Daewoo doosan dx420 lc 5 excavator service repair manual serial number 10001 and up

Original InstructionsCopyright DOOSAN 2014
Serial Number 10001 and Up
Shop Manual
DX420LC-5 Excavator
950106-01020E
April 2014
DOOSAN and the DOOSAN logo are registered
trademarks of DOOSAN Corporation in the United
States and various other countries around the
world.

Table of Contents
Page I
1Table of Contents
1 Safety 1 Track Excavator Maintenance Safety
2 Specifications 1 Specifications
3 General Maintenance 1 General Maintenance Instructions
2 Standard Torques
4 Engine 1 Engine
2 Engine Coolant Heater (Option)
5 Upper Structure 1 Cabin
2 Counterweight
3 Oil Tank
4 Fuel Tank
5 Main Pump
6 Drive Coupling (Main Pump)
7 Main Control Valve
8 Swing Device
9 Fan Pump for Oil Cooler
10 Fan Motor for Oil Cooler
11 Gear Pump (Rotation)
12 Joystick Valve (Work Lever)
13 Travel Control Valve (with Damper)
14 Solenoid Valve
15 EPPR Valve
16 Accumulator

Table of Contents
Page II
6 Lower Structure and Chassis 1 Swing Bearing
2 Center Joint
3 Travel Device
4 Track Assembly
7 Front 1 Boom and Arm
2 Bucket
3 Cylinders
8 Hydraulic System 1 Hydraulic System
2 Hydraulic System Testing and Adjustment
3 Hydraulic System Troubleshooting
9 Electrical System 1 Electrical System
2 Electrical System Troubleshooting
10 Options 1 One Way
2 Two-way
3 Rotating
4 Quick Coupler
11 Schematic 1 Hydraulic Schematic/Electrical Schematic

Track Excavator Maintenance Safety
1-1-1
DX420LC-5
Track Excavator
Maintenance
Safety
Edition 1

1-1-3
DX420LC-5
Table of Contents
Safety Instructions ..........................................1-1-5
Safety Messages ............................................1-1-5
General...........................................................1-1-6
Transportation ..............................................1-1-19
Operation......................................................1-1-21
Maintenance .................................................1-1-38
Environment and Circumstances..................1-1-55

1-1-5
DX420LC-5
SAFETY INSTRUCTIONS
SAFETY MESSAGES
Replace with Safety Messages Section on pages III and IV in
the Doosan Operation & Maintenance Manual.
WARNING
AVOID DEATH OR SERIOUS INJURY
Instructions are necessary before operating or servicing
machine. Read and understand the 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. Untrained
operators and failure to follow instructions can cause death
or serious injury.

DX420LC-5Track Excavator Maintenance Safety
1-1-6
GENERAL
Safe Operation is Operator's
Responsibility
Only trained and authorized personnel should operate and
maintain the machine.
Follow all safety rules, regulations and instructions when
operating or performing maintenance on machine.
• Do not operate machine if you are under the influence of
drugs or alcohol. An operator who is taking prescription
drugs must get medical advice to determine if he or she
can safely operate a machine.
• When working with other personnel on a work site, be sure
that all personnel know nature of work and understand all
hand signals that are to be used.
• Be sure that all guards and shields are installed in their
proper location. Have guards and shields repaired or
replaced immediately if damaged.
• Be sure that you understand the use and maintenance of
all safety features such as safety lever and seat belt. Use
them properly.
• Never remove, modify or disable any safety features.
Always keep them in good operating condition.
• Always check for and know the location of underground
and overhead utility lines before excavating.
• Failure to use and maintain safety features according to
instructions in this manual, Safety Manual and Shop
Manual can result in death or serious injury.
Know Your Machine
Know how to operate your machine. Know the purpose of all
controls, gauges, signals, indicators and monitor displays. Know
the rated load capacity, speed range, braking and steering
characteristics, turning radius and operating clearances. Keep in
mind that rain, snow, ice, loose gravel, soft ground, slopes etc.,
can change operating capabilities of your machine.

1-1-7
DX420LC-5
Proper Work Tools and Attachments
Only use work tools and attachments that are recommended by
DOOSAN for use on DOOSAN machines. When installing and
using optional attachments, read instruction manual for
attachment, and general information related to attachments in this
manual. Because DOOSAN cannot anticipate, identify or test all
attachments that owners may want to install on their machines,
contact DOOSAN for written authorization and approval of
attachments, and their compatibility with optional kits.
Attachments and attachment control systems that are
compatible with the machine are required for safe and reliable
machine operation. Do not exceed maximum operating weight
(machine weight plus attachment) that is listed on ROPS
certification plate.
Make sure that all guards and shields are in place on machine
and on work tool. Depending on type or combination of work
equipment, there is a potential that work equipment could
interfere with the cabin or other parts of machine. Before using
unfamiliar work equipment, check if there is any potential of
interference, and operate with caution.
While you are performing any maintenance, testing, or
adjustments to attachments, stay clear of the following areas:
cutting edges, pinch points, and crushing surfaces.
Never use attachment as a work platform or manlift.
Contact your DOOSAN distributor about auxiliary hydraulic kits
for attachments installation. If you are in doubt about
compatibility of a particular attachment with a machine, consult
your DOOSAN distributor.
Pressurized Fluids
Pressurized air or fluids can cause debris and/or fluids to be
blown out. This could result in death or serious injury.
Immediately after operations are stopped, coolant, engine oil,
and hydraulic oil are at their highest temperatures and the
radiator and hydraulic tank are still under pressure. Always wait
for temperature to cool down. Follow specified procedures when
attempting to remove caps, drain oil or coolant, or replacing
filters. Always wait for temperature to cool down, and follow
specified procedures when performing these operations. Failure
to do so can result in death or serious injury.
When pressurized air and/or pressurized water is used for
cleaning, wear protective clothing, protective shoes, and eye
protection. Eye protection includes goggles or a protective face
shield.
Pressure can be trapped in a hydraulic system and must be
relieved before maintenance is started.
Releasing trapped pressure can cause sudden machine
movement or attachment movement. Use caution if you
disconnect hydraulic lines or fittings.
FG018457
Figure 1

DX420LC-5Track Excavator Maintenance Safety
1-1-8
High-pressure oil that is released can cause a hose to whip or oil
to spray. Fluid penetration can result in death or serious injury. If
fluid enters skin or eyes, get immediate medical attention from a
physician familiar with this injury.
Obey all local laws and regulations for disposal of liquids.
To prevent hot coolant from spraying out, stop engine and wait
for coolant to cool. Using gloves, slowly loosen cap to relieve
pressure.
Flying or Falling Objects
On work sites where there is a potential hazard that flying or
falling objects can hit operator's cabin, select and use a guard to
match operating conditions for additional operator protection.
Working in mines, tunnels, deep pits, and loose or wet surfaces,
could produce hazard of falling rocks or flying objects. Additional
protection for operator's cabin could be required such as an
Operator Protection Guard (OPG) or window guards. Contact
your DOOSAN distributor for information on available protective
guards.
To prevent personnel from being struck by flying objects, keep
personnel out of work area.
HAOA110L
Figure 2
HAOA100L
Figure 3

DX420LC-5Engine
4-1-1
Engine
Edition 1

Engine
4-1-57
DX420LC-5
Removal Cylinder Head
1. Remove water-cooled EGR cooler as instructed in the
work description for "Removing the EGR Cooler" on
page 4-1-267.
Remove brackets for the water-cooled EGR cooler.
2. Remove bolts for the exhaust manifold on the relevant
cylinder and slacken the bolts on the adjacent cylinders so
the relevant part of the exhaust manifold comes loose.
3. Remove cooling system bleeder hose, separate the quick
release coupling at the front lifting eye.
4. Remove cable duct from the intake.
5. Remove cable ties for the cable harness from the engine
control unit.
6. Depressurize the fuel system and detach the fuel pipe (1,
Figure 29) running between the accumulator and fuel
manifold.
7. Detach the fuel manifold and remove bolts on the relevant
cylinder.
8. Detach the intake manifold and remove bolts on the
relevant cylinder. To remove fuel and intake manifold, see
"Fuel Manifold" and "Intake Manifold".
9. Remove injectors as instructed in the work description for
"Removing Injector" on page 4-1-311.
Also remove high-pressure pipes and connection on the
cylinder head at the back viewed from the coolant pump.
IMPORTANT
The fuel system components are extremely sensitive
to dirt. Clean thoroughly before dismantling and plug
all connections with lint-free rags and tape.
EX1401040
1
Figure 29
IMPORTANT
All parts in the fuel injection system and valve
mechanism must be marked.
Everything must be reinstalled in the same position.

DX420LC-5Engine
4-1-58
10. Remove upper rocker cover and then the rocker arm
housing, valve bridges and pushrods.
11. Pull the cable harness out of the lower rocker cover and
remove it.
NOTE: Take care when pulling the cable harness out of
the rocker cover: the cable terminals can be
damaged which can cause the nut securing the
cable harness to the injector to come loose.
12. Work on the adjacent cylinders. Remove upper rocker
cover, release the cable harness and the lower rocker
cover so it can be moved.
13. Remove relevant cylinder head. Be careful with the
adjacent rocker covers.
NOTE: Mark the cylinder heads if more than one is
being removed at the same time.
NOTE: If all cylinder heads are removed at the same
time, the turbocharger must be removed or
supported against the frame.
Installing Cylinder Head
1. Check the liner height.
2. Clean the cylinder head and cylinder block. Lubricate the
threads and below the heads of the cylinder head bolts.
3. Install a new cylinder head gasket.
4. Install the cylinder head.
5. Tighten the cylinder head as shown in the illustration and
according to specification.
Cylinder head bolts can only be reused three times. Make
a mark with a center punch on the head of the bolt. If any of
the bolts already has three marks, it must be replaced.
FG020251
Figure 30
IMPORTANT
If work is done on the 6th cylinder of an engine with an
EGR system, the EGR valve control cylinder must be
detached at the damper and removed.
FG020252
Figure 31
1
2
3
4
5
6
FG020253
Figure 32

Engine
4-1-59
DX420LC-5
6. Tighten the intake manifold. Use a new gasket. Tighten the
bolts in the order 1 - 24 as illustrated. Tighten the bolts in
the same order again.
7. Tighten the intake manifold and the exhaust manifold. Use
new gaskets.
8. Install the cable bracket bolt in the lower rocker cover and
install the following parts:
• Lower rocker cover.
• Pushrods.
• Valve bridge.
• Rocker arm housing.
9. Install the injector, high-pressure pipe connection and
high-pressure pipe as instructed in the work description.
10. Reset adjacent cylinders.
11. Adjust the valve clearance.
12. Install the upper rocker covers.
13. Install the cooling system vent
Install the brackets for the water-cooled EGR cooler.
Install the water-cooled EGR cooler as described in the
work description for "Installing the EGR Cooler" on page 4-
1-268.
FG020254
1 2 3 4
Figure 33
Figure 34
IMPORTANT
Lubricate the valve bridge and rocker arm housing
with engine oil.

DX420LC-5Engine
4-1-60
Removing and Installing Valves
1. Removing Valves
A. Remove split collets, valve spring collars, springs and
valves. Press down the spring using tool 99 322 in a
press so the collets can be removed.
B. Place the valves in a stand so they can be reinstalled
in the same position in the cylinder head.
2. Installing Valves
NOTE: There are different versions of the combination
valve – valve spring collar – split collet. Parts
from the different versions must not be mixed
on the same valve.
A. Lubricate all parts well with engine oil before
assembly.
B. Insert the valve in the guide.
C. Install the valve springs and the valve spring collar.
D. Press together the springs in a press with tool 99 322
and install the collets. Ensure that collets are installed
in their correct positions.
Replacing a Valve Stem Seal
1. Remove valve according to the work description for
"Removing Valves" on page 4-1-75.
2. Remove valve stem seal with a pair of pliers.
3. Install the valve.
WARNING
Wear protective goggles for eye protection.
99 322
FG020258
Figure 35
FG020259
99 322
Figure 36
FG020261
Figure 37

Engine
4-1-61
DX420LC-5
4. Carefully tap a new valve stem seal into place using tool 99
323 and a hammer.
Replacing the Valve Seats
1. Remove valve seat inserts with an expanding sleeve from
the kit with puller 587 270 (1, Figure 39).
NOTE: Insert, for example, an aluminum sheet
between the cylinder head and counterhold to
protect against damage.
2. Press in new valve seat inserts. Use drift 99 384 (2, Figure
39) and shank 99 385. Cool the drift and valve seat insert
to about -80°C with dry ice or liquid air. Pressing must be
done rapidly.
Oversize valve seat inserts can be installed if the valve
seat insert position has been damaged.
The position is then machined using tool 587 277.
99 323
FG020262
Figure 38
2
1
FG020266
Figure 39
WARNING
Wear protective goggles for eye protection from flying
metal parts.
99 385
99 384
FG020267
Figure40
WARNING
Prevent frost injuries. Be careful when handling very
cold parts and refrigerant.

DX420LC-5Engine
4-1-62
Replacing the Valve Guides
1. Press out the valve guides using drift 99 383.
2. Press in the new valve guides using drift 99 382. Press the
guide down as far as the drift allows, i.e. until it contacts
the spring seat in the cylinder head.
Replacing the Injector Sleeves
The cylinder head must be removed when replacing the unit
injector sleeve. The valves do not need removing. The
illustrations show the cylinder head with valves removed to
demonstrate clearly the work described.
NOTE: Guide and pilot tap on extension piece 99 397.
99 383
FG020268
Figure 41
99 382
FG020269
Figure 42
FG020272
Figure 43

Engine
4-1-63
DX420LC-5
1. Thread the lower part of the sleeve using the pilot tap and
guide from tool kit 99 574.
2. Knock out the pilot tap and sleeve from underneath. Use a
100 mm long metal rod of diameter 9 mm.
3. Degrease and check the contact surfaces of the sleeve
and cylinder head. Smooth off any burrs and irregularities
that may score the sleeve.
4. Degrease the new injector sleeve and apply a thin film of
sealant 561 200 on the sleeve and cylinder head contact
surfaces.
5. Press in the sleeve using the drift and guide from tool kit 99
574.
FG020273
Figure 44

DX420LC-5Engine
4-1-64
Replacing the Valve Bridge Guide Pins
The cylinder head must be removed when replacing the guide
pins.
1. Remove Outlet valves and Intake valves.
2. Install shrink sleeve number 10 from tool kit 587 470.
3. Use pin extractor 587 470 to remove guide pins.
12
FG020276
Figure 45
Reference
Number
Description
1 Outlet Valves
2 Intake Valves
FG020277
Figure 46
FG020278
587 470
Figure 47
FG020279
Figure 48

Engine
4-1-65
DX420LC-5
4. Press in the new guide pins using drift 99 015. Maximum
press force 15 kN.
NOTE: Check before pressing in that tool is not
deformed.
Check after pressing in that valve bridge slides
easily on the guide pin.
5. Install all the parts in the cylinder head.
Machining the Valve Seat Position
1. Check that contact surface on the cylinder head is level
and clean. Also check that magnetic stand on the valve
seat cutter is clean. Clean the valve guides.
2. Zero the micrometer.
3. Assemble the micrometer with a suitable spindle on the
valve seat cutter and adjust the cutter. It is very important
that tip of the cutter is in the center of the micrometer
spindle.
FG020280
99 015
Figure 49
FG020282
Figure 50
FG020283
Figure 51

DX420LC-5Engine
4-1-66
4. Select the largest control spindle that moves easily in the
valve guide. Install the valve seat cutter and turn the feed
screw to its upper position.
5. Turn off the magnet (position 2). Insert the guide spindle
into the valve guide. Adjust the pivot plate so the distance
between the cutter and the valve seat is approximately
1 mm.
Center the valve seat cutter precisely.
6. Turn on the magnet (position 1).
7. Apply the quick-action lock. Make sure the crank can be
turned easily. If not, redo the centering.
8. Machine the valve seat by cranking clockwise while turning
the screw clockwise. Lubricate with cutting oil while
machining.
9. When the surface of the valve seat has been machined,
reduce the cutting pressure by turning 2-3 revolutions
without any feed. Continue turning clockwise while turning
the screw counterclockwise until cutter is free. Disconnect
the solenoid by briefly pressing switch position 2.
10. The valve seat cutter is now ready for the next valve seat.
FG020284
Figure52
FG020285
Figure 53
FG020286
Figure 54
IMPORTANT
The cutter must never be cranked counterclockwise.

Engine
4-1-67
DX420LC-5
Removing the Valve Seat Insert
1. Remove cylinder head. According to the word description
for "Removal Cylinder Head" on page 4-1-57.
2. Remove intake and exhaust valves. According to the word
description for "Removing and Installing Valves" on
page 4-1-60.
NOTE: Insert, for example, an aluminium sheet
between the cylinder head and counterhold to
protect against damage.
Remove valve seat inserts with an expanding sleeve from
the kit with puller 587 270.
Machining the Reducer Chamfer
2. Adjust the cutting blade for a 51° reducer chamfer on the
valve seat cutter and set the distance to approximately
21 mm as illustrated.
3. Select the largest control spindle that moves easily in the
valve guide. Install the valve seat cutter and turn the feed
screw to its upper position.
4. Lubricate the control spindle and insert it in the valve
guide.
Figure 55
IMPORTANT
Wear protective goggles. There is a risk that loose
slivers of metal can cause personal injury when
pulling out the valve seats.
Figure 56
Figure 57

DX420LC-5Engine
4-1-68
5. Adjust the pivot plate so distance between the cutter and
the reducer chamfer is approximately 1 mm. Center the
valve seat cutter precisely.
8. Mill the reducer chamfer by cranking clockwise while
turning the feed screw clockwise. Make sure you do not
make the outer diameter of the reducer chamfer larger, as
shown in the illustration.
9. When the surface of the reducer chamfer has been machined,
reduce the cutting pressure by turning 2 ~ 3 revolutions without
any feed. Continue turning clockwise while turning the screw
counterclockwise until cutter is free. Disconnect the solenoid by
briefly pressing switch position 2.
10. Continue with the next reducer chamfer as described in the
steps above.
Figure 58
Figure 59
Figure 60
IMPORTANT

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Engine
4-1-69
DX420LC-5
Installing a New Valve Seat Insert
1. Clean the cylinder head.
2. Tap/press in new valve seat inserts. Use drift 99 384 and
shank 99 695. Cool the drift and valve seat insert to about -
80°C with dry ice or liquid air. The tapping/pressing in must
be done very rapidly.
Oversize valve seat inserts can be installed if the valve
seat insert position has been damaged. The position must
then be machined with tool 587 277.
Machining the Valve Seat Insert Sealing Surface
2. Adjust the cutting blade for a 30° valve seat position on the
valve seat cutter and set the distance to approximately 17
mm as illustrated.
3. Lubricate the control spindle and insert it in the valve
guide.
Figure 61
WARNING
Be careful when handling the cold parts and
refrigerant mentioned above. Risk of frost injuries.
Figure 62

DX420LC-5Engine
4-1-70
4. Adjust the pivot plate so distance between the cutter and
the valve seat insert is approximately 1 mm. Center the
valve seat cutter precisely.
7. Perform minimal machining of the valve seat insert sealing
surface by cranking clockwise while turning the feed screw
clockwise. Continue until it can be seen that entire sealing
surface is machined.
Figure 63
Figure 64
Figure 65
IMPORTANT

Engine
4-1-71
DX420LC-5
8. When the sealing surface of the valve seat insert has been
machined, reduce the cutting pressure by turning 2 ~ 3
revolutions without any feed. Continue turning clockwise
while turning the screw counterclockwise until cutter is
free.
Disconnect the solenoid by briefly pressing switch position 2.
9. Continue with the next valve seat insert as described in the
steps above.
Height Check of Valve Seat Insert
1. Make sure that cylinder head is clean.
NOTE: Use the same exhaust valve for the
measurement below to avoid measurement
errors.
2. Install the exhaust valve in the first valve guide. Measure
the height of the exhaust valve.
3. Install the same exhaust valve in the second valve guide.
Measure the height of the exhaust valve.
4. The height tolerance between exhaust valves is ±0.05 mm.
If the difference is greater, machine the valve seat insert
which is highest until height tolerance is obtained.
Also check that distance between the valve disk and the
bottom of the cylinder head is not less than 0.71 mm as
shown in the illustration.
Figure 66
Figure 67
Figure 68

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