1995 ACURA TL steering

System Description

System Operation (cont'd)

Hydraulic Control at Each Speed Range

When stopped:

When the vehicle is stopped with the engine idling, the fluid flow is shut off because the power steering speed sensor

rotor is not rotating. The standard pressure generated by the pressure control valve is applied to the assist control valve to

move the valve to the left. When the assist control valve is in this position, the orifice valve is closed. Therefore, the fluid

discharged from the pump is fed to the low speed valve of the valve body unit. Because the low speed valve has the small

chamfer and thereby the small opening angle, the large hydraulic pressure (steering rack thrust) results in the smallest

steering force (high assist).

HIGH SPEED FEED PASSAGE

LOW SPEED FEED PASSAGE
ASSIST CONTROL VALVE UNIT

POWER STEERING SPEED

SENSOR SIGNAL PRESSURE

HIGH SPEED

VALVE

SLEEVE

TORSION BAR

INPUT SHAFT

VALVE BODY UNIT

SENSOR ORIFICE

ASSIST VOLUME: LIGHT

STEERING WITH VEHICLE PARKED

ROAD SURFACE RESISTANCE

SMALL
LARGE
FLOW: O (ZERO)

LOW SPEED

VALVE

POWER STEERING SPEED

SENSOR AT A STOP
RESERVOIR
PUMP
FULL CLOSE

PRESSURE CONTROL VALVE
(HIGH)
ASSIST CONTROL

VALVEProCarManuals.com

Middle speed range:

When the vehicle starts to move, the power steering speed sensor rotor starts to rotate as well, reducing the standard

pressure and generating the power steering speed sensor signal pressure. The valve returns to the right point where the

pressure of the power steering speed sensor signal equals the spring force of the assist control valve. When the assist

control valve is in this position, the orifice of the valve slightly opens.

Therefore, the fluid pressure from the pump is applied to the high speed valve of the valve body unit. Because the high

speed valve has a larger chamfer and the compound opening area with the low speed valve is larger than that when the

vehicle is stopped, the fluid pressure (steering rack thrust) is not generated unless the displacement angle is large (large

steering torque), resulting in moderately heavy steering (medium assist).

FLOW: MIDDLE
ASSIST CONTROL VALVE UNIT

POWER STEERING SPEED

SENSOR SIGNAL PRESSURE (MEDIUM)

MIDDLE POWER STEERING SPEED

SENSOR ROTATION SPEED

MODERATELY HEAVY STEERING

IN MIDDLE SPEED RANGE
SMALL
ROAD SURFACE

RESISTANCE LARGE

High speed range:

When the vehicle is driven at high speed, the power steering speed sensor rotor rotates at a high speed, greatly reducing

the standard pressure. The pressure of the power steering speed sensor signal is at the lowest value, and the assist con-

trol valve is at the right end position.

When the assist control valve is in this position, the orifice of the valve opens fully. Therefore, the fluid pressure applied to

the high speed valve is larger than when the engine speed is at the middle speed range. The compound opening area with

the low speed valve is the largest this time, and the fluid pressure (steering rack thrust) is not generated unless the dis-

placement angle is very large (low assist).

FLOW: LARGE
ASSIST CONTROL VALVE UNIT

POWER STEERING SPEED

SENSOR SIGNAL PRESSURE (LOW)

HIGH POWER STEERING SPEED

SENSOR ROTATION SPEED

LOW ASSIST: ADEQUATELY HEAVY

STEERING IN HIGH SPEED RANGE
SMALL
-ROAD SURFACE

RESISTANCE LARGE
PRESSURE CONTROL VALVE

SENSOR ORIFICE
HALF OPEN
ASSIST CONTROL

VALVE

VALVE BODY UNIT

ASSIST CONTROL

VALVE

FULL OPEN

SENSOR ORIFICE
PRESSURE CONTROL VALVEProCarManuals.com

Troubleshooting
General Troubleshootin g
Check th e followin g befor e yo u begin :
Has th e suspensio n bee n modifie d in a wa y tha t woul d affec t steering ?
Are tir e sizes , tir e variet y an d ai r pressur e correct ?
Is th e steerin g whee l origina l equipmen t o r equivalent ?
Is th e powe r steerin g pum p bel t properl y adjusted ?
Is steerin g flui d reservoi r fille d to prope r level ?
Is th e engin e idl e spee d correc t an d steady ?
Hard Steerin g (D o powe r assis t check , se e pag e 17-20 . I f th e figur e is ove r 2 4 N (2. 4 kgf , 5. 3 Ibf) , follo w th e nex t steps )
Chec k pum p flui d pressur e (se e
pag e 17-25 ).
Measur e steady-stat e flui d pres -
sur e whil e idlin g wit h bot h valve s
fully open .It shoul d b e 1,50 0 kP a (1 5 kgf /cm2, 21 3 psi ) o r below .
Abnorma l flui dpressur e (flui d
pressur e is to o
high ) Chec
k th e fee d an d retur n circui t line s an d hos e
betwee n th e gearbo x an d pum p fo r cloggin g an d
deformation .
Norma l Norma
l pip e an d hos e
Fault y valv e bod y uni t
Chec k pum p flui d pressur e (se e
page 17-25 ).Measur e pum p relie f pressur ewhile idlin g wit h th e pressur econtrol valve full y closed .
I t shoul d b e 7,80 0 - 8,80 0 kP a (8 0
- 9 0 kgf/cm
2, 1,13 8 - 1,28 0 psi ) Relie
f pressur e
too lo w
Norma l relie f pressur e
G o to pag e 17-1 3 Norma
l
Fault y pum p assembl y Abnorma
l
Fault y flo w contro l valv e
Chec
k th e flo w contro l valv e (se e pag e 17-38 ).
• Chec k th e valv e fo r smoot h movemen t i n th e hous -
ing.• Chec k th e relie f valv e fo r leaks .
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From pag e 17-1 2
Chec k forc e require d t o tur n th e
whee l (se e pag e 17-20 ).
Star t th e engin e an d measur e
force require d t o tur n th e whee lto th e righ t an d left . Differenc e o fth e forc e require d t o tur n th ewhee l t o th e righ t an d t o th e lef tshoul d b e 2. 9 N (0. 3 kgf , 0. 7 Ibf )
o r below . Abnorma
l
Check cylinde r pipe s A an d B fo r deformation .
Norma l No
t deforme d
Faulty valv e bod y uni t
Deforme d
Faulty cylinde r pip e
Measur e th e forc e require d t o
tur n th e whee l wit h th e powe r
steerin g spee d senso r hos e
plugge d an d th e vehicl e parke d(see pag e 17-20 ).
Abnorma l
Steering effor t belo w 2 4 N (2. 4 kgf , 5. 3 Ibf) . Connec t
th e senso r hos e a s it is .
I f th e steerin g effor t i s abov e 2 4 N (2. 4 kgf , 5. 3 Ibf) ,
replac e th e powe r steerin g spee d sensor .
Steerin g effor t abov e 2 4 N (2. 4 kgf , 5. 3 Ibf) . Chec k
th e assis t contro l valv e fo r stickin g o r a clogge d ori -
fice ; clea n th e valv e a s necessar y (se e pag e 17-55 ).
Assis t contro l valv e is norma l
Chec k th e gearbox .
Remov e th e gearbo x an d mea -
sur e th e pinio n torque .
Th e torqu e shoul d be ;
* 0. 6 - 1. 2 N- m (6 - 1 2 kgf-cm , 5. 2
- 1 0 Ibf-in ) wit h th e steerin g rac k
i n th e straigh t drivin g position .
* 1. 3 N- m (1 3 kgf-cm , 11. 3 Ibf-in )with th e steerin g rac k i n an y
othe r position .
Normal
Check th e part s othe r tha n th e gearbox-relate d part s fo r
prope r rotation .
• Imprope r rotatio n o f th e steerin g column-relate d part(s )
• Fault y steerin g join t
• Fault y rac k end/tie-ro d en d bal l joint s
• Interferenc e in th e steerin g syste m
Abnorma l
Adjus t th e rac k guid e (se e pag e
17-24 ), an d rechec k th e pinio n
torque.
Norma l Improperl y adjuste d rac k guid e
Abnorma l
Faulty gearbo x
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Troubleshooting
General Troubleshootin g (cont'd )
Assist (excessivel y ligh t steering ) a thig h speed . Chec
k th e rac k guid e fo r prope r
adjustmen t (se e pag e 17-24 ).
Measur e forc e require d t o tur n
whee l wit h bypas s tub e join tinstalled , an d th e vehicl e parke d o n
dr y pave d surfac e (se e pag e 17-21 ). I
f th e proble m is no t correcte d b y
adjustin g th e rac k guide , adjus tthe fron t whee l alignmen t (se e
sectio n 18 ).
I f belo w th e specifications , chec k
th e powe r steerin g spee d sensor ,
assis t contro l valve , pressur e
contro l valv e an d valv e bod y uni t
fo r stickin g o r a clogge d orifice .
Shoc k o r vibratio n whe n whee l i s
turne d t o ful l lock . Chec
k th e rac k guid e fo r prope r
adjustmen t (se e pag e 17-24 ).
Rac k guid e is adjuste d properly .
Chec k th e bel t fo r slippag e an d
adjus t a s necessar y (se e pag e
17-23 ).
Rac k guid e wa s backe d of f exces -sively.
Adjus t th e rac k guide .
I f th e proble m is no t correcte d b y
adjustin g th e rac k guide , replac e
th e gearbox .
Steering whee l wil l no t retur nsmoothly . Chec
k cylinde r line s A an d B fo r
deformation .
A an d B cylinde r line s ar e nor -mal, chec k whee l alignmen t (se e
sectio n 18 ).
Whee l alignmen t i s normal .
Remov e th e gearbo x fro m th e
fram e an d measur e th e pinio n
torqu e o n th e gearbox . A
o r B cylinde r lin e i s deformed ;
replac e it .
Whee l alignmen t i s abnormal ,
adjus t a s needed .
I t shoul d b e 0. 7 - 1. 2 N- m (7 -
1 2 kgf-cm , 6-1 0 Ibf-in ) o r les s
wit h th e steerin g rac k i n th e
straigh t ahea d drivin g position .
1. 3 N- m (1 3 kgf-cm , 11. 3 Ibf-in )
wit h th e steerin g rac k i n an y
othe r position .
I f th e measurement s ar e ou t o f
specifications , adjus t th e rac k
guide .
I f th e proble m is no t correcte d b y
adjustin g th e rac k guide , replac ethe gearbox .
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Uneven o r roug h steering .
Improperly adjuste d rac k guide .
Bel t slippin g o n pulley .
Idl e spee d lo w o r erratic .
Ai r i n reservoir , o r chec k powe r
steerin g flui d level . Adjus
t rac k guid e (se e pag e 17-24 ).
I f th e proble m is no t correcte d b y
adjustin g th e rac k guide , replac e
th e gearbox .
Adjus t bel t tension . Replac e th e
belt , i f necessar y (se e pag e 17-23 ).
I f th e engin e stall s whe n th e whee l
i s turne d whil e vehicl e i s stoppe d
o r movin g a t lo w speed , adjus t idl e
speed (see section 11).
Check powe r steerin g flui d level . I f
leve l i s excessivel y low , chec k fo r
leak s i n th e system . Ad d flui d t o
th e specifie d level .
I f flui d leve l i s OK , chec k O-ring s
an d seal s o n bot h end s o f th e
pum p inle t hose , an d th e P/ S
pum p housin g matin g surface s
an d th e pum p shaf t oi l sea l fo r
suctio n leaks . Replac e part s a s
necessary .
Steering whee l kick s bac k
durin g wid e turns . Pum
p bel t slippin g o n pulle y
(pum p stop s momentarily) .
Instal l th e powe r steerin g pressur e
gauge . Clos e th e pressur e contro l
valv e full y an d measur e th e pum p
pressur e (se e pag e 17-25 ).
Adjus t bel t tensio n (se e pag e
17-23 ) o r replac e belt .
Chec k if pum p pressur e is norma l
an d th e gaug e needl e trave l i s 50 0
kP a ( 5 kgf/cm
2, 7 1 psi ) o r less .
Chec k th e flo w contro l valv e if th e
needl e trave l exceed s 50 0 kP a ( 5
kgf/cm
2, 7 1 psi) . I f th e flo w contro l
valv e i s normal , replac e th e pum p
a s a n assembly .
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Inspection an d Adjustmen t
Steering Operatio n
Place th e fron t wheel s i n th e straigh t ahea d position ,
an d measur e th e distanc e th e steerin g whee l ca n b e
turne d withou t movin g th e fron t wheels .
ROTATIONA L PLAY : 0 - 10 m m (0 - 0.3 9 in )
If th e pla y exceed s the servic e limit, perfor m rack guid e
adjustmen t (se e pag e 17-24 ).
I f th e pla y i s stil l excessiv e afte r rac k guid e adjustment ,
inspec t th e steerin g linkag e an d gearbo x a s describe d
o n th e nex t page .
ROTATIONA L PLA Y
Powe r Assis t Chec k wit h Vehicl e
Parked
1. Chec k th e powe r steerin g flui d leve l (se e pag e 17-24 )
an d pum p bel t tensio n (se e pag e 17-23 ).
2 .
3 .
Star t th e engine , allo w it t o idle , an d tur n th e steer -
in g whee l fro m lock-to-loc k severa l time s t o war m
up th e fluid .
Attac h a sprin g scal e to th e steerin g wheel . Wit h th e
engin e idlin g an d th e vehicl e o n a clean , dr y floor ,
pul l th e scal e a s shown . Rotat e th e steerin g whee l
more tha n 9 0 degre e angl e b y pullin g th e sprin g
scale. Rea d th e figur e o n th e sprin g scal e whil e th e
steerin g whee l i s i n motion .
SPRING SCAL E(Commerciall y available )
A. Th e scal e shoul d rea d n o mor e the n 2 4 N (2. 4 kgf ,
5.3 Ibf) .
If i t read s more , g o o n t o ste p 5 .
5 . Sto p th e engine . Disconnec t th e hos e fro m th e
powe r steerin g spee d sensor , an d plu g th e hos e
an d th e senso r fittin g a s shown .
PLUG
POWE R STEERIN GSPEED SENSO R
6. Star t th e engine , an d le t i t idle .
I f th e readin g is no w 2 4 N (2. 4 kgf , 5. 3 Ibf ) o r less ,
connec t th e senso r hos e a s i t is . I f th e steerin g
effor t i s abov e 2 4 N (2. 4 kgf , 5. 3 Ibf) , replac e th e
powe r steerin g spee d senso r (se e pag e 17-25 ).
I f th e readin g i s stil l mor e tha n 2 4 N (2. 4 kgf , 5. 3
Ibf) , chec k th e gearbo x an d pump .
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Inspection an d Adjustmen t
Steering Linkag e an d Gearbo x
STEERIN G COLUM NInspect fo r loos e colum n
mountin g bolt s an d nuts .
BOO TInspec t fo r damag e an d deterioration .
STEERING JOINT SCheck fo r loos e join t bolts .
TIE-RO D LOCKNU TCheck fo r loos e locknut .
STEERIN G GEARBO XInspect fo r loos e mountin g bolts .BALL JOIN T BOO T
Inspec t fo r damag e an d deterioration .
Se e pag e 17-6 9 fo r replacement .
TIE-RO D EN D BAL L JOIN T
Inspec t fo r fault y movemen t
and damage .
GEARBO X MOUNTIN G CUSHION SInspect fo r deterioration .
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