Parker Hydraulics Hydraguide HGF Series Manual

Service Manual 2753
HGF Series Service Procedure
Hydraulic Pump/Motor Division
Hydraguide™
Hydrostatic Steering System
Hydraulics

HGF Design Features Illustration
Port Cover
Hex Drive Assembly
Port Manifold
Isolation Manifold
Metering Ring
Rotor Set
Upper Cover Plate
Valve Springs
Valve Set
Drive Link
Commutator Set
Drive Plate
Thrust Bearing
Upper Cover & Jacket
Tube Assembly Set
Input Shaft/WheelTube

The model HGF Hydraguide™ power steering unit is Ross' most recent addition to its series of hydrostatic
steering products. The HGF combines several advanced features designed to meet industry's needs for improved
steering of its construction, industrial, and agricultural vehicles.
• An ultra compact and light weight package designed for easy installation with fluid connections at the lower end of
unit.
• An open center fast response rotary plate type valve (spring centered) with options of open or closed cylinder ports
and "power beyond".
• Small eccentric rotor set provides smooth operation.
• Lower optional noise levels.
• Column (jacket tube) and input shaft/wheel tube integral to unit for improved column/unit alignment. Lengths tailored
to user requirements.
For operation, the HGF system requires the following components:
• an engine-driven pump,
• a relief valve,
• a cylinder or cylinders,
• a reservoir and filter,
• suitable fluid lines or hoses, and
• the HGF hydrostatic unit.
The driver has power steering control at all times, so long as system components work together, system integrity
is maintained, and adequate fluid is present. If there is a failure in the high-pressure circuit, a loss of power steering
will result. The HGF, however, is designed to have some manual steering capability, depending on the installation. If
you can't manually steer the vehicle without using extraordinary measures, such as leaving your seat, or pushing with
your legs, don't try it. Some vehicles may be impossible to steer manually because of their weight and size. Repair
the failure in the power circuit.
HGF Design Features
Hydraguide™
WARNING: SUCH EXTRAORDINARY MEASURES SHOULD NOT BE USED IN ATTEMPTING TO MANUALLY
STEER THE VEHICLE, AS THEY MAY GENERATE FORCES IN EXCESS OF 125 FT. LBS. (169 N m),
THEREBY DAMAGING THE UNIT INTERNALLY, WHICH COULD RESULT IN A COMPLETE LOSS OF
STEERING.
i

WARNING: ALL STEERING MECHANISMS ARE LIFE AND LIMB ITEMS. AS SUCH, IT IS
IMPERATIVE THAT THE INSTRUCTIONS IN THIS BOOKLET ARE FOLLOWED TO THE LETTER.
FAILURE TO OBSERVE THE PROCEDURES SET OUT IN THIS PAMPHLET MAY RESULT IN LOSS
OF STEERING.
HGF Series Service Procedure
Table of Contents
Page
Definitions.....................................................................................................................................................1
Introduction...................................................................................................................................................2
Design and Operation...................................................................................................................................3
HGF Hydraguide Steering System .............................................................................................................. 4
Troubleshooting Guide................................................................................................................................. 5
Troubleshooting Checklists...........................................................................................................................6
Component Alignment Groove Illustration (Fold-Out) ................................................................................7B
Exploded View (Fold-Out) ......................................................................................................................... 7C
Tools and Material Required for Servicing....................................................................................................8
Torque Chart.................................................................................................................................................8
Disassembly and Inspection.........................................................................................................................9
Assembly....................................................................................................................................................21
Hydraulic Fluid........................................................................................................................................... 36
Filling and Air Bleeding the System............................................................................................................36
Tips for Maintaining the System ................................................................................................................ 37
Warnings for Proper Steering System Operation .......................................................................................37
ii

1
HGF Series Service Procedure
NOTE: A NOTE provides key information to make a procedure easier or quicker to
complete.
CAUTION: A CAUTION refers to procedures that must be followed to avoid damaging the HGF
or other system components.
Disclaimer
This Service Manual has been prepared by Ross for reference and use by mechanics who have been trained to repair
and service steering components and systems on commercial and non-commercial vehicles. Ross has exercised
reasonable care and diligence to present accurate, clear and complete information and instructions regarding the
techniques and tools required for maintaining, repairing and servicing the complete line of Ross HGF "Hydraguide"
Hydrostatic Steering Units. However, despite the care and effort taken in preparing this general Service Manual, Ross
makes no warranties that (a) the Service Manual or any explanations, illustrations, information, techniques or tools
described herein are either accurate, complete or correct as applied to a specific HGF steering unit, or (b) any repairs
or service of a particular HGF steering unit will result in a properly functioning steering unit.
If inspection or testing reveals evidence of abnormal wear or damage to the HGF steering unit or if you encounter
circumstances not covered in the Manual, STOP–CONSULT THEVEHICLE MANUFACTURER'S SERVICE MANUAL AND
WARRANTY. DO NOT TRY TO REPAIR OR SERVICE AN HGF STEERING UNIT WHICH HAS BEEN DAMAGED OR
INCLUDES ANY PART THAT SHOWS EXCESSIVE WEAR UNLESS THE DAMAGED AND WORN PARTS ARE
REPLACED WITH ORIGINAL EQUIPMENT REPLACEMENT AND SERVICE PARTS AND THE UNIT IS RESTORED TO
ORIGINAL EQUIPMENT SPECIFICATIONS FOR THE HGF STEERING UNIT.
It is the responsibility of the mechanic performing the maintenance, repairs or service on a particular HGF steering
unit to (a) inspect the steering unit for abnormal wear and damage, (b) choose a repair procedure which will not
endanger his/her safety, the safety of others, the vehicle, or the safe operation of the vehicle, and (c) fully inspect and
test the HGF steering unit and the vehicle steering system to insure that the repair or service of the steering unit has
been properly performed and that the steering unit and system will function properly.
Definitions
WARNING: A WARNING REFERS TO PROCEDURES THAT MUST BE FOLLOWED FOR THE
SAFETY OF THEVEHICLE DRIVER AND THE PERSON INSPECTING OR
REPAIRING THE HGF.

2HGF Series Service Procedure
Introduction
Service Manual for Model HGF
This service manual has one purpose: to guide you in maintaining, troubleshooting, and servicing the HGF
Hydraguide power steering valve.
Material in this manual is organized so you can work on the HGF and get results without wasting time or being
confused. To get these results, you should read this entire manual before you being any work on the HGF.
The next section of this manual, Design and Operation, treats the major parts of the HGF and explains how they
function together. The knowledge you acquire from reviewing this section should assist you in solving your steering
problem.
This manual also contains troubleshooting information and checklists. With them, you can diagnose a steering
problem without removing the HGF from the vehicle. If you must service the HGF, the checklists will help you to
determine where the problem may be.
The three-column format of the Disassembly and Inspection, and Assembly sections will make it easier for you to
service the HGF. Column 1 gives a brief key for each procedure. Column 2 explains in detail the procedure you
should follow. Column 3 illustrates this procedure with photographs. Pay special attention to the notes, cautions, and
warnings.
A fold-out page with an HGF Hydraguide exploded assembly view is provided in this manual. The component part
names and item numbers assigned on this exploded assembly view correspond with names and item numbers (in
parentheses) used in the disassembly and assembly procedures set forth in this manual. When this exploded
assembly view page is folded out, you can easily identify components and locate their relative position on the
exploded assembly view as you follow the disassembly and assembly procedures.
As you gain experience in servicing the HGF, you may find that some information in this manual could be clearer or
more complete. If so, let us know about it. Don't try to second guess the manual; if you are stuck, contact us.
Servicing the HGF should be a safe and productive procedure, in order for the unit to deliver the reliable, long-life
operation engineered into it.

3
HGF Series Service Procedure
Satisfactory performance of the overall hydraulic system
requires a well-engineered installation. The hydraulics
must meet the design features of the vehicle and
contribute to the operation for which the vehicle was built.
Make no changes to the steering system without first
consulting qualified factory service personnel. Ross
Gear extends engineering advice and welcomes
requests for assistance.
Engineering contacts can provide information on such
hydraulic components as pumps, cylinders, and fluid
lines. The HGF control unit works best with a balanced-
area cylinder design.
HGF: Design
The HGF Hydraguide unit consists of a fluid control valve
section and a fluid metering section. These are
hydraulically and mechanically interconnected inside the
unit.
ControlValve Section: Operation
The HGF Hydraguide uses a servo-reactive (feedback
control) valve which is centered by two sets of three coil
springs. The valve regulates pressure and directs pump
flow to the steering cylinder or cylinders. The valve is of
the open-center type: when in the neutral position, it
allows fluid to flow from the pump to the pressure port,
through the HGF unit to the return port, and back to the
reservoir.
The valve is available in open- or closed-cylinder
configurations, each of which brings its own advantages
to bear in the hydraulic system.
Open Cylinder: cylinder ports are open to the metering
pump, allowing road or ground reaction to rotate and
recenter the valve, as the vehicle's steering geometry
provides recentering forces. When the driver completes
a turn, the steering will recenter, as happens, for
example, in most automobile power steering systems.
Closed Cylinder: cylinder ports are blocked to the
metering pump, preventing road or ground reaction from
rotating and recentering the valve. The driver must steer
to "straight ahead" or another position. This design is
useful in a vehicle which must remain turned while the
driver takes his hands off the steering wheel to operate
other controls.
Metering Section: Operation
The metering section performs three functions:
• It meters (measures) fluid to the cylinder or cylinders:
• It maintains the ratio of hand wheel turns to the
direction of the steered wheels; and
• It acts as a pump for manual steering in the event high-
pressure fluid does not reach the HGF unit.
HGF: Design and Operation
(See HGF Design Features and Design Illustration)

4HGF Series Service Procedure
OPEN CENTER
HYDRAGUIDE™STEERING POWER BEYOND
HYDRAGUIDE™STEERING
HGF Hydraguide™ Steering system
Return
Pressure

5
HGF Series Service Procedure
Preparation
Make your troubleshooting easier by preparing as
follows:
• work in a clean, well-lighted place;
• have proper tools and materials nearby:
• have a space set aside where you can lay components,
parts, and tools; and
• have an adequate supply of clean petroleum-based
solvent.
WARNING: SINCE THEY ARE FLAMMABLE, BE
EXTREMELY CAREFUL WHEN USING ANY SOLVENT.
EVEN A SMALL EXPLOSION OR FIRE COULD CAUSE
INJURY OR DEATH.
WARNING: WEAR EYE PROTECTION AND BE SURE
TO COMPLY WITH OSHA OR OTHER MAXIMUM AIR
PRESSURE REQUIREMENTS.
Preliminary Checks
For all their complexity, hydraulic systems are often
trouble-free. The steering problem an operator
complains of could be caused by something other than
the hydraulic components.
Thus, once you have determined the problem and test
driven the vehicle (if possible), start with the easy-to-
check items.
On some vehicles, the conditions of the tires, especially
on the steered wheels, may affect steering. Make sure
pressures are at manufacturer's specifications. Make
sure tires are balanced and that they show no signs or
damage or severe wear. Check that they are mounted
properly.
Check steering and front end linkage. Broken, loose, or
binding parts could cause certain steering problems.
See if something in the steering column is loose or
binding.
If belts are present, check all of them. A tight belt could
also be glazed and a slipping belt doesn't always squeal.
In addition, the following could also contribute to a
steering problem:
• an overloaded vehicle;
• parts damaged from impact not properly repaired, or
that should have been replaced; and
• improper replacement parts.
Hydraulic Components
If you think the problem is caused by a hydraulic
component, start by checking the easy-to-reach items.
Check all hoses and lines for cracks, hardening, or other
signs of wear. Reroute any usable hoses that are kinked,
severely bent, or that rest against hot engine parts. Look
for leaks, especially at couplings. Replace any hoses or
lines that don't meet system flow and pressure ratings.
Next, go to the reservoir and filter or filters. Check fluid
level and look for air bubbles. Examine the filter; if it's
clogged, follow manufacturer's instructions for cleaning or
replacing it. A filter with a minimum 25 micron filtration is
recommended for the HGF system.
Visually check other components to see if they are
loosely mounted, show signs of leaks, or other damage
or wear.
It may be necessary that you perform hydraulic tests on
the pump and other hydraulic components. To do so,
consult the manuals published by the vehicle or
component manufacturers.
Troubleshooting Guide
NOTE: Before troubleshooting a steering problem, check service literature published by the
vehicle and component manufacturers. Follow their instructions, if given, for
checking any component but the HGF Hydraguide unit.

6HGF Series Service Procedure
Troubleshooting Checklists
1. NOISE
NORMAL NOISE
A low hissing from the HGF control valve section during a turn
A noise from the system relief valve when it is actuated
Pump growl from some types of power steering pumps
ABNORMAL NOISE
A squealing noise during a turn may indicate that the belt or belts should be tightened or replaced
A clicking noise during a turn may indicate that some component is loose and shifting under load.
II. POSSIBLE STEERING PROBLEMS AND CAUSES
STEERINGWANDER
Different size tires
Tire pressure incorrect or unequal left to right
Loose or worn steering linkage parts
Improperly adjusted or worn wheel bearings
In some vehicles, front end out of alignment
NO RECOVERY FOR OPEN-CYLINDER UNIT
Tire pressure low
Steering linkage parts binding
Tight front axle kingpins
Steering column binding or misaligned
SHIMMY
Improperly mounted tire or wheel
Components in steering linkage loose, worn, or out of adjustment
Wheels or brake drums out of balance
Wheel bearings improperly adjusted
Air in the hydraulic system
HIGH STEERING EFFORT IN ONE DIRECTION
Vehicle overloaded
Low hydraulic system pressure
Excessive system heat causing HGF plate valve to stick. See checklist under Excessive Heat.

7A
HGF Series Service Procedure
HIGH STEERING EFFORT IN BOTH DIRECTIONS
Different size tires
Vehicle overloaded
Low hydraulic fluid level
Low flow or pressure from pump
Components in steering linkage binding
Restriction in fluid return line, or line too small
LOST MOTION (LASH) ATTHE STEERING WHEEL
Steering wheel loose on column
Components in steering linkage loose or worn
HGF unit loose at mounting
Air in hydraulic system
EXCESSIVE HEAT [200° F MAXIMUM (93.3°)]
Undersized replacement hose or line
Kinked or severely bent hose or line
Restricted oil coolers
Restricted recentering of HGF unit
Excessive fluid flow
WARNING: IF THE HYDRAULIC SYSTEM FLUID BECOMES OVERHEATED [IN EXCESS OF 200°F (93.3° C)],
SEALS IN THE SYSTEM CAN SHRINK, HARDEN, OR CRACK, THUS LOSINGTHEIR SEALING ABILITY.

7B
HGF Series Service Procedure
HGF COMPONENT ALIGNMENT GROOVE ILLULSTRATION
COMPONENTS OFTHE HGF UNITWITH ALIGNMENT GROOVES MUST BE
ASSEMBLED SOTHATTHEIR ALIGNMENT GROOVES ARE POSITIONED AS
ILLUSTRATED FORTHE UNIT
TO FUNCTION CORRECTLY
IFTHE HGF UNIT BEING DISASSEMBLED HAD A CONTACT
BRUSH ASSEMBLY, NOTETHE RADIAL POSITION OF IT'S
HOLE RELATIVETO ALIGNMENT GROOVED SIDE OFTHE
UNIT BEFORE DISASSEMBLY AND REASSEMBLE INTHE
SAME RADIAL POSITION.

7C
HGF Series Service Procedure
HGF Exploded Assembly View-Typical
Item Number Description
1 Nut 5/16 UNF 24 (4)
2 Port Cover
3 Seal Ring (5)
3A Seal Ring (White)
4 O’Ring (3), (4) or (5)
5 Ball-7/32 inch (6mm) dia.
5A Relief valve cartridge
5B Coil spring
6 Plug
6A Hex plug
7 O’Ring, Plug & O’Ring assy.
7A O’Ring
8 Port Manifold
9 Spring, 3/4 inch (19mm) (3)
10 Hex Drive assy.
11 Alignment Pin (Needle Brg.) (9)
12 Valve Ring
13 Valve Plate
14 Spring, 1/2 inch (13mm) (3)
15 Isolation Manifold
16 Drive Link
17 Metering Ring
18 Screw, Hex Socket Hd (11)
19 Seal, Commutator
20 Commutator Cover
21 Commutator Ring
22 Commutator
23 Spacer–Drive Link
24 Rotor
25 Stator
26 Drive Plate
27 Spacer–Thrust Bearing
28 Thrust Bearing
29 Face Seal
31 Seal Spacer
32 Upper Cover Plate
33 Input Shaft/Wheel Tube
34 Retaining Ring
35 Washer–Retaining Plate
36 Retaining Plate
37 Upper Cover & Jacket Assy.
38 Bushing
39 Seal
40 Special Bolt, 5/16 24UNF-2A
41 Nut
42 Screw
43 Contact Ring Assy.
44 Contact Brush Assy.
45 Screw & Lock Washer
46 Washer [for 1-3/4 inch (45mm)
Jacket]
47 Horn Wire Cable Assy.
51 Spacer [for 1-1/2 inch (38 mm)
Jacket]
52 Ball 9/32 inch (22mm)
Items # 44, 45,46, 51 are not part of HGF service
assembly unit.They must be purchased as
separate items of order.
Matched Set
}
}
}
Matched Set
Rotor Assy– Matched Set

7D HGF Series Service Procedure
20
Commutator Cover
HGF 014001
28
Thrust Bearing
069020
34
Retaining Rings
401465
35
Washer
028493
38
Bushing
063042
39
Seal Dust
402405 All other column parts per specification.
3
032755 (5)
( )
3A
032832 4 032758 (5) 7 032645 7A 032750 19
032724
29
478046
Seal Kit
SK 000097
29
Face Seal
032763
30
Back-up Ring
032770
31
Seal Spacer
477297
32
Upper Cover Plate
HGF 016012
21-22
Commutator-Commutator Ring
HGF 014002 A1
26
Drive Plate
HGF 013000
27
Spacer Thrust Bearing
4773000
Use with HGF Assembly View–Typical
1
Nut 5/16 UNF (4)
G103025
4
“O”Ring (5)
032758
15
Isolation Manifold
HGF 015000
16
Drive Link
HGF 013002
19
Seal Commutator
032724
5
Ball 7/32 dia.
G453569
6-7
Plug and “O” Ring
415585-A1
9 & 14
Spring Kit
401443X1
(3) 401443
(3) 401608
10
Hex Drive Assy
HGF 013001 A1
11
Alignment Pin
040147 X1
12-13
Valve Ring-Valve Plate Matched Set
HGF 014000 A1
3A
Seal Ring (White)
032832
3
Seal Ring
032755 (5)
2-8
Port Cover & Port Mainfold Kits
HGF 016015 X1(5 line) HGF 016016X1 (4 line)
Items ‰ 17 18 (11) 24-25 23 40(4)
HGF Metering Ring Screw Hex Rotor Assy. Spacer Drive Link Special Bolt
08 HGF019007 0213470100 HGF087000 4773010022 0213810406
10 HGF019008 0123480112 HGF107000 4773010034 0213810406
12 HGF019009 0213470125 HGF127000 4773010047 0213810431
16 HGF019010 0213470150 HGF167000 4773010072 0213810456
20 HGF019011 0123470175 HGF207000 4773010097 0213810481

Tools Materials Required for Servicing
HGF Service Manual
HGF service ass'y fixture (See Figure 1)
Clean, petroleum-based solvent
Vise
Pliers
Screw driver
Blunt ended punch
6 pieces of .007 inch (.18 mm) shim stock, approximately
.5 inch (13 mm) wide x 1.5 inch (38 mm) long.
External retaining ring pliers
Tape, plastic electrical
Breaker bar
Sockets: 1/2, 7/8 inch
3/32 inch Allen wrench socket
T-30 Torq socket
Slot type screw driver socket
5/16-24 UNF hex nut (4) required
3/4 inch (19 mm) to 7/8 inch (22 mm) bearing puller
Clean grease
Light weight oil
Torque wrenches: 11–13 in. lb.& 25–35 ft.lb.or Newton Meter
Feeler gauge .003 in. (.08 mm) or .005 in.(.13 mm)
(See disassembly procedure #37)
Electrical continuity checking device
Torque Chart ExplodedView
Part Name Item Number Torque
Socket Head Cap Screws 18 11-13 in-lbs.(1.24-1.47 N m)
Plug and O-Ring Ass'y 6, 7 8-12 ft-lbs. (11-16 N m)
Plug and O-Ring Ass'y 6A, 7A 25-35 ft-lbs.(34-48 N m)
Hex Nut 5/16-24 1 18-22 ft-lbs.(25-30 N m)
Jam Nut 5/8-18 41 25-30 ft-lbs. (34-41 N m)
Jam Nut 13/16-20 UNEF 41 30-40 ft-lbs. (41-55 N m)
8
HGF Series Service Procedure
CONVERSIONS
INCHES mm
0.18
0.375
2.0
3.25
4.0
8.0
4.6
9.5
51.0
82.6
101.6
203.2
Figure 1

9HGF Series Service Procedure
Figure 2
Before you disassemble the HGF Hydraguide unit or any
of its parts, read this entire manual. It provides important
information on parts and procedures you will need to
know to service the HGF.
When disassembling any of the parts, use a clean work
bench. Wash all parts in clean petroleum based solvent
and blow them dry. Keep each part separate to avoid
nicks and burrs.
WARNING: SINCE THEY ARE FLAMMABLE, BE
EXTREMELY CAREFUL WHEN USING ANY SOLVENT.
EVEN A SMALL EXPLOSION OR FIRE COULD CAUSE
INJURY OR DEATH.
WARNING: WEAR EYE PROTECTION AND BE SURE
TO COMPLY WITH OSHA OR OTHER MAXIMUM AIR
PRESSURE REQUIREMENTS.
WARNING: REMOVE STEERING WHEEL WITH A
STEERING WHEEL PULLER AFTER REMOVING
WHEEL NUT. DO NOT LOOSEN WITH HAMMER, AS
THIS COULD DAMAGE UNIT INTERNALLY.
Before you disconnect any hoses, clean off all outside
dirt from around the fittings. Plug the port holes and
hoses immediately after you disconnect the hoses and
before you remove the HGF from the vehicle. This is to
prevent foreign matter from entering the HGF and
damaging it when you clean and reassemble it.
Remove any contact brush cover (49) contact brush
cover seal (48) and related screw and lock washers (50),
and disconnect any horn wire connection to the HGF
unit. Next, remove nuts from the mounting bolts, blow the
unit dry and place it on a work bench.
Components throughout this assembly are stacked on
four bolts and held in alignment with alignment pins
designed to be a slip fit into the components. Use the
minimum force necessary and maximum care to
separate or assemble the components.
The HGF Hydraguide unit has several components that
are of brazed laminate construction, plates and parts
bonded together permanently to form an integral
component that is not subject to disassembly for service.
Disassemble the HGF unit only to the extent shown in
this manual.
CAUTION: Do not force or abuse closely fitted parts,
or you may damage them. Use only genuine Ross or
OEM approved service parts.
The components, required to service an HGF unit and
their service part numbers are available from authorized
OEM parts distributors or other authorized HGF
distributors.
HGF: Disassembly and Inspection
Preparation before disassembly
1. Remove screw and lock washers
(45) and contact brush assemblies
(44) and washers (46) or spacer
(51) from the upper cover and
jacket tube assembly (37) if the
HGF unit is so equipped. See
FIGURE 2.
Remove contact brush
assembly & related
components

10
HGF Series Service Procedure
Figure 6
Figure 5
Figure 4
Figure 3
2. To avoid distorting or
damaging the HGF unit, do
not clamp it directly into a
vise. Clamp a service
assembly fixture described
in FIGURE 1 securely in a
vise, See FIGURE 3, and
place the HGF unit, input
shaft/wheel tube first, into
the service assembly fixture.
Attach the unit to the fixture
with four 5/16-24 UNF nuts.
See FIGURE 4.
Place HGF unit in
service fixture
NOTE: Before beginning the
disassembly of HGF unit, study the
relative positions of the alignment
grooves on the side of the components
in the assembly. Also, note the jacket
tube contact brush cover hole radial
position relative to the side of the unit
with the alignment grooves. The
relative alignment groove positions on
the components and the jacket tube
contact brush cover hole positions
must be maintained at reassembly.
Refer to the alignment groove graphic
on fold-out.
NOTE
3. Loosen plug (6) or hex plug
(6A) assembly in the port
cover (2) for disassembly
after the port cover is
removed from the unit. Use
an appropriate type
screwdriver, T-30 Torx driver
or 7/8 inch hex socket. See
FIGURE 5.
Loosen plug assembly
4. Remove the four retaining
nuts (1) from the port cover
(2) assembly. Be careful not
to damage the protruding
ports. See FIGURE 6.
Replace any nut that has
damaged threads or hex.
Remove port cover nuts

11 HGF Series Service Procedure
Figure 8A
Figure 9
Figure 8
Figure 7
NOTE: The unit has two different
length spring sets. The set you have
just removed from the port manifold
are three-quarter inch (19 mm) long.
Keep this set of three springs
separate from the next set of three
springs to be removed.
10. Inspect the springs for bent or
distorted coils. If a spring is
broken or deformed, all six springs
in the unit should be replaced.
5. Grasp the port cover (2)
assembly and lift it from the
unit. Discard three, four, or
five seal rings (4) and seal ring
(3) or if included white seal
ring (3A). See FIGURE 7.
Remove loose check ball (52)
from top of port manifold (8) if
included.
Remove port cover
6. If included, remove the
loosened plug (6) and o-ring
(7) assembly from the port
cover. Be ready to catch the
steel check ball (5) as it falls
from its cavity. Discard o-ring
(7). See FIGURE 8.
Remove plug
6A. If included, removed the
loosened hex plug (6A) and o-
ring (7A) from the port cover
(2). Discard o-ring. Remove
relief valve cartridge (5A) and
spring (5B) assembly. A bent
or lost spring (5B) can be
serviced separately. See
FIGURE 8A. Do not try to
disassemble relief valve
cartridge (5A).
Remove hex cap &
relief valve cartridge &
spring assy.
Inspect port cover 7. Inspect the port cover (2) for
port fitting sealing surface
scratches and thread damage.
Replace port cover, if these
conditions are evident.
NOTE
8. Carefully lift the port manifold
(8) (3 plates bonded together)
from the unit. See FIGURE 9.
Remove springs
NOTE: Be prepared to catch
three springs (9) which may
become disengaged when
removing the port manifold.
NOTE
Remove port manifold
9. Remove three springs (9) from
the port manifold (8).
Inspect springs

12
HGF Series Service Procedure
Figure 13
Figure 12
Figure 11
Figure 10
11. Inspect the ground surfaces of
the port manifold (8). You
should notice a "normal"
polished pattern due to the
rotation of the valve plate (13)
and hex drive assembly (10).
All edges should be sharp and
free of nicks and burrs. The
surfaces of the port manifold
should be free of scratches or
scoring. If any of these wear
conditions exist, replace the
port manifold.
Inspect port
manifold
CAUTION: Many components
in the unit have finely ground
surfaces. Be careful not to
nick or scratch these surfaces.
CAUTION
12. Remove the valve ring (12),
discard the two seal rings (3).
See FIGURES 10 and 11. The
valve ring should be free of
nicks and scoring.
Remove valve ring
13. Remove the valve plate (13) by
lifting it from the isolation
manifold (15).
Remove valve plate
14. Inspect the slot edges and
ground surfaces. If the valve
plate (13) shows nicks or
scoring or the edges are not
sharp, it must be replaced.
See FIGURE 12.
Inspect valve plate
NOTE: The valve ring (12)
and valve plate (13) are a
matched set and must be
replaced as a set.
NOTE
15. Remove three springs (14)
from the isolation manifold (15)
pockets. See FIGURE 13.
Remove springs
NOTE: The unit has two
different length spring sets.
The set you have just removed
from the isolation manifold is
one-half inch (13 mm) long.
Keep this spring set separate
from the set removed from the
port manifold (8).
NOTE

13 HGF Series Service Procedure
Figure 17
Figure 16
Figure 15
Figure 14
16. Inspect the springs (14), for
bent or distorted coils. If a
spring is broken or deformed,
all six springs in the unit must
be replaced. See FIGURE 14.
Inspect springs
17. Remove hex drive assembly
(10) from drive link (16). See
FIGURE 15.
Remove hex drive
assembly
18. The pin in the hex drive
assembly (10) should not show
wear and must be firmly
pressed in place. The sides of
the hex and the slot should
not have grooves or scoring. If
the hex drive assembly (10)
shows signs of this type of
wear, it must be replaced.
Inspect hex drive
assembly
19. Remove the two alignment
pins (11) that align the port
manifold (8), valve ring (12)
and isolation manifold (15).
See FIGURE 16.
Remove alignment pins
NOTE: A service kit of nine
alignment pins (11) is available for
servicing the unit.
NOTE
20. Remove the isolation manifold
(15), (four plates bonded together).
See FIGURE 17.
Remove isolation
manifold