engine LEXUS SC400 1991 Service Repair Manual

8. REMOVE WATER BY±PASS OUTLET AND NO. 1 WATERBY±PASS PIPE
(a) Remove the two bolts, water by±pass outlet and No. 1water by±pass pipe.
(b) Remove the three O±rings from the water by±pass outlet and No. 1 water by±pass pipe.
9. REMOVE WATER OUTLET AND NO. 1 BY±PASS HOSE (a) Remove the two nuts, bolt and water outlet.
(b) Disc onnect the No. 1 by±pass hose from the hose
clamp.
10. REMOVE VACUUM CONTROL VALVE SET AND NO. 2 VACUUM PIPE
(a) Disconnect the two connectors from the VSV.
(b) Disconnect the following hoses:(1) Vacuum hose from ACIS vacuum tank
(2) Three vacuum hoses from VSV
(c) Remove the four nuts, vacuum control valve set and
vacuum pipe.
11. REMOVA OIL DIPSTICK GUIDES FOR ENGINE AND TRANSMISSION (A/T)
(a) Disconnect the fuel return hose from the engine oildipstick guide.
(b) Remove the mounting bolt.
(c) Pull out the dipstick guide together with dipstick. Plug the oil pan.
(d) Remove the O±ring from the dipstick guide.
12. REMOVE AIR INTAKE CHAMBER (a) Remove the bolt, nut and intake chamber stay. Removethe No. 1 and No. 2 stays.
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(b) Disconnect the following hoses:(1) Vacuum hose from brake booster union
(2) Vacuum hose (from ACIS vacuum tank)
(3) Vacuum sensing hose
(4) Air hose (from PS air control valve)
(c) Remove the two bolts, and disconnect the data link connector 1 and harness protector from the air intake
chamber.
(d) Remove the five bolts, two nuts and air intake chamber and gasket.
13. REMOVE DELIVERY PIPE AND INJECTORS (See steps 4, 5, 8 and 10 on pages FI±28 and 29)
14. REMOVE NO. 1 AND NO. 2 FUEL PIPES
15. DISCONNECT ENGINE WIRE FROM INTAKE MANIFOLD (a) Disconnect the following connectors:
(1) Engine coolant temperature sensor connector
(2) Engine coolant temperature sender gauge connec- tor
(3) Two knock sensor connectors
(4) Oil pressure switch connector
(5) Oil level sensor connector
(6) A/C compressor connector
(b) Remove the three nuts and two clamp bolts.
(c) Remove the two bolts, and disconnect the harness
protector from the intake manifold.
16. REMOVE INTAKE MANIFOLD (a) Remove the two bolts and intake manifold stay.
(b) Remove the six bolts, two nuts, intake manifold andgasket.
EM±38
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17. REMOVE NO. 3, No. 1 AND NO. 2 CYLINDER HEADCOVERS
(a) Remove the 12 bolts and four nuts.
(b) Remove the cylinder head covers and gaskets.
18. REMOVE CAMSHAFT TIMING PULLEYS Hold the hexagon portion of the camshaft with a wrench, and
remove the pulley mount bolt and camshaft pulley.
19. REMOVE NO. 4 TIMING BELT COVER Remove the four bolts and timing belt cover.
20. REMOVE CAMSHAFTS (a) Uniformly loosen and remove the four bearing cap bolts.
(b) Using a screwdriver, pry out the two No. 1 camshaft bearing caps and oil seals.
NOTICE: Be careful not to damage the cap. Tape the
screwdriver tip.
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(c) Uniformly loosen and remove the 12 bearing cap boltsin several passes in the sequence shown, and remove
the six bearing caps and camshaft. Remove the intake
and exhaust camshafts.
21. REMOVE CYLINDER HEAD (a) Using a 10 mm bi±hexagon wrench, uniformly loosenand remove the ten cylinder head bolts in several
passes in the sequence shown.
NOTICE: Cylinder head warpage or cranking could result
from removing in incorrect order.
(b) Remove the 14 plate washers.
(c) Lift the cylinder head from the dowels on the cylinder block. As the cylinder head is lifted, separate the heater
water hose from the union.
(d) Place the head on wooden blocks on a bench.
If the cylinder head is difficult to lift off, pry with a screwdriver
between the cylinder head and block projection.
NOTICE: Be careful not to damage the contact surfaces
of the cylinder head and cylinder block.
EM±40
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DISASSEMBLY OF CYLINDER HEAD
(See Components on page EM±35)1. REMOVE VALVE LIFTERS AND SHIMS
HINT: Store the valve lifters and shims in correct order.
2. REMOVE VALVES (a) Using SST, compress the valve spring and remove thetwo keepers.
SST 09202±70010
(b) Remove the spring retainer, valve spring, valve and spring seat.
HINT: Store the valves, valve springs, spring seats and spring
retainers in correct order.
(c) Using needle±nose pliers, remove the oil seal.
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3. REMOVE ENGINE HANGERS
4. REMOVE ENGINE COOLANT TEMPERATURE SENSORAND SENDER GAUGE
5. REMOVE THROTTLE CABLE BRACKET AND GROUND STRAP
6. REMOVE EGR COOLER
INSPECTION, CLEANING AND REPAIR
OF CYLINDER HEAD COMPONENTS
1. CLEAN TOP SURFACES OF PISTONS AND CYLINDER BLOCK
(a) Turn the crankshaft, and bring each piston to top deadcenter (TDC). Using a gasket scraper, remove all the
carbon from the piston top surface.
(b) Using a gasket scraper, remove all the gasket material from the top surface of the cylinder block.
(c) Using compressed air, blow carbon and oil from the bolt
holes.
CAUTION: Protect your eyes when using high±com-
pressed air.
2. CLEAN CYLINDER HEAD
A. Remove gasket material Using a gasket scraper, remove all the gasket material from
the cylinder block surface.
NOTICE: Be careful not to scratch the cylinder block con-
tact surface.
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B. Clean combustion chambersUsing a wire brush, remove all the carbon from the combus-
tion chambers.
NOTICE: Be careful not to scratch the cylinder block con-
tact surface.
C. Clean valve guide bushings Using a valve guide bushing brush and solvent, clean all the
guide bushings.
D. Clean cylinder head Using a soft brush and solvent, thoroughly clean the cylinder
head.
3. INSPECT CYLINDER HEAD
A. Inspect for flatness Using precision straight edge and feeler gauge, measure the
surfaces contacting the cylinder block, intake and exhaust
manifolds for warpage.
Maximum warpage: 0.10 mm (0.0039 in.)
If warpage is greater than maximum, replace the cylinder
head.
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B. Inspect for cranksUsing a dye penetrant, check the combustion chamber, in-
take ports, exhaust ports and cylinder block surface for
cracks.
If cracked, replace the cylinder head.
4. CLEAN VALVES (a) Using a gasket scraper, chip off any carbon from thevalve head.
(b) Using a wire brush, thoroughly clean the valve.
5. INSPECT VALVE STEMS AND GUIDE BUSHINGS (a) Using a caliper gauge, measure the inside diameter ofthe guide bushing.
Bushing inside diameter:
6.010±6.030 mm (0.2366±0.2374 in.)
(b) Using a micrometer, measure the diameter of the valvestem.
Valve stem diameter:
Intake 5.970±5.985 mm (0.2350±0.2356 in.)
Exhaust 5.965±5.980 mm (0.2348±0.2354 in.)
(c) Subtract valve stem diameter measurement from theguide bushing inside diameter measurement.
Standard oil clearance:
Intake 0.025±0.060 mm
(0.0010±0.0024 in.)
Exhaust 0.030±0.065 mm (0.0012±0.0036 in.)
Maximum oil clearance:
Intake 0.08 mm (0.0031 in.)
Exhaust 0.10 mm (0.0039 in.)
If the clearance is greater than maximum, replace the valve
and guide bushing.
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6. IF NECESSARY, REPLACE VALVE GUIDE BUSHINGS(a) Using SST and a hammer, tap out the guide bushing.
SST 09201±70010
(b) Using a caliper gauge, measure the bushing borediameter of the cylinder head.
(c) Select a new guide bushing (STD size or O/S 0.05).
Both intake and exhaust If the bushing bore diameter of the cylinder head is greater
than 11.044 mm (0.4348 in.), machine the bushing bore to
the following dimension:
11.035±11.056 mm (0.4344±0.4353 in.)
If the bushing bore diameter of the cylinder head is greater
than 11.056 mm (0.4353 in.), replace the cylinder head.
(d) Using SST and hammer, tap in a new guide bushing to
the specified protrusion height.
SST 09201±70010
Protrusion height:
Intake 12.3±12.7 mm (0.484±0.500 in.)
Exhaust 11.4±11.8 mm (0.449±0.465 in.)
HINT: Different bushings are used for the intake and exhaust.
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(e) Using a sharp 6 mm reamer, ream the guide bushing toobtain the standard specified clearance (See page
EM±45) between the guide bushing and valve stem.
7. INSPECT AND GRIND VALVES (a) Grind the valve enough to remove pits and carbon.
(b) Check that the valve is ground to the correct valve faceangle.
Valve face angle: 44.5 5
(c) Check the valve head margin thickness.
Standard margin thickness: 0.8±1.2 mm
(0.031±0.047 in.)
Minimum margin thickness: 0.5 mm (0.020 in.)
If the margin thickness is less than minimum, replace the
valve.
(d) Check the valve overall length.
Standard overall length: Intake 98.29±98.79 mm (3.8697±3.8894 in.)
Exhaust 98.84±99.34 mm (3.8657±3.9110 in.)
Minimum overall length: Intake 98.19 mm (3.8657 in.)
Exhaust 98.74 mm (3.8874 in.)
If the overall length is less than minimum, replace the valve.
(e) Check the surface of the valve stem tip for wear.
If the valve stem tip is worn, resurface the tip with a grinder
or replace the valve.
NOTICE: Do not grind off more than the minimum overall
length.
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