial Number of the Bobcat loader
and/or engine when making repairs or ordering parts. It is possible that the present B–02674R
loaders do not use all the same parts as the earlier loaders. It is possible that Fig. 1–1 Loader Serial Number
different procedures are used for service repair.
1–1.2 Loader Serial Number
Engine Serial
The Bobcat loader serial number plate Number
location is on the inside of the left upright,
above the grill (Fig. 1–1).
Explanation of the Serial Number: B–02249
Fig. 1–2 (641) Engine Serial Number
XXXX M XXXX
Production Sequence (Series)
Plant Location
Model, Engine Version
1–1.3 Engine Serial Number
641 Deutz: (Fig. 1–2) The engine
serial number location is on the right Engine Serial
side of the cylinder block. Use all the Number
numbers when ordering parts for this
engine.
642 Ford: (Fig. 1–3) The engine serial Engine Serial
number location is on the right side of Number
the valve cover. Use all the numbers
when ordering parts for this engine.
643 Kubota: (Fig. 1–4) The engine
serial number location is on the left
side above the speed control arm. Use
all the numbers when ordering parts
for this engine.
B–02796 B–04940
Fig. 1–3 (642) Engine Serial Number Fig. 1–4 (643) Engine Serial Number
641, 642, 643 Loader
–1–1– Service Manual
--- Page 4 ---
1–5.1 Removing Coolant From The Cooling System
To remove coolant (642):
1
2
Do not remove radiator cap when the engine is
hot. You can be seriously burned.
W–2070–1285
A–02466
Fig. 1–27 Sender Switch (642)
1. Put a funnel under the temperature sender switch (Fig. 1–27, Item 1) to keep
coolant from getting into the engine compartment.
2. Remove the grill (Fig. 1–28, Item 1).
3. Remove the radiator cap (Fig. 1–28, Item 2). The grill must be removed to
do this.
4. Remove the wire (Fig. 1–27, Item
2) connected to the sender switch.
Remove the sender switch (Fig.
1–27, Item 1).
To fill the cooling system (642): 2
1. Install the sender switch (Fig.
1–27, Item 1).
2. Connect the wire (Fig. 1–27, Item
2) to the sender switch. 1
3. Premix 50% water and 50%
anti–freeze in a separate container
(See Paragraph 8B–1.8, Page
8B–2 for capacity).
4. Fill the radiator with the mixed
coolant and install the radiator cap.
B–03855
5. Install the grill (Fig. 1–28, Item 1). Fig. 1–28 Grill And Radiator Cap
6. Fill the coolant recovery tank 1/3
full.
NOTE: Protect the cooling system from freezing temperatures and
overheating by adding premixed 50/50 ethylene glycol and water to
the system.
To remove coolant from the cooling system (643):
Valve
Do not remove radiator cap when the engine is
hot. You can be seriously burned.
W–2070–1285
The valve to remove the coolant is on the left side of the engine block (Fig. 1–29). B–03599R
Fig. 1–29 Valve For Removing Coolant
Revised Dec. 83 (643)
641, 642, 643 Loader
–1–11– Service Manual
--- Page 5 ---
SPARK ARRESTOR MUFFLER
The spark arrestor muffler must be
cleaned every 100 hours. Wear safety
goggles.
WARNING
1
Stop engine and allow the muffler
to cool before cleaning the spark
chamber. Wear safety goggles.
Failure to obey can cause serious
injury. W–2011–1285
B–04100
Fig. 1–59 Spark Arrestor Muffler (641)
1. Stop the engine.
1
2. Open the rear door.
3. Remove the plug at the bottom of the muffler (641, Fig. 1–59, Item 1) (642,
Fig. 1–60, Item 1) (643, Fig. 1–61, Item 1).
DO NOT run the engine in an area
WARNING that has materials that can cause
combustion. Wear safety goggles. B–04259
W–2309–0398 Fig. 1–60 Spark Arrestor Muffler (642)
4. Hold a block of wood over the outlet of the muffler.
5. Start the engine and run it for about 10 seconds.
1
6. Stop the engine and install the plug.
7. Close the rear door.
B–04038
Fig. 1–61 Spark Arrestor Muffler (643)
641, 642, 643 Loader
–1–21– Service Manual
--- Page 8 ---
2–3 HYDRAULIC CONTROL VALVE
(Victor)
When repairing hydrostatic and
hydraulic systems, clean the
work area before disassembly
and keep all parts clean. Always
use caps and plugs on hoses,
tubelines and ports to keep dirt
out. Dirt can quickly damage the
system. I–2003–0888
B–04058
Wear in the control valve or spools will Fig. 2–3 Checking The Relief Valve
cause the hydraulic cylinders to move
when the controls are in neutral position.
Wear can also cause loss of hydraulic
power.
If the lift arm or tilt cylinder still move or extend after they have been checked and
no damage has been found, check the control valve for the following:
1. Spool not centering in the valve section when the pedal is released. The
spring can be broken or check the pedal linkage and adjust it so it will keep
the spool in the neutral position.
2. Check for leaks in the valve because of wear or damaged valve body.
3. Replace valve as necessary.
2–3.1 Relief Valve
Checking The Relief Valve
The tools listed will be needed to do the following procedure:
MEL10003 Tester
MEL10006 Flow Meter Test Kit
NOTE: Oil must be warm to do this procedure.
1. Stop the engine.
Loader must be restrained for some service
and repair. When balance of loader is changed
by removal of lift arms or engine, or when it is
necessary to rotate axles, jackstands should be
put under both front axles and both rear
corners of frame. Blocks by wheels can be
climbed and do not stop loader.
W–2310–0398
2. Activate the auxiliary hydraulic control (right steering lever) to release the
hydraulic pressure.
3. Connect the male–end quick coupler to the inlet of the tester and the
female–end quick coupler to the outlet (Fig. 2–3).
Revised Dec. 83 641, 642, 643 Loader
–2–3– Service Manual
--- Page 9 ---
13. Remove the spool from the vise.
Put oil on the spool. Carefully install
641–642–643
ServiceManual#6566135–HydraulicSystemSectionPages7a–7f
the spool into the auxiliary section 2
of the control valve. 4 6
3 5 7
1
14. Install the detent end cap.
15. Install the bolts. Tighten the bolts to
90–100 in.–lbs. (10–11 Nm) torque.
16. Install the washer and snap ring on E–01446
the detent sleeve (Fig. 2–45a).
Fig. 2–44a Tilt Centering Spring Assembly
17. Put oil on the O–ring (Fig. 2–44a, Item 1). Install the O–ring on the tilt spool.
18. Put oil on the tilt spool. Carefully install it into the tilt section of the control
valve.
19. Install the back–up washer, end cap, centering spring, end cap and adaptor
(Fig. 2–44a, Items 2 thru 6).
20. Put LOCTITE on the bolt (Fig. 2–44a, Item 7). Install and tighten the bolt to
90–100 in.–lbs. (10–11 Nm) torque.
21. Install the end cap.
22. Install the end cap bolts. Tighten the bolts to 90–100 in.–lbs. (10–11 Nm)
torque.
23. Repeat steps 1 thru 16 to install the detent assembly and the lift spool in the
control valve.
24. Install the O–ring, filter, boot, boot retainer on each of the three spools (Fig.
2–46a).
25. Install the bolts for the boot retainers. Tighten the bolts to 90–100 in.–lbs.
(10–11 Nm) torque on each of the three spools. Check all three spools for
correct function and detent.
26. Install the main relief valve. Tighten to 50–60 ft.–lbs. (68–81 Nm) torque.
27. Install the plug, with new O–rings and back–up washers, into the tilt section
port (Fig. 2–24a, Item F2).
28. Tighten the plug to 50–60 ft.–lbs. (68–81 Nm) torque. B–06447
Fig. 2–45a Detent Sleeve Snap Ring
29. Install the anti–cavitation valve, with new O–rings and back–up washers,
into the tilt section port (Fig. 2–24a, Item E2).
30. Tighten the anti–cavitation valve to 50–60 ft.–lbs. (58–81 Nm) torque.
31. Install the load check valves into the stop section of the control valve (Fig.
2–24a, Items C1, C2 and C3). Use new O–rings and back–up washers.
32. Tighten the load check valves to 50–60 ft.–lbs. (68–81 Nm) torque.
B–05804
Fig. 2–46a Rubber Boot & Retainer
Added May 83 641, 642, 643 Loader
–2–7f– Service Manual
--- Page 10 ---
13. Remove the piston from the tool
and install on the shaft (Fig.
2–69).
14. Install the nut and tighten to
195–205 ft.–lbs. (264–278 Nm)
torque (Fig. 2–70).
15. Put oil on the seals, O–rings
and end cap threads (Fig. B–03692 B–03670
2–71).
Fig. 2–69 Installing The Piston Fig. 2–70 Tightening The Nut
16. Install the assembly in the
cylinder housing (Fig. 2–72).
17. Tighten the end cap with a
spanner wrench (Fig. 2–73).
B–03691 B–03665
Fig. 2–71 Putting Oil On The Seals Fig. 2–72 Installing Assembly
2–5.5 Installation Of The Lift
Cylinder(s)
1. Install the lift cylinder in the
loader.
2. Connect the hydraulic hoses
and tighten (Fig. 2–77).
B–05025
Fig. 2–73 Tightening End Cap
3. Install the pin in the base end of
the lift cylinder (Fig. 2–74).
4. Install the pin in the rod end of
the cylinder.
5. Install the bolt and locknut in the
rod end pin (Fig. 2–75).
B–04397 B–04981
Fig. 2–74 Installing Pin Fig. 2–75 Installing Bolt And Locknut
9
Revised Dec. 83 641, 642, 643 Loader
–2–17– Service Manual
--- Page 11 ---
3 HYDRAULIC SYSTEM
3–1 Troubleshooting
The following troubleshooting chart is provided as an assistance in locating and correcting problems which are most
common. Many of the recommended procedures must be done by authorized Bobcat Service Personnel only.
PROBLEM CAUSE
No drive on one side, in one direction. 1, 2, 3, 4, 5
No drive on one side in both directions. 2, 3, 5, 6, 7, 8
The loader does not move in a straight line. 2, 3, 4, 6, 8, 9, 10
The hydrostatic system is overheating. 4, 11, 12, 13, 14, 15
The warning light comes ON (Low charge pressure). 15, 16, 17, 18
KEY TO CORRECT THE CAUSE
1. The hydrostatic system has a fluid leak.
2. The steering linkage needs adjustment.
3. The high pressure replenishing valve(s) are damaged.
4. The shuttle valve in the hydrostatic motor is not working correctly.
5. The balance plate seals in the hydrostatic motor are damaged.
6. The hydrostatic pumps have damage.
7. The final drive chain is broken.
8. The hydrostatic motor has damage.
9. The tires do not have the correct tire pressure.
10. The tires are not the same size.
11. The hydrostatic fluid is not at the correct level.
12. The oil cooler has a restriction.
13. The temperature sending switch is not operating correctly.
14. The control valve is not operating correctly.
15. The loader is not being operated at the correct RPM.
16. The sender is defective.
17. Pump is defective or worn hydrostatics.
18. 40 micron filter is plugged.
641, 642, 643 Loader
–3–1– Service Manual
--- Page 12 ---
3–5.4 Removing The Port Block
1. Stop the engine. Drain the hydraulic/hydrostatic reservoir.
2. Raise the operator cab (See Paragraph 5–1, Page 5–1).
B–04911
Fig. 3–32 Removing Hoses
When repairing hydrostatic and hydraulic
systems, clean the work area before
disassembly and keep all parts clean. Always
use caps and plugs on hoses, tubelines and
ports to keep dirt out. Dirt can quickly damage
the system.
I–2003–0888
3. Remove the hydraulic hoses and tubelines from the port block (Fig. 3–32).
4. Remove the small bolt from the port block. Remove the large bolt at the top
of the port block (Fig. 3–33). Use tool MEL1193.
5. Remove the port block from the hydraulic pump.
3–5.5 Installing The Port Block
1. Install new O–rings on the large bolt (Fig. 3–32a).
E–01467
2. Install the port block on the hydraulic pump and tighten the large bolt (Fig.
3–33) so there will be no leakage at 200 PSI (1379 kPa). Fig. 3–32a Large Bolt And O–Rings
3. Install the small bolt in the port block and tighten 25–28 ft.–lbs. (34–38 Nm)
torque.
4. Install the hoses and the tubelines to the correct port in the port block.
5. Fill the hydraulic/hydrostatic reservoir with the correct oil.
6. Lower the operator cab (See Paragraph 5–1, Page 5–1).
7. Start the engine and run the engine for several minutes.
8. Stop the engine and check the reservoir oil level. Add oil as needed.
B–04927
Fig. 3–33 Removing Bolt
Revised Aug. 84 641, 642, 643 Loader
–3–11– Service Manual
--- Page 13 ---
9. Turn the mounting flange while installing it over the shaft. Be careful not to
641–642–643
damage the seals.
ServiceManual#6566135–HydrostaticSystemSectionPages13–19
2 4
7 6
10. Put oil on the threads of the eight bolts (Fig. 3–64, Item 5). Install the bolts
in the mounting flange and tighten them with your hand only. 5 8
3 1 B–03042R
Fig. 3–68 Tightening Sequence
11. Put the motor in a vise and tighten the bolts evenly to 250 in.–lbs. (28 Nm)
torque. Use the correct tightening sequence (Fig. 3–68).
12. Install the key in the keyway of the shaft.
B–05119
Fig. 3–69 Installing Drive Shaft
13. Put the motor in a vise with the output shaft down (Clamp the sides of the
mounting flange only).
14. Put a small amount of oil on the output shaft.
15. Put petroleum jelly on the 3.500 inches (88,9 mm) diameter O–ring and
install it in the outer groove in the bearing housing.
16. Install the main drive in the output shaft (Fig. 3–69).
17. Put petroleum jelly on the two 0.250 inch (6,35 mm) diameter O–rings. Install
the O–rings, one on each side of the geroler ring.
Revised March 84 641, 642, 643 Loader
–3–19– Service Manual
--- Page 14 ---
15. Remove the pintle cover and
the shims (Fig. 3–108 &
3–109).
Avoid damage to the shims B–04960 B–04966
under the pintle covers. If Fig. 3–108 Removing Pintle Cover Bolts Fig. 3–109 Removing Cover And Shims
shims are damaged, install
new shims. Use the procedure
given in the manual to install
shims.
I–2011–0284
16. Remove the O–rings (Fig.
3–110 & 3–111).
B–04993 B–05049
Fig. 3–110 Removing O–Rings Fig. 3–111 Removing O–Rings
17. Remove the bearing spacers
from the pump housing (Fig.
3–112 & 3–113).
B–05051 B–05052
Fig. 3–112 Removing Bearing Spacers Fig. 3–113 Removing Bearing Spacers
18. Move the yoke from side to side
to loosen the bearing races.
Remove the races and the
bearings (Fig. 3–114).
19. Turn the yoke at an angle and
remove the yoke and the shaft
together (Fig. 3–115). B–05050
B–04979
Fig. 3–114 Removing Races And
Bearings Fig. 3–115 Removing Yoke And Shaft
641, 642, 643 Loader
–3–27– Service Manual
--- Page 15 ---
IMPORTANT
Use the correct wafer plate (Fig.
3–149). Plates with two or four
feathering grooves (Fig. 3–149,
Item 1) are interchangeable, but
front and rear plates are not
interchangeable.
I–2166–0398
Cylinder
3. Put the splined coupler on the 1 1 Block
drive shaft (Fig. 3–150). Cylinder Rotation
Block (Rear Pump)
Rotation Front Rear
(Front Pump) Pump Pump
4. Make sure the gasket and the B–04977
alignment pins are in the correct Fig. 3–149 Correct Wafer Plate
location and install the housing on
the manifold block.
5. Install the six screws and tighten 23–26 ft.–lbs. (31–35 Nm) torque.
6. Turn the vane pump shaft in the intermediate shaft until it is against the
shoulder. Then turn the vane pump shaft out to align the splines.
7. Put the splined coupling over the splines on the intermediate shaft and the
vane pump shaft.
8. Install the snap ring in the groove on the vane pump shaft.
9. Install the wafer plate (For #2 housing). The wafer plate must be flat against
the manifold block.
Use the correct wafer plate (Fig. B–04994
3–149). Plates with two or four
IMPORTANT feathering grooves (Fig. 3–149, Item
1) are interchangeable.
Fig. 3–150 Installing Coupler
I–2166–0398
10. Make sure the gasket and the alignment pins are in position and install the
housing on the manifold block. Turn the vane pump shaft so that the splines
are in alignment.
11. Install the six screws and tighten 23–26 ft.–lbs. (31–35 Nm) torque.
12. Install the large O–ring on the end of the #2 housing and install the vane
pump.
13. Install the two screws to hold the vane pump and tighten 54–66 ft.–lbs.
(73–89 Nm) torque.
9
Revised Dec. 83 641, 642, 643 Loader
–3–35– Service Manual
--- Page 16 ---
11. Use a puller to remove the outer
bearing cone (Fig. 4–21).
12. Clean and check all the parts for
wear and damage.
4–3.2 Assembly Of The Axles
1
Bearing
1. Lubricate the new axle seal C–02528
(Fig. 4–22, Item 1) and install Fig. 4–22 Axle Wear Sleeve
the seal over the axle flange.
NOTE: The spring loaded side of
the seat must be up. B–02813
Fig. 4–21 Removing The Outer Bearing
2. Pack bearings with grease.
3. Install the bearing cone on the
axle and drive the bearing over
the first raised surface of the
axle using a pipe (Figure 4–23).
DO NOT damage the bearing.
4. Drive the bearing onto the axle
over the second raised surface
using the pipe (Fig. 4–24).
5. Install the outer axle bearing
cup using an arbor of the
correct size (Fig. 4–25). The
inner bearing cup can be pulled
into position using a long bolt
and a washer.
4–3.3 Installing The Axles B–03981
The tool listed will be needed to do Fig. 4–23 Installing Bearing
the following procedure:
MEL1051 Seal Installation Tool
B–03984
1. Put the sprocket into the Fig. 4–24 Installing Bearing
chaincase with the chain in
position.
NOTE: The wide part of the
sprocket hub goes toward
the inside for the front
axles and toward the
outside on the rear axles.
2. Install the axle assembly into
the axle housing.
3. Install the inner halves of the
installation tool MEL1051, used
to install the axle (Fig. 4–16).
B–03982 B–02770
Fig. 4–25 Installing Bearing Cup Fig. 4–26 Axle Installation Tool
Revised Dec. 83 641, 642, 643 Loader
–4–7– Service Manual
--- Page 17 ---
5–3.4 Installing The Bob–Tach
1. Position the Bob–Tach between
the lift arms.
2. Using a punch push the pivot
pin into the lift arms (Fig. 5–33)
using the grease fitting hole.
B–04889
Fig. 5–33 Putting Pin Into Position
3. Install the bolt into the pivot pin
and tighten to 125–140 ft.–lbs.
(170–190 Nm) torque.
4. Install the grease fitting and
tighten.
5. Put the floor jack under the
Bob–Tach.
1
6. Install new seals at the rod end
of the tilt cylinder shaft (Fig.
5–34).
B–04405 B–04406
Fig. 5–34 Installing Seals Fig. 5–35 Installing Rod End
7. Lift the Bob–Tach with the floor
jack.
8. Put a piece of shim stock (Fig.
5–35, Item 1) on each side of
the seals at the rod end of the
cylinder. Install the rod end of
the tilt cylinder in the Bob–Tach
frame.
9. Install the rod end pin (Fig.
5–36). B–04873
Fig. 5–36 Installing Pin
Revised Dec. 83 641, 642, 643 Loader
–5–7– Service Manual
--- Page 18 ---
ELECTRICAL SYSTEM
Paragraph Page
Number Number
ALTERNATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–6 6–5
BATTERIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–3 6–3
ELECTRICAL SYSTEM INFORMATION . . . . . . . . . . . . . . . . 6–2 6–2
STARTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–7 6–9
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–1 6–1
WIRE HARNESS FOR THE ENGINE . . . . . . . . . . . . . . . . . . . 6–5 6–5
WIRE HARNESS FOR THE
OPERATOR GUARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–4 6–3
ELECTRICAL
SYSTEM
Instructions are necessary before operating or
servicing machine. Read Operation &
Maintenance Manual, and signs (decals) on
machine. Follow warnings and instructions in
the manuals when making repairs, adjustments
or servicing. Check for correct function after
adjustments. repairs or service. Failure to
follow instructions can cause injury or death.
W–2144–0189
641, 642, 643 Loader
–6––1– Service Manual
--- Page 22 ---
9. Connect the wire harness connectors (Fig. 6–2).
10. Connect the negative cable to the battery.
11. Close the rear door.