engine coolant ACURA NSX 1991 Service Repair Manual

9. Relieve fuel pressure by loosening the service bolt
on the fuel filter about one turn (see section 11).
Do not smoke while working on the
fuel
system.
Keep open flame away from work
area. Drain fuel only into an approved container.
10. Remove the fuel feed pipe and fuel return hose.
11. Remove the wire harness cover, then remove the fuel pipe clamp.

22 N·m
(2.2 kg-m,
16 Ib-ft)

WIRE HARNESS

COVER
6 x 1.0 mm

12 N·m
(1.2 kg-m,

9 lb-ft)

FUEL FEED
PIPE

WASHERS
Replace.

FUEL RETURN

HOSE

12. Remove the brake booster vacuum hose and evapo- rative emission (EVAP) control canister hose.

BRAKE BOOSTER

VACUUM HOSE

EVAP CONTROL

CANISTER HOSE
13. Remove the expansion tank cap.

14. Raise the hoist to full height.
15. Drain the engine coolant (see page
10-5).
Loosen the drain plug from the radiator lower
tank. Remove two drain bolls from the water pipes.
Reinstall the drain bolts with new washers.
Loosen the front and rear engine drain bolts to
drain engine coolant from the cylinder heads.
Connect rubber hoses to the drain bolts.
16. Drain the transmission oil/fluid. Reinstall the drain plug with a new washer.
17. Drain the engine oil. Reinstall the drain plug with a
new washer.

18. Lower the hoist, then remove the air cleaner hous-

ing (see page 6-25 ('91-'93 Mode ls),or('95-'96 Models).

19. Disconnect two hoses, then remove the expansion

tank.

6 x 1.0 mm

10 N·m
11.0 kg-m,

7 lb-ft)

EXPANSION

TANK

WATER BYPASS

HOSES
(cont'd)ProCarManuals.com

Timing Belt

Inspection

1. Remove the ignition coil covers and harness clamps.
2. Disconnect the connectors, then remove the ignition
coils.
3. Remove the cylinder head covers,
4. Inspect the timing belt for cracks and coolant or oil soaking.

NOTE:
Replace the belt if coolant or oil soaked.
Remove any oil or solvent that gets on the belt.

Inspect this area

for wear.

Rotate pulley and

Inspect belt.
Tension Adjustment

CAUTION:
Always adjust timing belt tension with the engine cold
Do not rotate the crankshaft when the adjusting bolt
is loose (the timing belt will skid over the teeth of
the rear intake caimshaft pulley).
Adjust the belt tension only when the belt has been
removed and reinstalled or replaced.

NOTE:
Tensioner is spring-loaded to apply proper tension to
the belt automatically after making the following ad-
justment. Inspect the timing belt before adjusting the belt
tension.
Always rotate the crankshaft clockwise. Rotating it
counterclockwise may result in improper adjustment
of the belt tension or cause the belt to jump a tooth
on the camshaft pulleys.
Install the timing beIt with the No. 1 piston at TDC
(see pages 6-18 ('91-'93) or ('94-'96),19 ('91-'93)
or ('94-'96) Remove the slack in the sequence of , and

by turning each camshaft pulley slightly.
Loosen the timing belt adjusting bolt 180° (the slack
at should be eliminated).

Then, tighten the timing belt adjusting bolt.

Verify that No. 1 piston is at TDC (see page 6-19).
Rotate the crankshaft clockwise nine teeth on the
camshaft pulley (The blue mark on the crankshaft pul- ley should line up with the pointer on lower cover).
Loosen
the
timing
belt
adjusting
bolt.

Retighten the adjusting bolt, torque to 43 N·m (4.3
kg-m, 31 Ib-fl).
Direction

of rotation

POINTER ON
LOWER COVER

ADJUSTING BOLT

43N·m (4.3 kg-m,

31 Ib-ft)
BLUE MARK
TDC MARK
ProCarManuals.com

Cylinder Heads

Illustrated Index (cont'd)
CAUTION:
To
avoid
damage,
wait
until
the
engine
coolant
temperature
drops
below
100°F
(39-C]
before
removing
the
cylin-

der head.

NOTE: Use new O-rings and gaskets when reassembling.

Prior to reassembling, clean all the parts in solvent, dry them, and apply lubricant to any contact parts.

REAR VARIABLE VALVE TIMING
AND VALVE LIFT ELECTRONIC CONTROL
SYSTEM (VTEC) SOLENOID VALVE

Troubleshooting, page 6-3 ('91-'93) or ('94-'96)

EXHAUST GAS
RECIRCULATI0N (EGR) VALVE

6 x 1 .0 mm
12 N·m
(1.2 kg-m.
9 Ib-ft)
8 x
1.25
mm

22 N·m
(2.2 kg-m,
16 Ib-ft)
ENGINE COOLANT
TEMPERATURE (ECT) SENSOR
18 N·m (1.8 kg-m, 13 Ib-ft)

8 x
1.25
mm
22 N·m (2.2 kg-m. 16 lb-ft)
FRONT VTEC SOLENOID VALVE

Troubleshooting. page 6-3

SEALING BOLTS

60 N·m
(6.0 kg-m,

43 lb-ft)

OIL PRESSURE

GAUSE SENDING
UNIT (section 23)

ROCKER

SHAFTS
WASHERS
Replace.

8 x
1.25
mm

22 N·m
(2.2 kg-m,16 Ib-ft)
DOWEL PIN

0-RING

Replace.

ECT SWITCH

28 N·m
12.8 kg-m.

20 lb-ft

O-RING

Replace.

O-RING

Replace.

ROCKER ARM ASSEMBLY[PRIMARY. MID, SECONDARY]

Inspection, page 6-32 ('91-'93) or ('94-'96)

ROCKER SHAFT

OIL CONTROL
ORIFICE

Remove with 5 mm

boit and clean.

FILTER
Replace.

GASKET

Replace.

O-RING

Replace.ProCarManuals.com

Cylinder Heads

Removal

Engine removal is not required for this procedure. Make sure jacks and safety stands are
placed properly and hoist brackets ere attached to cor- rect positions on the engine.
CAUTION: Use a fender cover (special tool) to avoid damaging
painted surfaces. Unplug the wiring connectors carefully while holding
the connector portion to avoid damage.
To avoid damaging the cylinder heads, wait until the
engine coolant temperature drops below 100°F
(38°C) before loosening the retaining bolts. Do not open the engine cover when the roof panel is
stored (NSX-T open top).
NOTE:
Unspecified items are common.

Mark all wiring and hoses to avoid misconnection.
Also, be sure that they do not contact other wiring or

hoses or interfere with other parts.

Inspect the timing belt before removing the cylinder

head.

Turn the crankshaft pulley SO that the No. 1 piston is at top dead center (see page 6-19 ('91-'93) or ('94-'96)).
1. Disconnect the negative terminal from the battery.
2. Remove the expansion tank cap. Use care when removing the expan-
sion tank cap to avoid scalding by engine coolant
or steam.
3. Raise the car, then remove the right rear wheel/tire.
4. Drain the engine coolant (see page 10-5 ). 5. Remove the engine under guard, then remove the
front exhaust pipe A.

GASKETS
Replace.

FRONT EXHAUST

PIPE A

SELF-LOCKING NUT

10 x
1.25
mm

55 N·m (5.5 kg-m, 40 Ib-ft)
Replace.
SELF- LOCKING NUT

8 x
1.25
mm

22 N·m (2.2 kg-m. 16 Ib-ft)

Replace.

6. Remove the rear exhaust pipe A.

SELF- LOCKING NUT

8 x
1.25
mm
22 N·m (2.2 kg-m, 16 Ib-ft)

Replace.

REAR

EXHAUST

PIPE A

SELF-LOCKING NUT
10 x
1.25
mm

55 N·m (5.5 kg-m.

40 Ib-ft)

Replace.
GASKETS

Replace.

7. Remove the engine oil cooler base assembly (see
page 6-15 ('91-'93) or ('94-'96).

8. Lower the car.
9. Remove the strut brace (see page 5-3 ).ProCarManuals.com

24. Remove the engine wire harness connectors and
wire harness clamps from the cylinder head and
intake manifold, Six injector connectors
Intake air temperature (IAT) sensor connector
CKP/CYP sensor connector
Heated oxygen sensor (HO2S) connectors

Ignition control module (ICM) connectors

Engine coolant temperature (ECT) sensor connec-

tor

ECT gauge sending unit connector
ECT switch connector
Exhaust gas recirculation (EGR) valve lift sensor

connector

Throttle position sensor connector Engine oil pressure gauge sending unit connector
Knock sensor connector
VTEC solenoid valve connectors
VTEC pressure switch connectors
Engine oil pressure switch connector
Alternator connector

Alternator terminal

Throttle body 6P connector

25. Remove the ignition coils and connector.

26. Remove the EGR pipe and intake manifold assem- bly.

8 x 1.25mm

22 N·m (2.2 kg-m, 16 Ib-ft)

6 x 1.0 mm
12 N·m
(1.2 kg-m,

9 lb-ft)

GASKETS

Replace. INTAKE
MANIFOLD
ASSEMBLY

GASKET
Replace.
27. Loosen the adjusting nut and idler pulley center nut,
then remove the air conditioning compressor belt

(see page 6-17('91-'93) or ('94-'96)).

28. Remove the cover, adjusting bolt, mounting bolt and mounting nut, then remove the alternator belt
and alternator.

COVER

MOUNTING BOLT
10 x
1.25
mm

45 N·m (4.5 kg·m,

33 Ib-ft)

MOUNTING NUT
10 x
1.25
mm

45 N·m (4.5 kg·m.

33 Ib·ft)
ALTERNATOR

BELT

29. Disconnect the knock sensor connector, then remove
the wire holder.

6 x 1.0 mm
12N·m (1.2 kg-m, 9 Ib-ft)

KNOCK SENSOR
WIRE HOLDER
(cont'd)

6 x 1.0 mm

12 N·m (1.2 kg-m, 9 Ib-ft)

ADJUSTING

BOLTProCarManuals.com

Cooling
Illustrated Index
Syste m is unde r hig h pressur e whe n th e
engin e i s hot . T o avoi d dange r o f releasin g scaldin g
engin e coolant , remov e th e ca p onl y whe n th e engin e i s
cool .
Tota l Coolin g Syste m Capacity : Includin g expansio n
tank 2. 1 (2. 2 U S qt . 1. 8 Im p qt )
5 M/T : 16. 0 (17. 0 US qt , 14. 1 Imp qt )
4 A/T : 16. 5 (17. 4 US qt , 14. 5 Imp qt )
NOTE :
• Chec k al l coolin g syste m hose s fo r damage ,
leak s o r deterioratio n an d replac e i f necessary .
• Chec k al l hos e clamp s an d retighte n i f
necessary .
• Us e ne w O-ring s whe n reassembling .
Radiator, Wate r Pipe s an d Hoses :
BLEED BOL T10 N- m (1. 0 kg-m ,7 Ib-ft )
WASHE RReplace .
HEATER PIP E
RADIATO R
LOWE R HOS E
RADIATO R
UPPE R HOS E
RADIATO REngine coolan t refillin g an dbleeding , pag e 10- 5Leak test , pag e 10- 8Inspec t soldere d joint s an dseam s fo r leaks .Blow ou t dir t fro m betwee ncore fin s wit h compresse d air .If insects , etc. , ar e cloggin gradiator, was h the m of f wit hlow-pressur e water . BLEE
D PLU G
RESISTO R
RADIATO R DRAI N
PLU G
FRON T LOWE R
WATE R PIP E
FRON T UPPE R
WATE R PIP E FA
N SHROU D
5 x 0. 8 m m4.5 N- m (0.4 5 kg-m , 3. 3 Ib-ft )
Replace .
BLEED BOL T
10 N- m (1. 0 kg-m ,7 Ib-ft )
WASHER S
Replace .
WATER PIP E
DRAI N BOLT S
15 N- m (1. 5 kg-m , 1 1 Ib-ft )
WATE RPIPE ASSEMBL YWASHE
RReplace .
FAN MOTO R
ProCarManuals.com

Engine Coolant Refilling and Bleeding

CAUTION: When pouring engine coolant, be sure to

shut the relay box lid and not let coolant spill on the

electrical parts or the paint. If any coolant spills, rinse it

off immediately.

NOTE:

• Perform this maintenance when the engine is cool.

• Before replacing the coolant, turn the ignition ON,

slowly turn the climate control temperature knob to

90° and turn off the ignition. This will allow the

coolant in the heater to drain out with the rest of the

system.
1. Open the hood, the rear window and the engine

cover.

2. Remove the cover protecting the water pipes and

shift cables on the underside of the car.

3. Before removing the expansion tank cap, first

loosen the cap to lower pressure.

CAUTION: Do not remove the expansion tank cap

when engine is hot. The coolant is under pressure

and may blow out and scald you. Open the cap

slowly when the engine is cool.

4. Loosen the drain plug in the bottom of the radiator,

and drain the coolant.

5. Remove the two drain bolts from the water pipes,

and drain the coolant.

WASHERS

Replace.

DRAIN BOLTS

15 N-m (1.5 kg-m, 11 Ib-ft)
DRAIN HOLE
DRAIN PLUGProCarManuals.com

Radiator
Engine Coolan t Refillin g an d Bleedin g
6. Instal l rubbe r hose s o n th e drai n bolt s a t th e fron t
an d rea r of the engin e unde r th e cylinde r banks .
Loose n th e drai n bolt s t o drai n th e coolant .
• Drainin g ca n b e don e mor e quickl y i f al l th e blee d
bolt s an d plu g ar e als o opened . Befor e openin g
them , mak e sur e th e coolan t leve l i n th e expan -
sio n tan k ha s com e dow n completel y s o tha t th e
coolan t wil l no t pou r ou t o f th e blee d bolt s an d
plug .
7. Whe n th e coolan t stop s draining , tighte n th e
radiato r drai n plug , wate r pip e drai n bolt s an d
engin e drai n bolts .
• B e sur e t o replac e th e wate r pip e drai n bol t
washer s wit h ne w ones .
REAR ENGIN E DRAI N BOL T
3 0 N- m (3. 0 kg-m , 2 2 Ib-ft )
8. Ope n al l fou r bleeders .
1 ) Loose n th e radiato r blee d plug .
2 ) Remov e th e heate r pip e blee d bolt .
3 ) Loose n th e wate r pip e blee d bolt .
4 ) Loose n th e engin e blee d bol t o n th e therm o
cover.
9. Mi x th e recommende d antifreeze/coolan t wit h a n
equa l amoun t o f wate r i n a clea n container .
NOTE:
• Us e onl y Honda-recommende d anti-freeze /
coolant.
• Fo r bes t corrosio n protection , th e coolan t con -
centration s mus t b e maintaine d year-roun d a t
50 % minimum . Coolan t concentration s les s tha n
50 % ma y no t provid e sufficien t protectio n
agains t corrosio n o r freezing .
• Coolan t concentration s greate r tha n 60 % wil l
impai r coolin g efficienc y an d ar e no t recom -
mended.
CAUTION :
• D o no t mi x differen t brand s o f anti -
freeze/coolant .
• D o no t us e additiona l rus t inhibitor s o r anti-rus t
products ; the y ma y no t b e compatibl e wit h th e
recommende d coolant .
Engin e Coolan t Refil l Capacity : Includin g expansio n
tank 2. 1 (2. 2 U S qt , 1. 8 Im p qt )
Manual : 12. 0 (12. 7 U S qt , 10. 6 Im p qt )
Automatic : 12. 0 (12. 7 U S qt , 10. 6 Im p qt )
FRON T ENGIN E DRAI N BOL T30 N- m (3. 0 kg-m , 2 2 Ib-ft )
ProCarManuals.com

10. Fil l th e expansio n tan k wit h engin e coolant . A s
coolan t start s t o ru n ou t i n a stead y strea m withou t
bubbles , tighte n th e bleeder s i n sequence : therm o
cove r blee d bolt , radiato r blee d plug , heate r pip e
blee d an d wate r pip e blee d bolt .
11 . Afte r tightenin g al l th e bleedin g bolt s an d plug , fil l
th e expansio n tan k wit h coolan t u p t o th e MA X line .
12. Loose n th e therm o cove r blee d bol t t o remov e an y
remainin g air .
13 . Whe n bleedin g i s completed , retighte n th e therm o
cove r blee d bol t an d fill the expansio n tan k u p t o
0. 5 (0.5 3 US qt , 0.4 4 Imp qt ) o r 3 0 m m (1. 2 in)
ove r th e MA X line . 14
. Instal l th e expansio n tan k cap , an d tur n it 6 0 degree s
(wher e it engage s th e firs t loc k ta b o f fille r neck) .
1 5 . Star t th e engine , an d le t i t ru n unti l warme d u p (unti l
th e thermosta t open s an d th e radiato r coolin g fa n
runs) .
16. Tur n of f th e engine . Chec k th e expansio n tan k and ,
i f needed , ad d engin e coolan t t o brin g i t u p t o th e
MA X line .
17. Tighte n th e expansio n tan k ca p securely .
18 . Reinstal l th e cove r o n th e car' s underside .
THERMO COVE R
BLEE
D PLU G
RADIATO
R UPPE R
TAN K HEATE
R PIP E
BLEED BOL T
10 N- m (1. 0 kg-m ,7 Ib-ft )
BLEE
D BOL T
10 N- m (1. 0 kg-m ,7 Ib-ft )
BLEE
D BOL T
10 N- m (1. 0 kg-m ,7 Ib-ft )
ProCarManuals.com

Inspection


Replacement
1. Remove the timing belt (see page 6-15) ('91-'93) or

('94-'96).

2. Check that the water pump pulley turns counterclock-

wise.

3. Check for signs of seal leakage.
NOTE: A small amount of "weeping" from the bleed
hole is normal.

Turns
counterclockwise

BLEED HOLE
BLEED HOLE

1. Remove the timing belt (see page 6-15 ('91-'93) or
('94-'96).

2. Unscrew the bolts, then remove the water pump.
NOTE: Inspect and clean the 0-ring groove and
mating surface with the cylinder block.

DOWEL PIN
SPECIAL BOLTS
6 x 1.0 mm: 7 BOLTS
12 N·m

(1 .2 kg-m, 9 Ib-ft)

Replace,

WATER PUMP
0-RING

Replace.
SPECIAL BOLTS
8 x 1.25 mm: 2 BOLTS

22 N·m
(2.2 kg-m,
16 Ib-ft)
Replace.

3. Install the water pump in the reverse order of
removal.

NOTE:
Keep the 0-ring in position when installing.
Clean up spilled engine coolant.ProCarManuals.com