Technical Service Information Bulletin
Date: September 8, 2020
Bulletin Name: FDM-TSIB-014
Model: Oshkosh S-Series
Units Affected: SN 800613 - 808355

2.0 Hydraulic System

Purpose:
This bulletin provides instruction and information on required vehicle hydraulic system updates that address
performance deficiencies in the vehicle’s hydraulic system.
The hydraulic water pump return hose needs to be rerouted directly to the hydraulic reservoir to eliminate the
possibility of motor seal failure during different hydraulic load scenarios.
The mixer motor drain hose needs to be rerouted to prevent oil overheating.
Failure to complete these required system updates could lead to component failure.

Notice:
• This bulletin should be read and understood in its entirety before performing this procedure.
• All procedures outlined in the bulletin must be performed by skilled service personnel. Refer to the product
service manual for descriptions of maintenance procedures.

WARNING

WARNING

All hydraulic pressures must be relieved from
the hydraulic system prior to removing any
components from the system to prevent oil
from spraying or functions and systems
from failing.

Hydraulic systems are hot. DO NOT TOUCH!
Serious personal injury may result from hot
oil. When you have completed working on the
hydraulic systems, thoroughly clean any
spilled oil from the equipment. Do not spill
any hydraulic fluids on the ground. Clean any
hydraulic fluids from your skin as soon as
you have completed your maintenance and
repairs. Dispose of used oil and filters as
required by law.

SAFETY NOTICE

Perform your company’s Lockout/Tagout
procedure. If your company does not have a
Lockout/Tagout procedure, follow OSHA
1910.147 and 1910.146 Confined Space as
appropriate.

WARNING

Hydraulic systems operate under high
pressure—only experienced persons should
attempt repairs or troubleshooting on
hydraulic systems.

SAFETY NOTICE

Use appropriate Personal Protective
Equipment (PPE) as required by your
company.

WARNING

Never remove hydraulic pipes/tubing, fittings,
and adapters until all pressure has been
relieved from the hydraulic system.

1

Tools and Equipment Required:
Customer to supply:
• Torque wrench (foot pounds)
• Hand Tools
• O-ring Lube

Parts Required:
Item

Part Number

1

A000T437

2

1260521

3

Description

Qty.

HOSE ASSY #12 CR 126.0 (3806)

1

FTG,90 12JIC-12ORG MM ST

1

A000C244

CLIP,CSHN 1.13IN ST VY

2

4

A000E788

SADDLE MOUNT,DUAL SWIVEL

1

5

A000C235

CLIP,CSHN .81IN ST VY

4

6

1260627

FTG,PLUG 6ORG M ST EXHEX

1

7

1144772

FTG,ST 8JIC-8ORG MM ST

1

8

A000T589

HOSE ASSY #8 CR 175.0 (3704)

1

9

1131569

FTG,ST 12JIC-8JIC MM ST

1

10

1243674

SCR,FLG,HEX .38-16X1.25 G8 MB

1

11

0120200

NUT,FLG,LKDT, .38-16 G8 MB

1

12

A000C018

CABLE TIE 6.30X.200

8

Procedure:
Lockout/Tagout
1. Place unit on a flat surface, block truck tires, and perform your company’s Lockout/Tagout procedure. If your
company does not have a Lockout/Tagout procedure, follow OSHA 1910.147 and 1910.146 Confined Space as
appropriate.
2. The vehicle’s BATTERY DISCONNECT switch is located on the left-hand side of the battery box. Use the
battery disconnect switch when performing any maintenance so the vehicle cannot accidentally be started.
a. Turn the battery disconnect switch (Figure A, Item 1) counterclockwise so the hole on the switch aligns
with the hole in the bracket (Figure A, Item 2).
b. Install the safety lockout device ring (Figure B, Item 1) through the holes on the battery disconnect switch
and the bracket.
c. Install a padlock (Figure B, Item 2) onto the safety lockout device ring, lock it, and put the key in your
pocket. If more than one person is working on the vehicle, each person must install his or her own padlock.

1

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1

2

2

Figure A

Figure B

2

Hydraulic System Cleanliness
Today’s high system pressures and speeds make clean systems mandatory. A common source of trouble in a
system is dirt. Dirt may enter at any time from receipt of the components, to new vehicle delivery or its repair.
Scheduled maintenance and good assembly practices will result in prolonged service life of the hydraulic
components.
The following practices have been, and always will be, good, sound manufacturing, preventative maintenance,
and servicing procedures. They are not costly to institute, but can be highly beneficial to the vehicle user.
Good Housekeeping.
The most obvious and essential point in stressing cleanliness is good housekeeping. Regularly scheduled
cleaning, sweeping and washing of assembly and service areas reduce the presence of environmental
contamination.
As part of the good housekeeping practices, the location of the service area is very important. This area should
be separated from welding, sanding and painting operations. It should also be relatively clear of any outside
doors which may be open allowing dust to be blown into the service area.
All hydraulic components should be stored in a clean dry place. Units and components should not be unpacked
unless there is an immediate need for them. Stock should be rotated regularly so that the oldest units are used
first. The units must be stored with ports plugged. Port protection such as plastic plugs or shipping plugs should
not be removed until circuit components are ready for installation.
Fittings and Hoses.
Fittings and hoses which have not been equipped with shipping caps, or have been removed for rework of
hydraulic components, must be thoroughly cleaned. Flush fittings or hoses with mineral spirits and air dry. Check
forged steel or cast fittings for burrs, foundry sand or casting finns. Failure to remove defects of this nature could
result in an early malfunction or component failure. All welded or silver brazed piping should be pickled. It should
be neutralized, dried, and oiled with a preservative to prevent rusting. Openings should then be sealed until
use at assembly. Mobile Bulletin M-1221-S which covers ”Preparation of Pipes, Tubes and Fittings” should be
referred to.
Reservoir.
In the operation of hydraulic systems, the reservoir is one of the greatest sources of contamination.
Reservoir Filling. Exercise care to maintain cleanliness when filling the hydraulic system. It is suggested to
pump the hydraulic fluid through a 10 micron filter to prevent contamination from entering the system. Vickers
OFM series filters are excellent for this type of duty. In addition, the nozzle of the filling hose should be wiped
clean with a lint-free paper towel or cloth prior to use.

3

Hydraulic Water Pump Return Hose Reroute
3. Disconnect the hydraulic water pump motor return hose and remove the existing outlet fitting, see Figure 1.

Motor
Motor Supply Line
Motor Return Line

Figure 1 - Hydraulic Water Pump Motor

4. Remove the mounting screws securing the hydraulic motor to the pump assembly, see Figure 2.
5. Remove the hydraulic motor from the pump assembly and set aside.

Motor

Mounting Screws

Figure 2 - Hydraulic Water Pump Motor Removal

4

6. Disconnect the hydraulic motor return hose and fitting from the manifold, see Figure 3. Return hose and
fitting will not be reused.
7. Apply O-ring lube to plug (1420427) and install in manifold where return hose was removed, see Figure 3.
Torque plug to 21 ft. lbs.

Manifold
Return Hose

Figure 3 - Hydraulic Water Pump Motor Return Hose

8. Remove the three Allen screws securing the motor upper spacer to the pump tank plate, see Figure 4.
9. Rotate upper spacer 120° clockwise and reinstall the three Allen screws. Torque Allen screws to 15 ft. lbs.

Allen Screws
Upper Spacer
Tank Plate

Figure 4 - Pump Assembly Motor Spacer

5

10.
Install the motor, orientate the motor with the outlet port facing the rear as shown in Figure 5. Final tighten
mounting screws to 15 ft. lbs.

Mounting
Screws

Motor

Figure 5 - Hydraulic Water Pump Motor Installation

11.

Apply O-ring lube to new fitting (1144772) and install in the motor outlet. Torque fitting to 36 ft. lbs.

12.
Loosen the existing motor supply hose and orientate hose’s 90° fitting to the 4 o’clock position. Torque
inlet hose fitting to 12 ft. lbs.
13.
Install the 8JIC side of union (1131568) into the end of the new water pump return hose (A000T589).
Final tighten to 45 ft. lbs.

6

NOTE

Keep the end of the hose disconnected from
the mixer motor above the level of the
hydraulic reservoir to prevent draining oil
from the hydraulic reservoir.
14.
Disconnect the two P-clips securing the motor case drain hose then disconnect the mixer motor case
drain hose from the mixer motor, see Figure 6.

Mixer Motor
Drain Hose

P-Clip

Figure 6 - Mixer Motor Hose

7

15.
Secure the end of the mixer motor drain hose to the 12JIC side of the union installed in the end of the
new water pump return hose (A000T589). Final tighten to 84 ft. lbs.

NOTE

Leave the 45 end of the new water pump
return hose plugged until the hose is routed
to the water pump motor.
°

16.
Route the new water pump motor return hose assembly through the rear pedestal cross member and long
the right-hand frame rail, see Figure 7

Rear Pedestal

Union
Rear Pedestal
Crossmember

Figure 7 - Return Hose Routing

8

17.
Loosely route return hose underneath and behind air tanks and along the right-hand frame rail stainless
steel tubes, see Figure 8.
18.
Remove cap from the end of hose (A000T589) and connect to the motor outlet fitting. Orientate hose’s 45°
fitting to the 5 o’clock position. See Figure 8. Torque outlet hose fitting to 35 ft. lbs.

NOTE

New P-clip mounting hardware is only
required on 2303 and 2104 model trucks.
Verify mounting location of P-clip on the
transfer case crossmember to see if
mounting hardware already exists in the
location.
19.
Secure hose to transfer case crossmember using P-clip (A000C235), 3/8-16 x 1.25 inch bolt (A000A532)
and nut (A000A690). Do not final tighten P-clip mounting hardware at this time.

P-Clip

Mounting
Hardware

Motor Return Hose

Transfer Case
Crossmember
Figure 8 - Hydraulic Water Pump Return Hose Installation

9

20.
Secure return hose to the three existing Stauff clamps using P-clips (A000C235). Use the Stauff clamp
hardware to secure the P-clips. Do not final tighten mounting hardware at this time.
21.
Secure return hose to stainless hard lines with cable ties at three locations shown in Figure 9. Do not final
tighten cable ties at this time.

P-Clip

Stauff Clamp

Cable Tie

Figure 9 - Water Pump Motor Return Hose Installation

10

22.
Secure the return hose behind the rear pedestal crossmember with P-clip (A000C244) to Stauff clamp.
Use the Stauff clamp hardware to secure the P-clip. Do not final tighten mounting hardware at this time. See
Figure 10.
23.

Secure the reservoir side of the hose with cable ties, see Figure 10.

P-Clip

Cable Tie

Cable Tie

Figure 10 - Water Pump Motor Return Hose Installation

24.
Verify the hose from the water pump outlet to the hydraulic reservoir is routed correctly and evenly spaced
to avoid slack. With hose correctly routed final tighten the cable ties, Stauff clamp hardware (9 ft lbs.), and
transfer case P-clip mounting hardware (35 ft. lbs.).

11

Mixer Motor Hose Reroute
25.
Install the end of new hose (A000T437) to the open 90° fitting on the mixer motor case drain port,see
Figure 11. Final tighten to 84 ft. lbs.

Mixer Motor Drain Hose

Mixer Motor

Figure 11 - Mixer Motor Hose

26.
Route the mixer motor drain hose to the mixer pump along the right-hand frame rail and through the
center opening of the cooling tower base, see Figure 12. Install P-clips removed earlier and install additional
P-clip (A000C244) to secure hose at locations shown in Figure 12. Final tighten P-clip mounting hardware to 35
ft. lbs.

Clamp
Mixer Motor

Mixer Motor Drain Hose
Figure 12 - Mixer Motor Drain Hose - Mixer Motor Connection

12

27.
Apply O-ring lube to 90° fitting (1260521) and install in front left mixer pump port, see Figure 13. Final
tighten to 142 ft. lbs.
28.

Connect the mixer motor drain hose to the 90° fitting, see Figure 13. Final tighten connection to 84 ft. lbs.

Mixer Pump
90° Fitting

Mixer Motor
Drain Hose
Figure 13 - Mixer Motor Drain Hose - Mixer Pump Connection

29.
Secure the mixer motor drain hose to the hydraulic reservoir filter suction line using two cable ties and
saddle mount (A000E788), see Figure 14.

Cable Ties
Saddle Mount

Hydraulic Filter
Suction Hose

Mixer Motor
Drain Hose

Figure 14 - Mixer Motor Drain Hose

13

Filling the Hydraulic Reservoir
30.

Clean the area around the hydraulic reservoir fill cap, see Figure 15.

31.

Remove the fill cap and fill the reservoir with new approved fluid until the level is to the MAX mark.

32.

Reinstall the reservoir fill cap.

MAX Level

Fill Cap

MIN Level

Figure 15 - Hydraulic Reservoir Fill

33.

Remove lockout/tag.

Software Update
A vehicle software update is required after completion of the procedure for increased cooling, better fan operation,
and enhanced chute functionality.

Continuous Improvement:

The change included in this document is part of the
McNeilus Continuous Improvement Process.
McNeilus’s quality policy is providing customer satisfaction
through innovative products, dedicated service, and a
constant focus on continuous improvement.
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