S-1671 Service Bulletin/Repair Instructions

HYDRAULIC LIMIT STOP VALVE FOR KNORR-BREMSE® IPS90™ AND IPS100™

(INTEGRAL POWER STEERING) HYDRAULIC POWER STEERING GEARS FOR

COMMERCIAL VEHICLES
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND

FOLLOW THESE INSTRUCTIONS

TO AVOID PERSONAL INJURY OR DEATH:
Figure 1 - Hydraulic Limit Stop Valve
Steering gears are heavy. When assembling and

disassembling the steering gears, make sure to follow

all safety protocols.

Steering fluid can get hot and reach temperatures up to

250° F (121° C). Use the appropriate PPE when servicing.

Comply with OSHA guidelines.

Avoid high-pressure hydraulic wash on steering gears

and steering sub-systems.

Unless and/or otherwise mentioned, use of hammer

or heat to disassemble steering components is not

permitted.

Use manufacturer-recommended steering fluid only.

Mixing of fluids may cause internal damage to rubber

or plastic components.
When working on or around a vehicle, the following

guidelines should be observed AT ALL TIMES:

▲Park the vehicle on a level surface, apply the parking

brakes, and always block the wheels. Always wear personal

protection equipment.

▲Stop the engine and remove the ignition key when working

under or around the vehicle. When working in the engine

compartment, the engine should be shut oﬀ and the ignition

key should be removed. Where circumstances require that

the engine be in operation, EXTREME CAUTION should be

used to prevent personal injury resulting from contact with

moving, rotating, leaking, heated, or electrically charged

components.

▲Do not attempt to install, remove, disassemble, or

assemble a component until you have read, and thoroughly

understand, the recommended procedures. Use only the

proper tools and observe all precautions pertaining to use

of those tools.

▲If the work is being performed on the vehicle’s air brake

system, or any auxiliary pressurized air systems, make

certain to drain the air pressure from all reservoirs before

beginning ANY work on the vehicle. If the vehicle is

equipped with a Bendix® AD-IS® air dryer system, a Bendix®

DRM™ dryer reservoir module, a Bendix ® AD-9si ®, AD-HF®,

or AD-HFi™ air dryer, be sure to drain the purge reservoir.

▲Following the vehicle manufacturer’s recommended

procedures, deactivate the electrical system in a manner

that safely removes all electrical power from the vehicle.

▲Never exceed manufacturer’s recommended pressures.

▲Never connect or disconnect a hose or line containing

pressure; it may whip and/or cause hazardous airborne

dust and dirt particles. Wear eye protection. Slowly open

connections with care, and verify that no pressure is

present. Never remove a component or plug unless you are

certain all system pressure has been depleted.

▲Use only genuine Bendix ® brand replacement parts,

components, and kits. Replacement hardware, tubing, hose,

ﬁttings, wiring, etc. must be of equivalent size, type, and

strength as original equipment and be designed speciﬁcally

for such applications and systems.

▲Components with stripped threads or damaged parts should

be replaced rather than repaired. Do not attempt repairs

requiring machining or welding unless speciﬁcally stated

and approved by the vehicle and component manufacturer.

▲Prior to returning the vehicle to service, make certain all

components and systems are restored to their proper

operating condition.

▲For vehicles with Automatic Traction Control (ATC), the ATC

function must be disabled (ATC indicator lamp should be

ON) prior to performing any vehicle maintenance where

one or more wheels on a drive axle are lifted oﬀ the ground

and moving.

▲The power MUST be temporarily disconnected from the

radar sensor whenever any tests USING A DYNAMOMETER

are conducted on a vehicle equipped with a Bendix ®

Wingman ® system.

▲You should consult the vehicle manufacturer's operating

and service manuals, and any related literature, in

conjunction with the guidelines above.
1
KIT COMPONENTS

The hydraulic limit stop valve service kit for Knorr-Bremse®

IPS90™ and IPS100™ (Integral Power Steering) hydraulic

power steering gears contains the following parts:

Item No.
Description
Qty.
150
Stop Valve Assembly
1
942
Plunger Assembly
1
946
Plug
1
947
O-ring
1
REQUIRED TOOLS

•
Drain Pan
•
M24 Socket with Ratchet
•
Socket (with 14-mm key range) and Ratchet
•
Tweezers
The hydraulic limit stop valves in steering gears are used

to reduce the pressure build-up during the end of travel in

the steering gear. By decreasing the pressure build-up, the

hydraulic limit stop valves help to reduce system temperature

and overloading other steering components. There are two

hydraulic limit stop valves in a steering gear: one on the valve

housing and the other on the main housing. See Figure 2.

The hydraulic limit stop valves adjust automatically based

on the wheel cut required in left and right turns.

LOCATION 1
(947) O-ring
LOCATION 2

(150) Hydraulic Limit Stop

Valve Assembly
(942) Plunger Assembly
(156) O-ring

(157) O-ring

Location 1
Location 2
Figure 2 - Hydraulic Limit Stop Valve - Locations

2
The hydraulic limit stop valve must be replaced in either of

the following instances:

•
When there is an external oil leak from the hydraulic

limit stop valve; or
•
When the wheel cut is reduced.
The hydraulic limit stop valve must be reset in either of the

following instances:
AUTOMATIC HYDRAULIC LIMIT STOP VALVE

SERVICE PROCEDURE
(946) Plug
Once the plunger in the hydraulic limit stop valve is

pressed in, it cannot be repaired and reused in the

steering gear.
•
When the pitman arm is mistimed; or
•
When wheel cut is increased.
Improper assembly of hydraulic limit stop valves can

lead to damage in the steering system.

NOTE: The initial hydraulic limit stop valve setting should

be done on new gears or on manufacturers' aftermarket

gears. If the hydraulic limit stop valves on a used gear are

replaced with new sets, the hydraulic limit stop valve setting

procedure must be followed.
The axle stops and all steering linkage must be set

according to the vehicle manufacturer's specification.

The pitman arm timing mark should align with sector

shaft (output shaft) timing mark for the hydraulic limit

stop valves to be set correctly.
1. E

 ngage the parking brake. Jack up the vehicle at the

front axle. Ensure the tires are not touching the ground.

2. W

 ith the engine off and the vehicle unloaded, slowly

turn the steering wheel from the center position to full

turn in either the left or right direction until the axle stop

contact is made. Pull hard on the steering wheel after

the axle stop is in contact.

3. A

 fter the axle contact is made, return the steering wheel

to center and then turn the steering wheel in the other

direction until the axle contact is made. Pull hard on the

steering wheel after the axle stop is in contact.

4. L

 ower the jack. The front axle is now loaded. Turn the

steering wheel from left to right until the axle contact is

made during both turns. Make sure the chassis is not

flexing when the axle stops contact.
NOTE: Do not turn the output shaft more than ±30 degrees

from the center position until the pitman arm and drag-link

are connected.
REPLACEMENT OF THE HYDRAULIC LIMIT

STOP VALVE IN LOCATION 2

See Figure 2.
ATTENTION

In case an already assembled hydraulic limit stop valve

assembly (150) is part of the service kit, the following

steps to disassemble and assemble the o-rings on the

cartridge in location 2 can be skipped.

1. Place a drain pan under the steering gear.
Hydraulic limit stop valves should not be disassembled

while the engine is running. Do not turn the steering

wheel with the hydraulic limit stop valves disassembled.

Ensure the vehicle tires are straight ahead while

replacing the hydraulic limit stop valves.
There is no need to disassemble the hydraulic limit stop

valve if the steering gear needs hydraulic limit stop valve

adjustments. Never reuse the hydraulic limit stop valve

after removing it from the steering gear.
REPLACEMENT OF THE HYDRAULIC LIMIT

STOP VALVE IN LOCATION 1

See Figure 2.
2. U

 sing an M24 socket, un-torque the hydraulic limit stop

valve assembly from the steering gear.

NOTE: If the threads on the housing are damaged, assembly

of the hydraulic limit stop valve is not possible.

3. A

 ssemble the o-rings to the new hydraulic limit stop

valve assembly, starting with o-ring (157) followed by

o-ring (156).

NOTE: Ensure the o-ring and o-ring surface are clean.

4. U

 nmask the threads on the housing. Clean the masked

area.

5. U

 sing an M24 socket, torque the hydraulic limit stop

valve assembly to 73.6 N•m – 83.4 N•m.
1. Put a drain pan below the hydraulic limit stop valve.

2. R

 emove the plug (946) together with the o-ring (947) by

using a ratchet with a 14-mm key range socket.

3. Use tweezers to remove the spring.

4. Use tweezers to remove the plunger assembly (942).

5. Install the new plunger assembly (942).

6. Install the spring.

7. Carefully put the new o-ring (947) on the new plug (946).

8. Tighten the plug (946) to 23 N•m – 27 N•m.
3
SINGLE GEAR BLEEDING PROCEDURE

REQUIRED TOOLS

•
Hex 8 Wrench
•
Drain Pan
If the gear is mounted with the bulge in the housing for the

sector shaft hanging below the piston cylinder, shown in

Figure 3, perform the following procedure:

1. W

 ith the weight of the vehicle on the ground, start the

engine and let it run at idle speed.
Figure 4 - Single Gear Bleeding Procedure - Shaft Above

Piston Cylinder
2. T

 urn the steering wheel back and forth from full lock to

full lock three (3) times. Hold pressure on the steering

wheel for about five (5) seconds when you reach the

end of travel in each direction.
For the following steps, identify if a left- or right-hand truck

gear is installed.
3. C

 enter the steering wheel. The bleeding procedure is

complete.
A. W

 ith assistance, turn the steering wheel all the way to

the left. Open the bleeder plug one half turn to one (1)

turn using a Hex 8 wrench. With the bleeder still open,

turn the wheels all the way to the right. Confirm the air

bubbles drain through the tube. When you get all the

way to the right, shut the bleeder and torque it to 6.9

N•m – 12.7 N•m. Turn the wheels all the way back to the

left and repeat the procedure four (4) or more times until

no air bubble can be seen through the tube.
Figure 3 - Single Gear Bleeding Procedure - Shaft Below

Piston Cylinder

If the gear is mounted with the bulge in the housing for

the sector shaft sitting above the piston cylinder, shown in

Figure 4, perform the following procedure:

1. L

 ocate the bleeder plug on the steering gear sector

shaft housing.

2. M

 any newer model gears do not have the bleeder plug,

even if they are mounted in this manner. Instead, there

is a bleed passage cast into the housing which allows

the air to be carried to the bearing cap. Bleed this type

of gear using steps 1 and 2 for gears mounted with the

bulge in the housing for the sector shaft hanging below

the piston cylinder.

3. W

 ith the weight of the vehicle on the ground, start the

engine and let it run at idle speed.
Left-Hand Truck Gears
NOTE: THE BLEEDER SHOULD ONLY BE OPEN AS YOU

ARE TURNING RIGHT! If it is open when turning left, air will

be forced back into the system.

Right-Hand Truck Gears

B. W

 ith assistance, turn the steering wheel to full right.

Open the bleeder plug one half turn to one (1) turn using

a Hex 8 wrench. With the bleeder still open, turn the

wheels all the way to the left. Confirm the air bubbles

drain through the tube. When you get all the way to the

left, shut the bleeder and torque it to 6.9 N•m – 12.7

N•m. Turn the wheels all the way back to the right and

repeat the procedure four (4) or more times until no air

bubble can be seen through the tube.

NOTE: THE BLEEDER SHOULD ONLY BE OPEN AS YOU

ARE TURNING LEFT! If it is open when turning right, air will

be forced back into the system.

4. C

 enter the steering wheel. The bleeding procedure is

complete.

5. After the air drains completely, fill the power steering

reservoir to the proper level.
4
MASTER AND SLAVE GEAR BLEEDING

PROCEDURE

1. W

 ith the weight of the vehicle on the ground, start the

engine and let it run at idle speed. The drag-link should

be connected to the pitman arm on the main steering

gear, but not connected to the slave gear.

2. T

 urn the steering wheel all the way to the left until the

axle stop contacts the axle and hold pressure on the

steering wheel until the pitman arm on the slave gear

moves its full travel. The steering wheel should move

in the opposite direction of the pitman arm on the main

steering gear. It may be necessary to put a jack under

the steering axle to take some weight off the wheels

for them to turn. Keep holding pressure on the steering

wheel for 15 seconds after the slave gear stops moving.

3. T

 urn the steering wheel all the way to the right until

the axle stop contacts the axle and hold pressure on

the steering wheel until the pitman arm on the slave

gear moves its full travel. Keep holding pressure on

the steering wheel for 15 seconds after the slave gear

stops moving.
NOTE: You must keep pressure on the steering wheel to

keep the valve open and sending fluid to the slave gear.

When the pressure is released, the valve returns to neutral

and no pump pressure is sent to the steering gears.

5. T

 urn the steering wheel until the pitman arm on the slave

gear lines up with the drag-link.

6. I nstall the drag-link. Do not move the pitman arm on the

slave gear by hand. Air may be drawn into the system.

7. C

 ycle the steering gear from stop to stop. If a catch is

noted, look for bleeder plugs on the steering gears. If the

steering gear is mounted with the bulge in the housing

for the sector shaft sitting above the piston cylinder,

follow the procedure outlined for bleeding a single gear

with the bulge in the housing for the sector shaft sitting

above the piston cylinder. If both gears have bleeder

plugs, open the bleeder only when the piston is moving

toward the bleeder.
4. R

 epeat the procedure three (3) more times, or until there

is no air in the system and the slave gear moves freely.
5
© 2021 Bendix Commercial Vehicle Systems LLC, a member of Knorr-Bremse • 9/21 • All Rights Reserved
6

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