Information Bulletin

2.0 Seized Water Pump Troubleshooting

Date: June 20, 2024
Bulletin Name: FDM-IB-004
Model: Oshkosh S-Series 2.0
Units Affected: Front Discharge Mixers

Purpose:

This bulletin provides instructions for checking specific areas of the water pump assembly that may lead to a
seized water pump condition. Potential causes of a seized water pump include shaft tubes sitting unevenly, tie
rods torqued unevenly, roller bearings incorrectly positioned on driveshaft, and motor shaft too tight.

Notice:

• Read and understand bulletin 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

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

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

SAFETY NOTICE

All hydraulic pressure 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.

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

WARNING

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

Tools and Equipment Required:
Customer to supply:
• Hand tools
• Torque wrench (inch and foot pounds)
• Deburring tool
• 2 - 3" piece of metal pipe - 1.25" OD/1" ID

1

Procedure:

Lockout/Tagout

1. Park vehicle on a flat level 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

Driveshaft Tubes Sitting Unevenly

3. Loosen and remove screws securing water pump motor to upper bearing carrier. See Figure 1. Set and
secure motor to side.
Screws

Upper Bearing
Carrier

Figure 1 - Water Pump Motor

2

4. Loosen clamp securing output hose to 90° elbow and disconnect hose from elbow. See Figure 2.
5. Loosen and remove screws and lock washers securing water pump assembly to water tank. See Figure 2.
Save screws and lock washers for reinstallation.
90° Elbow

Clamp

Output Hose

Figure 2 - Output Hose

6. Remove water pump assembly from water tank.
7. Loosen and remove tension clamp from lower hose connection. See Figure 3.
8. Disconnect hose from lower 90° fitting. See Figure 3.

Hose

Tension Clamp

90° Fitting

Figure 3 - Water Pump Assembly

9. Loosen and remove the four screws securing lower volute housing to the upper volute housing. See Figure 4.
Save screws for reinstallation.
Upper Volute Housing
Screws

Figure 4 - Water Pump Assembly

3

10.

Remove the lower volute housing from upper volute housing. See Figure 5.

Upper Volute Housing

Lower Volute Housing

Figure 5 - Volute Housing

11.
Make sure impeller is not rubbing on the upper volute housing and there is a clear gap. See Figure 6. If
there is no gap proceed with Steps 12 and 13 then perform Steps 35-44 to adjust the roller bearings. If there is a
clear gap proceed with Steps 12 - 32.

Gap
Upper Volute Housing

Impeller

Figure 6 - Impeller Gap

12.

Loosen and remove the impeller nut. See Figure 7. Save nut for reinstallation.

13.
Remove impeller, key, and flat washer from driveshaft. See Figure 7. Save impeller, key, and flat washer
for reinstallation.

Flat Washer

Impeller

Nut
Key

Figure 7 - Impeller Removal

4

14.
Loosen and remove the four nuts securing the upper volute housing to the tie rods. See Figure 8. Save
nuts for reinstallation.
15.

Remove upper volute housing from driveshaft. See Figure 8. Save upper volute housing for reinstallation.
Driveshaft

Upper Volute Housing

Tie Rods

Nuts

Figure 8 - Upper Volute Removal

16.

Remove the lower extruded tube from driveshaft. See Figure 9. Save tube for reinstallation.

17.

Remove the middle bearing carrier from driveshaft. See Figure 9. Save bearing carrier for reinstallation.

18.

Remove the upper extruded tube from driveshaft. See Figure 9. Save tube for reinstallation.
Upper Extruded Tube

Middle Bearing
Carrier
Lower Extruded Tube

Figure 9 - Extruded Tube Removal

19.
Chamfer inside edge of each end of the upper and lower extruded tubes using a deburring tool. Tube
ends only need a small chamfer. See Figure 10. Thoroughly clean ends of extruded tubes after chamfering.
Chamfer Inner Edge

Figure 10 - Tube Chamfer

5

20.

Reinstall upper extruded tube over driveshaft. See Figure 11.

21.

Reinstall middle bearing carrier over driveshaft and tie rods. See Figure 11.

22.

Reinstall lower extruded tube over driveshaft. See Figure 11.

23.

Install upper volute housing on driveshaft and tie rods. See Figure 11.

24.
Reinstall nuts on end of tie rods. Final tighten nuts using a two-step torque process in a star pattern. The
first torque step is 55 in. lbs., and the second and final torque is 110 in. lbs. See Figure 11.
• Make sure the driveshaft can be rotated as the nuts are torqued.
• If driveshaft binds after torquing a nut, back nut(s) off and retorque until driveshaft spins freely by hand.
Upper Extruded Tube

Middle Bearing
Carrier

Upper Volute Housing
Lower Extruded Tube

Tie Rod
Driveshaft

1
4

Nuts

3
2
Torque Sequence

Figure 11 - Assembly

25.
Reinstall flat washer, key, impeller and nut on driveshaft. Final tighten impeller nut to 17 ft. lbs. See
Figure 12.

Flat Washer

Impeller

Nut
Key

Figure 12 - Impeller Installation

6

26.
Reinstall lower volute housing over impeller. Secure lower volute housing to upper volute housing with
four screws removed in Step 9. Final tighten screws to 17 ft. lbs. using a star pattern.
• Make sure the driveshaft can be rotated as the screws are torqued.
• If driveshaft binds after torquing a screw, back screw(s) off and retorque until driveshaft spins freely by
hand.

1

Screws

4

3
2

Upper Volute Housing
Impeller

Lower Volute Housing
Figure 13 - Assembly

Torque Sequence

27.
Reconnect hose disconnected in Step 8 to lower volute housing 90° fitting. Secure hose to fitting with
spring clamp.
28.

Reinstall water pump assembly in water tank. See Figure 14.

29.
Apply Loctite® 242 to screws removed in Step 5 and install screws with lock washers to secure water
pump assembly to water tank. See Figure 14. Final tighten screws to 17 ft. lbs.
30.

Reconnect output hose to 90° elbow and secure with hose clamp.

31.

Reinstall motor on upper bearing carrier. Install screws removed in Step 3 and final tighten to 17 ft. lbs.
Screws

Upper Bearing
Carrier

Hose Clamp

Output Hose
Screws and Lock Washers

Figure 14 - Water Pump Motor

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32.
Remove lockout/tagout and check operation of water pump. If water pump operates correctly process is
complete. If water pump does not operate correctly continue to Step 33.
33.

Reapply lockout/tagout to vehicle and repeat Steps 3 - 6 to remove water pump from tank.

Roller Bearings Incorrectly Positioned on Driveshaft

34.
Check gap between the lower bearing housing and adapter plate. See Figure 15. If the gap is correct go
to Step 47. If the gap is incorrect go to Step 35.

Gap Too Large

Correct Gap

Figure 15 - Water Pump

35.
Loosen and remove screws securing bearing carriers to adapter plate. See Figure 16. Save screws for
reinstallation.
Bearing Carriers

Adapter Plate

Screws

Figure 16 - Bearing Carrier Removal

36.

Remove bearing carriers and driveshaft from pump assembly. See Figure 17.
Driveshaft

Bearing Carriers

Figure 17 - Bearing Carrier Removal

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37.

Remove upper bearing carrier from lower bearing carrier. See Figure 18.

Upper Bearing
Carrier

Lower Bearing
Carrier
Driveshaft

Figure 18 - Bearing Carriers

38.

Place the lower bearing carrier and driveshaft vertically on a table or workbench. See Figure 19.

39.
Find an adjustable wrench and piece of metal pipe that fits on the driveshaft. See Figure 19. The piece of
metal pipe should not be a larger diameter than the bearing carrier bearing.
40.
Using a hammer tap the adjustable wrench end to move the bearing placement. See Figure 19. The
bearing will not need much adjustment if the gap identified is small.

Hammer

Driveshaft

Adjustable
Wrench

Metal Pipe
Bearing

Figure 19 - Bearing Adjustment

9

41.

Remove adjustable wrench and metal pipe from driveshaft and set aside.

42.

Reinstall driveshaft and lower bearing carrier in water pump assembly. See Figure 20.

43.
Check to make sure step in driveshaft protrudes past the base surface of the upper volute housing plate.
See Figure 20. If step in driveshaft does not protrude far enough repeat Steps 38- 43.

Driveshaft

Upper Volute
Housing Plate

Correct

Incorrect

Figure 20 - Driveshaft End

44.
Reinstall upper bearing carrier on lower bearing carrier with 3 screws removed in Step 35. Final tighten
screws to 110 in. lbs.
Lower Bearing
Carrier
Upper Bearing
Carrier
Screws

Figure 21 - Bearing Carrier Installation

45.

Perform Steps 25-30 to assemble lower portion of water pump assembly.

46.
Remove lockout/tagout and check operation of water pump. If water pump operates correctly process is
complete. If water pump does not operate correctly continue to Step 47.

10

47.

Reapply lockout/tagout to vehicle.

Motor Shaft is too Tight

48.
Loosen and remove hydraulic hoses connected to pump motor. See Figure 22. Cap or cover hose ends to
prevent hydraulic system contamination.
49.
Loosen and remove screws securing water pump motor to upper bearing carrier. See Figure 22. Save
screws for reinstallation.
Screws

Upper Bearing Carrier

Hydraulic Hoses

Figure 22 - Water Pump Motor

50.

Secure motor in a bench clamp.

51.

Remove coupling spider from motor. See Figure 23.

Coupling Spider

Figure 23 - Water Pump Motor

52.
Place a screwdriver or small crowbar in between coupling teeth and spin the motor shaft with screwdriver
or crowbar. See 24.
53.
Spin motor shaft in both the clockwise and counter clockwise for 1-2 minutes by hand. Repeat the
process 2-3 times for both directions.

Figure 24 - Water Pump Motor

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54.

Reinstall coupling spider removed in Step 51.

55.

Install motor on upper bearing carrier. See Figure 25.

56.

Secure motor to upper bearing carrier with screws removed in Step 49. Final tighten screws to 17 ft. lbs.

57.

Install hydraulic hoses disconnected in Step 48. See Figure 25.

Hydraulic Hose
#3704
(45 ft. lbs.)

Screws

Hydraulic Hose
#3702
(12 ft. lbs.)

Upper Bearing Carrier

Figure 25 - Water Pump Motor

58.
Remove lockout/tagout and check operation of water pump using the front fender remote control. If
coupler hub doesn't turn let system run for 5-10 seconds, turn system off, then back on. Repeat this process
3 - 4 times.
59.
If water pump is still not operational after performing all previous steps, contact service representative for
additional support.
60.

Remove wheel chocks.

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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