Sauer Danfoss 20 Series User manual

Series 20
Axial Piston Pumps
Service Manual and
Repair Instructions
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:021

2DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Introduction, Description
INTRODUCTION
DESCRIPTION
The purpose of this manual is to provide you with the information necessary for the
normal maintenance and servicing of the Sauer-Danfoss hydrostatic series 20 units.
This includes a description of the units and their components as well as troubleshooting,
pressure setting and repair procedures.
Minor repairs may be performed without affecting the warranty. Major repairs performed
during the warranty time could eventually affect the warranty.
To facilitate easy servicing, the unit has been designed with this in mind.
Many of the individual parts and assemblies are interchangeable throughout the entire
series 20 family. This includes such items as the servo valve, the charge pumps and the
manifold components.
In addition, many repairs and adjustments can be performed without having to remove
the unit from the vehicle, provided that the unit is easily accessible and a thorough
cleaning of the unit is possible before beginning with repairs.
Dirt or other forms of contamination are in most cases the reason for the breakdown
of a hydraulic unit. Please pay attention to cleanliness, not only when making repairs,
but also when putting the unit into operation, changing the oil, changing lters or any
other procedures.
The following manual will provide you with comprehensive instructions for preventative
maintenance and recognition of causes of failure of the axial-piston units.
Sauer-Danfoss axial piston variable displacement pumps are of swash plate design with
variable ow capability suitable for hydrostatic transmissions with closed loop circuit.
Tilting the swash plate to the opposite side of the neutral or zero displacement position
reverses ow direction.
The full-length shaft with a highly efcient tapered roller bearing arrangement offers a
high loading capacity for external radical forces.
The hydro-mechanical servo displacement control maintains the selected swash plate
position and hence pumps displacement.
Upon release of the control handle, the swash plate automatically returns to zero
position and the ow reduces to zero.
High case pressures can be achieved without leakage even at the lowest temperatures
by using suitable shaft seals.
The servo valve arrangement offers the facility to incorporate function regulators and
remote control systems.
Axial piston units are designed for easy servicing. Complete dismantling and reassembly
can be carried out with standard hand tools, and all components or sub-assemblies are
replaceable.
© 1984 -2002, Sauer-Danfoss
Sauer-Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Sauer -Danfoss reserves the
right to alter its products without prior notice. This also applies to products already ordered provided that such alterations can be made without
subsequent changes being necessary in specications already agreed. All trademarks in this material are properties of the respective companies.
Sauer-Danfoss and the Sauer-Danfoss logotype are trademarks of the Sauer-Danfoss Group. All rights reserved.
Front page: F000 249, F000 248, F000 150, F005 102
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:022-3

3
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Contents
CONTENTS Introduction and description ................................................................................................................................... 2
Model Code ....................................................................................................................................................................... 4
Recommended tools and installation .................................................................................................................. 5
List of tools necessary for minor repairs and maintenance of units of all sizes ................................... 5
Additional tools list for complete stripping of units ...................................................................................... 5
Measuring instruments ............................................................................................................................................ 5
Trouble shooting, gauge installation and information ................................................................................. 6
Start-up procedure ....................................................................................................................................................... 7
Preconditions for trouble-free operation .......................................................................................................... 7
First-time operation ................................................................................................................................................... 8
Plumbing installation (variable displac. pump - xed displac. motor) ................................................. 10
System circuit description .................................................................................................................................... 10
System maintenance ................................................................................................................................................. 11
Inlet lter (between uid reservoir and charge pump) ............................................................................. 11
Changing the oil ...................................................................................................................................................... 11
Leak test ...................................................................................................................................................................... 11
Cleanliness ................................................................................................................................................................. 11
Checking of the oil level ....................................................................................................................................... 11
Recommended oils ................................................................................................................................................. 11
Trouble shooting ......................................................................................................................................................... 12
Transmission operates in one direction only ................................................................................................ 12
System response is sluggish ................................................................................................................................ 12
Neutral difcult or impossible to nd .............................................................................................................. 13
System will not operate in either direction ................................................................................................... 13
Inspection instructions ......................................................................................................................................... 14
Checking the charge pressure ............................................................................................................................. 14
Checking the charge pump .................................................................................................................................. 14
Checking the charge check valves ...................................................................................................................... 14
Checking the servo valve (control valve) ............................................................................................................ 15
Disassembly and assembly .................................................................................................................................... 16
Sectional view .......................................................................................................................................................... 16
Exploded view .......................................................................................................................................................... 17
Minor repairs ............................................................................................................................................................. 18
Preparation for assembly ...................................................................................................................................... 18
Mounting block ...................................................................................................................................................... 18
Changing the shaft seal disassembly .................................................................................................................. 19
Changing the shaft seal assembly ....................................................................................................................... 20
Changing the charge pump and the charge check valves .............................................................................. 21
Changing the servo valve (control valve) ........................................................................................................... 23
Major repairs ............................................................................................................................................................. 24
Changing the valve and bearing plate disassembly ......................................................................................... 24
Changing the valve and bearing plate assembly .............................................................................................. 25
Changing the cylinder block kit disassembly .................................................................................................... 27
Changing the cylinder block kit assembly ......................................................................................................... 28
Changing the swash plate and servo piston disassembly ............................................................................... 29
Changing the swash plate and servo piston assembly .................................................................................... 31
Changing the pump shaft ..................................................................................................................................... 33
Installation torque values ....................................................................................................................................... 35
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:022-3

4DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Model Code
TYPE DESIGNATION AND ORDER CODE
Producer mark
A1
noitacificeps recudorp
accordin
g
to constructio
n
(at
p
resent = A1)
S P V 2 A 1
Series of
p
roduc
t
S
PV Pum
p
variabl
e
2
A
ssoc
i
at
i
on
t
y
pe 2
0
Orientation of rotation
R Right
L Left
Input port
working port SAE-flange
3 = 3000 psi SAE J518 (207 bar)
for displacement 033 - 119 cm3
6 = 6000 psi SAE J518 (414 bar)
for displacement 166 - 334 cm3
Dis
p
lacement c
m
3 [in3]
033 = 33.3 [2.03]
052 = 51.6 [3.15]
070 = 69.8 [4.26]
089 = 89.0 [5.43]
119 = 118.7 [7.24]
166 = 165.8 [10.12]
227 = 227.3 [13.87]
334 = 333.7 [20.36]
Shaft end
SAE-spline shaft 16/32
= 21 teeth for displacement 033 - 070
Z = 23 teeth for displacement 089
= 27 teeth for displacement 119 - 227
= 40 teeth for displacement 334
K* conic shaft end with toleranced key
* available on request
Units with working mark
3-letter combination e.g.:
Cxx All
s
e
a
l
s
in Vi
to
n m
a
k
e
S
p
ecial co
p
ies with or withou
t
mark of copy:
037 3-letter combination e.
g.
special nameplate
a
n
d
a
ll
sea
l
s
in Vi
to
n
Regulation
Type of regulation of 3-letter combination
001 - 999 Desi
g
nation for re
g
ulation specification
(specified by manufacturer)
RNU… Pressure regulator of zero throw
RNO… Pressure regulator Mooring
RBR… Torque limiter
RBN… Torque limiter
with regulator of zero throw
RBN… Torque limiter
with pressure re
g
ulator Moorin
g
FBA… Mobile automation for frame size 033-11
9
End cap execution
PS… With installed charge pump
AA 10. Cover plate without gear pump
Filling gear pump (2 digits according to size) - see the table
Frame size Optional PS Frame size Optional PS
033 12 18 119 19 33
052 12 18 166 33 66
070 18 12 227 33 66
089 18 12 334 66
..3 Designation for setting of charge pressure 13 bar
(other setting of charge pressure on request)
Restriction of flow volume
The entry is required if the flow volume is
adjustable at least in one direction
1. Mark (3-characters) for the branch A
2. Mark (3-characters) for the branch B
Delimitation of flow volume is set
060 for example to 60 cm3
999 maximal setting of flow volume
950 without setting of flow volume
Control
Type of control is 3-letter combination
1-9 Type variant is 1-digit number
(is specified by manufacturer)
01-99 Designation for control and connecting plate
(is specified by manufacturer)
VML 1 Mechanical-hydraulic volume control
no entry Execution with control jet
VES 3 Electro-hydraulic volume control
VED 3 Electro-hydraulic 3-position control NG 6
VHA Setting h
y
draulic volume control b
y
load control pressure
VAE 1 Connecting plate for supply and drain
of control liquid without control instrument
VAD 100 Without control instrument with segment
and with cover plate
Example of ordering:
Axial piston variable pump SPV 2,
Displacement 89,0 cm3, Orientation of rotation: right,
Input: ange 3000 psi, SAE shaft end 23 teeth,
End cap execution: with installed charge pump
Order mark: SPV 2 / 089 - R3Z - PS 183 -A1
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5
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Recommended Tools and Installation
LIST OF TOOLS
NECESSARY FOR MINOR
REPAIRS AND
MAINTENANCE OF UNITS
OF ALL SIZES
ADDITIONAL TOOLS LIST
FOR COMPLETE
STRIPPING OF UNITS
MEASURING
INSTRUMENTS
1 Circlip pliers ∅ 2 to 2.5 mm
1 Screw driver 3 mm
1 Screw driver 6 mm
1 Screw driver 9 mm
1 Plastic hammer - small
1 Pointed pliers (can also be slightly bent)
1 Torque key to 14.9 Nm [132 lbf•inch]
1 Set of ring spanners 5/16 to 11/4
1 Set of Allenkeys 1/4 to 3/8
1 Fixed spanner 15/6 for high pressure relief valve
1 Puller retainer seal
(Major repairs should not be carried out during the warranty period.)
1 Right angle screw driver 16 mm
1 Set of drifts 2 to 10 mm
1 Plastic hammer - large
1 Bearing puller 80 x 120 mm
1 Bearing puller 200 x 250 mm
1 Each xed spanner for servo cylinder 36, 41, 46, 50, 55, 60, 65 mm
1 Depth gauge 300 mm
1 Set of xed or open ended spanners 7/16 to 11/4
1 Fitting block - see page 14
At last 2 pressure gauges up to 60 bar damped (charge pressure - servo pressure)
1 Vacuum gauge to +1.0 ÷ -1.0 bar [14.5 ÷ -14.5 psi] (vacuum measurement at the charge
pump)
2 Pressure gauges to 600 bar [8700 psi] (high pressure measurement at the valve block)
1 Pressure gauge to 8 bar [116 psi] (casing pressure measurement)
Additional: Torque spanners, separate order!
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:024-5

6DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
P000 341
TROUBLE SHOOTING, GAUGE INSTALLATION AND INFORMATION
Gauge Information
A Charge Pressure 60 bar [870 psi] - Gauge
7/16 - 20 UNF O-ring Fitting
B System Pressure 600 [8700 psi] bar - Gauge
7/16 - 20 UNF O-ring Fitting
C Inlet Vacuum Vacuum gauge
Tree Into Inlet Line
D Case Pressure 8 bar [116 psi] - Gauge
Adapt to Bottom Drain Port
Recommended Tools and Installation
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:026-7

7
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Start-up procedure
PRECONDITIONS FOR
TROUBLE-FREE
OPERATION
Cleanliness: Ensure that the pipes, pipe connections and hoses as well as all other
components are completely clean.
Ventilation and venting of the oil reservoir via an air lter.
Operating uid: HLP uid according to DIN 51524, ATF type A SUFFIX A, HD-SAE motor
oils, see Fluid Manufacturers, Technical Information.
Oil level: (The inlet pipe and return ow port must always be below the surface of the
oil). No funnel-shaped eddying at the inlet connection pipe. No formation of foam at
the return ow pipe. The inlet connection pipe must be substantially above the bottom
of the reservoir. A partition plate should be located between the inlet and return ow
connection pipes.
Filtration: Filtration grade = 10 µm [394 µinch] nominal.
Inlet pressure of charge pump: 0.85 bar [12.3 psi] absolute (- 0.15 bar [-2.2 psi]) with a
new lter element and at an operating temperature of approx. 50 °C [122 °F].
A charge pump inlet pressure less than 0.75 bar [10.9 psi] absolute (-0.25 bar [-3.6 psi]) is
permissible for a short time with a reservoir temperature of less than 50 °C [122 °F] on a
cold start in order to warm up the system under no-load.
If frequent cold starts are to be made, the system should be warmed up by a reservoir
heater.
If the charge pump inlet pressure is less than 0.75 bar [10.9 psi] absolute (-0.25 bar [-3.6
psi]) on operating temperatures higher than 50 °C [122 °F], the lters must be changed.
A charge pump inlet pressure of less than 0.5 bar [7.3 psi] absolute (- 0.5 bar [-7.3 psi])
is not permissible.
The lter requires changing or the operating temperature is too low.
Venting the pump and motor housing as well as the connection lines and other
components.
The return ow to the oil reservoir must be free of bubbles. After venting the system,
check the uid level and ll to proper level if necessary.
Carry out a leak test on the transmission (inlet line, lter, pipe and hose lines, valves,
control elements, pump and motor) giving due consideration to the service life of the
transmission, environmental protection and the reduction of oil consumption.
Tighten up any leaking joints and other connections while the system is not under
pressure.
Pressure uid temperature range: min. = -40 °C [-40 °F], max. = 95 °C [203 °F].
Viscosity range:
max. = 1000 mm2/s [4630 SUS*] (cSt) (for a short time only on a cold start).
min. = 7 mm2/s [49 SUS*] (cSt).
Recommended viscosity range: 12-60 mm2/s [66-278 SUS*] (cSt).
*SUS (Saybolt Universal Second)
Changing the oil: The oil should be changed after max. 80-100 hours of operation, but at
the latest one year after rst-time operation.
The second oil change should be after max. 500 hours of operation but at the latest one
year after the rst change of uid.
Thereafter, the oil should be changed every 1000 hours of operation but at least once a
year. It is not permissible to mix oil.
Renew the inlet lter each time the oil is changed or when the inlet pressure of the
charge pump falls below the permissible tolerance.
Clean the air lter whenever too much dirt has accumulated.
The max. speed is as specied in the catalogue Series 20 Axial Piston Pumps, Technical
Information or Series 20 Axial Piston Motors, Technical Information.
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:026-7

8DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Start-up procedure
PRECONDITIONS FOR
TROUBLE-FREE
OPERATION (continued)
FIRST-TIME OPERATION
The charge pressure measured at the charge pressure gauge connection port of the
pump with the adjusting lever in the neutral position should be approx. 15 bar [217.6 psi]
at a pump input speed n = 1500 min-1 (rpm).
The charge pressure measured at the charge pressure gauge connection port of the
pump with the adjusting lever engaged should be approx. 2 bar lower at a pump input
speed n = 1500 min-1 (rpm).
1. After installing the transmission and the corresponding pipeline connections,
remove the plug from the charge pressure gauge port of the variable displacement
pump. Fit a gauge with a measuring range up to 60 bar [870 psi] to this port.
The charge pressure gauge port has a straight 7/16-20 UNF-2 B SAE thread.
2. Disconnect the charge pump inlet line from the charge pump inlet connection pipe.
3. Fill the pump case and the motor case with the recommended oil through the drain
port.
4. Fill the oil reservoir with uid. As soon as oil emerges from the end of the discon-
nected charge pump inlet line tighten the pipe connector (see table to page 35 for
the correct tightening torque) and continue to ll the reservoir.
Only use oil reservoirs that are tted with air lters.
5. Disconnect the control linkage from the control handle. The pump must be in the
zero position.
6. Allow the prime mover to turn for approx. 15 sec. by using the starter.
6A. If the prime mover is an electric motor: Switch on and off again.
7. Then start the prime mover and allow the pump to turn at idling speed (approx. 750
min-1) for approx. 5 minutes.
7A. In the case of electric prime mover: Allow to turn for approx.1 minute.
After initial uctuations in pressure, the charge pressure should settle down to 10 bar
[145 psi] or 12 bar [174 psi].
8. Check the pressure uid level.
9. Raise the speed to approx. 1500 min-1 (rpm). The gauge should now indicate a pres-
sure of approx. 15 bar [217.6 psi].
10. If the charge pressure falls to below 8 bar [116 psi], stop the prime mover, nd
the fault in accordance with the trouble-shooting guide and take the appropriate
remedial action.
11. Stop the prime mover and attach the control linkage to the control handle. Check the
uid level in the sight glass and ll to proper level if necessary.
12. Restart the prime mover and, under no-load, adjust the zero position by means of the
control handle - or even better by the control linkage - so that in both directions nal
position of stroke per Series 20 Axial Piston Pumps, Technical Information is achieved.
13. Allow the prime mover to turn at 1500 min-1 (rpm). The charge pressure should now
be 15 bar [217.6 psi].
14. Slowly move the control handle backwards and forwards. If the pump is working
properly, the charge pressure drops by about 2 bar [29 psi] from the value stated in
step 13 above as the control handle initiated.
15. Allow the system to work under full load with a pump speed of approx.1500 min-1
(rpm). It must be possible to achieve the values stated in steps 13 and 14 above.
16. Check all joints and connections for leaks.
17. Stop the prime mover. Remove the gauge from the connection port. Replace the
7/16-20 UNF-2 B plug and tighten with the tightening torque stated in the table to
page 35.
Check the pressure uid level in sight glass of the reservoir and ll to proper level
if necessary.
The system is now ready for operation.
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:028-9

9
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Start-up procedure
P000 337E
Gauge port -
servo cylinder pressure
(both side)
Control handle
Gauge port "M":
Charge pressure
Port "S":
Suction port
(charge pump)
Port "A"+"B":
High pressure
Case drain
p
orts
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:028-9

10 DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
P000 341
PLUMBING INSTALLA-
TION (VARIABLE
DISPLACEMENT PUMP -
FIXED DISPLACEMENT
MOTOR)
SYSTEM CIRCUIT DESCRIPTION
HEAT EXCHANGER BYPASS VALVE
RESERVOIR
VACUUM GAUGE
HEAT EXCHANGER
OUTPUT SHAFT
MOTOR SWASHPLATE
FIXED
DISPLACEMENT MOTOR
LOOP FLUSHING VALVE
PURGE RELIEF VALVE
CHARGE PRESSURE
RELIEF VALVE
SERVO
PRESSURE
RELIEF VALVES
SERVO CONTROL CYLINDER
SERVO CONTROL CYLINDER
PUMP SWASHPLATE
REVERSIBLE VARIABLE
DISPLACEMENT PUMP
CONTROL
HANDLE
INPUT SHAFT
WORKING LOOP (LOW PRESSURE) SUCTION LINE CASE DRAIN FLUIDCONTROL FLUIDWORKING LOOP (HIGH PRESSURE)
P000 027E
Start-up procedure
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:0210-11

11
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
The lter element must be exchanged as soon as the pressure drops below 0.75 bar
[10.9 psi] absolute (-0.25 bar [-3.6 psi]) when the transmission is at normal operating
temperature. The lter must also be exchanged each time the pressure uid is changed.
Filtration grade = 10 µm [394 µinch] nominal.
Under normal operating conditions, the oil should be changed at the following intervals:
The rst oil change should be carried out after max. 80-100 hours of operation but at the
latest one year after rst-time operation. The second change should take place after max.
500 hours of operation but at the latest one year after the rst change.
Thereafter, the oil should be changed at least every 1000 hours of operation or at least
once a year.
To change the oil, the used uid must be drained off when the system is at operating
temperature! Remove any residual dirt or sludge from the reservoir!
In extremely dusty atmospheres, the intervals between oil changes must be correspon-
dingly shortened.
Oil samples should be taken every 500 hours of operation. To do this, take approx. 0.5l
of oil from a point on a level with the inlet (suction) connection. Fill the sample into a
closable container that is free of residues.
Have the oil examined for serviceability by Sauer-Danfoss, by Oil Manufacturer or by an
appropriate institution.
Important: Use only recommended oils! (See Fluid Manufacturers, Technical Information).
It is not permissible to mix oils.
Carry out a leak test on the transmission (inlet line, lter, pipe and hose lines and connec-
tions, valves, control elements, pump and motor) giving due consideration to the service
life of the transmission, environmental protection and reduction of oil consumption.
Tighten up any leaking joint and other connections while the system is not under
pressure.
Make certain that the air lter for ventilation of the oil reservoir is regularly cleaned,
since the input pressure may be affected if it is dirty. If there is an oil cooler, the cooler
surface should be kept free from contamination. On units which have hose couplings
on the connecting pipes, contamination of any sort must be avoided. Cotton rags or lint
cleaning cloths may not be used for cleaning. Use only lint-free materials.
When changing the oil, be sure the area around the ller cap is free from foreign objects.
The oil, which can be kept clean by using a lter cloth, should be added by means of
a clean funnel.
The level of the oil should be checked daily using the gauge glass. In case of loss of oil,
the leak must be rectied.
Important: Use only recommended uids! (See Fluid Manufacturers, Technical Informa-
tion.) It is not permissible to mix.
HLP - hydraulic uids according to DIN 51524
ATF - automatic transmission uids type A, SUFFIX A
HD - SAE motor oils
INLET FILTER (BETWEEN
FLUID RESERVOIR AND
CHARGE PUMP)
CHANGING THE OIL
LEAK TEST
CLEANLINESS
CHECKING OF THE OIL
LEVEL
RECOMMENDED OILS
System Maintenance
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:0210-11

12 DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
TRANSMISSION
OPERATES IN ONE
DIRECTION ONLY
Trouble Shooting
Check control
linkage
Repair
or replace
Inspect high pressure
relief valve
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
Insert charge
check valves
(see page 14)
Repair
or replace
(see page 21,22)
Inspect shuttle valve
in valve block
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
Repair or replace
the valve block
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
OK
Defective Defective
OK OK
Inspect control valve
(see page 15)
Replace control valve
(see page 23)
Defective
Defective Defective
OK
Repair or replace
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
SYSTEM RESPONSE IS SLUGGISH
Check charge
pressure
(see page 14)
Inspect
control valve
(see page 15)
Inspect motor
by-pass valve
(if used)
Replace
control valve
(see page 23)
OK
Defective
OK
OK
Repair
or replace
Defective
Replace
transmission
(pump + motor)
OK
Inspect charge
pressure
relief valve
(see page 14)
Repair
or replace
(see page 21, 22)
Inspect purge
relief valve at motor
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
Inspect charge
pressure
relief valve
(see page 14)
Repair or replace
the valve block
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
Defective Defective
Repair
or replace
(see page 21, 22)
Defective
Inspect
inlet filter
OK OK
Replace
Clogged
Inspect
charge pump
(see page 14)
Repair
or replace
(see page 21, 22)
Defective
to low
in
neutral
to low in neutral and
forward or reverse
to low inforward
or reverse
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:0312-13

13
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
NEUTRAL DIFFICULT OR IMPOSSIBLE TO FIND
SYSTEM WILL NOT OPERATE IN EITHER DIRECTION
Trouble Shooting
Check control
linkage
Repair
or replace
Inspect control valve
(see page 15)
Replace
pump
Replace control valve
(see page 23)
OK OK
Defective Defective
Check fluid
level in
reservoir
Check control
linkage
Inspect motor
by-pass valve
(if used)
Repair
or replace
OK
Defective
OK
Fill to
propper level
to low
Repair
or replace
Defective
Check charge
pressure
(see page 14)
OK
Inspect
charge pump
(see page 14)
Inspect
inlet filter
Repair
or replace
(see page 21, 22)
Defective
Replace
Defective
Inspect charge
pressure
relief valve
(see page 14)
Repair
or replace
(see page 21, 22)
Clogged
Inspect purge
relief valve at motor
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
Repair or replace
the valve block
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
Defective
Replace
transmission
(pump + motor)
Inspect
control valve
(see page 15)
Replace
control valve
(see page 23)
Defective
Inspect motor
by-pass valve
(if used)
Repair
or replace
Defective
Check system
pressure
(see Series 20 Axial Piston
Motors, Service Manual
and Repair Instruction)
to low in
neutral and
forward or
reverse to low in
forward or
reverse
to low in
neutral
OK
OKOK OK
OK OK OK
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14 DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Checking the charge pressure
Checking the charge pump
Checking the charge check valves
1. Remove charge pump to examine
check valves (see page 21).
Trouble Shooting
1. Clean the charge pressure gauge
connection on the pump.
2. Pressure gauge (see recommended
measuring instruments) to be
connected.
3. Set operating speed at 1500 min-1
4. Charge pressure with the pump in
neutral ca. 15 - 18 bar [218 - 261
psi]. When the pump in forward or
reverse the charge pressure should
be at a two bar lower level (purge
relief valve, motor).
1. Inspect if contamination is holding
the valve open and for galling or
wear on valve cone and seat and
inspect for broken spring.
2. The shaft and gear teeth must work
freely.
3. Further disassembly of the charge
pump is not permitted.
2. Check the spring pressure and for
correct operations. Check if conta-
mination may be prohibiting free
movement of the ball.
INSPECTION
INSTRUCTIONS
F000 077
F000 078
F000 079 F000 080
Hex-plug, Spring 3
Shims Valve cone
5+6 10 5+6
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15
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
1. Disconnect the external control
linkage from the control handle and
check for neutral operating with
control handle. Releasing control
handle should allow the pump to
return to neutral. If operation is satis-
factory with external control linkage
disconnected, the problem is not in
the hydrostatic transmission.
If operation is not satisfactory with
external control linkage disconnec-
ted from control handle, the control
may be misadjusted.
3. Holding the control in place, and
swing it away from housing and
remove. Inspect visible linkages, tor-
sion spring, and O-rings. Inspect for
missing, plugged, or incorrect orice.
Checking the servo valve (control valve)
Trouble Shooting
2. Remove the cap screws (see page 22).
4. Further disassembly of servo valve is
not permitted.
INSPECTION
INSTRUCTIONS
F000 082
F000 083
F000 046 F000 062
86 89, 90 82
86 78 Orice (81) 81 85 80 86 87 88
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16 DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Disassembly and Assembly
SECTIONAL VIEW
Input shaft
Swash plate Control handle Servo valve (control valve)
Charge pump
Charge check valve
Servo cylinder
Cylinder block assembly
Shaft seal
P005 121E
Axial piston variable displacement pump
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:0316-17

17
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Description of parts:
1 Hexagonal screw 28 Piston assembly 65 Hexagonal screw
2 Washer 29 Thrust plate 66 Washer
3 Charge pump assembly 30 Screw 67 Trunnion
4 Gasket charge pump 31 Sleeve retainer 68 Shim pack
5 Valve check 32 Servo sleeve complete 69 O-ring
6 O-ring 33 O-ring 70 Bearing
7 Hexagonal screw 34 O-ring 71 O-ring
8 Hexagonal screw 35 Screw 75 O-ring
9 Washer 36 Washer 77 Ring retaining
10 End cap 37 Spring guide 78 Gasket
11 Shim 38 Servo spring 80 O-ring
12 Gasket 46 Pin 81 Orice
13 Bearing 47 Locking washer 82 Kit control valve
14 Cylindrical pin 48 Connecting link 85 Spacer control servo
15 Valve plate 49 Shaft 86 Handle control handle
16 Bearing plate 50 Bearing 87 Lock washer tooth
17 Bearing plate pilot ring 51 Gasket 88 Nut hex
18 Ring retaining 52 Cylindrical pin 89 Washer
19 Retainer spring 53 Cover 90 Hexagonal screw
20 Spring guide 54 Washer 102 Hexagonal screw
21 Spring 55 Hexagonal screw 121 Orice
22 Spring seat 59 O-ring 125 Orice
23 Retainer spring 60 Plug 135 Swash plate complete
24 Cylindrical pin 61 Expander 145 O-ring
25 Cylinder block 62 Housing 146 O-ring
26 Retainer guide 63 O-ring 198 Cylinder block kit
27 Slipper retainer 64 Cylindrical pin 199 Shaft seal kit
EXPLODED VIEW
P005 113
Disassembly and Assembly
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18 DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Ø10 Pin
[Ø0.394]
70
[2.756]
5x45˚
20
[0.787]
10
[0.394]
ca. 5 mm Chamfer
[ca. 0.2 in]
Ø130
[Ø5.118]
165
[6.496]
250
[9.843]
250
[9.843]
P005 112E
The areas of repair indicated may be serviced, following the procedures in this manual,
without invalidating the warranty.
Preparation for assembly
When using a lifting device, the hooks at the end of the slings, are to be fastened in the
rings tted at the front and rear of the motor body. It is recommended that an mounting
block should be used in order to facilitate a professional operation.
Mounting block
Disassembly and Assembly
F000 084
MINOR REPAIRS
F000 085
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19
DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Disassembly and Assembly
MINOR REPAIRS
CAUTION!
These parts can be easily
damaged. Use care in
handling.
Each part should be
inspected separately if
parts are to be reused.
Always replace the O-rings.
Lubricate the small O-ring
with petroleum jelly and
insert into the I. D. of the
bronze rotating ring.
Lubricate the large O-ring
and place the O. D. of the
seal-stationary.
The seal-stationary is removed next. It
is held in place by the friction of the
O-ring on its O. D. Remove seal-stationary
with the help of a seal puller to prevent
damage to outer edge.
It is recommended that all shaft seal
parts be replaced. If parts are to be
reused, they must be protected from
being damaged by the shaft during
removal. Remove the large retaining ring
located on the shaft end of the pump.
Remove the side opposite the tangs from
the groove rst.
The rotating seal ring (bronze ring) is also
held in its position by the O-ring. It can
be removed with the help of two screw
drivers.
F000 086
F000 088
F000 087
Changing the shaft seal (disassembly)
77
71 Bronze ring
77 75 Seal-
stationary
77 Clamp seal puller
on seal-stationary
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:0318-19

20 DKMH.PS.315.B1.02 520L0535
Series 20 – Axial Piston Pumps
Service Manual and Repair Instructions
Changing the shaft seal (assembly)
Disassembly and Assembly
MINOR REPAIRS
(continued)
CAUTION!
Protect parts from damage
by the shaft.
Slide seal-stationary into place against
the bronze sealing ring.
Slide the bronze sealing ring over the
shaft and onto the shaft pilot diameter
with the O-ring facing the unit. Work the
ring into place using hand force only.
Compress the seal-stationary to expose
the retaining ring groove. Install the
retaining ring with the beveled side
out, putting the side opposite the tangs
into the groove rst. Be certain that
the retaining ring has snapped into the
groove completely.
F000 089
F000 213
F000 091
F000 090
71 Bronze ring
Seal stationary
77 Clamp seal puller
on seal-stationary
77
Series 20 Axial Piston Pumps_SR.indd 24.4.2002, 14:0320-21