ect LEXUS SC300 1991 Service Repair Manual

27. REMOVE FUEL RETURN PIPE(a) Remove the bolt holding the fuel return pipe to the rearside of the LH cylinder head.
(b) Remove the union bolt, two gaskets and return pipe.
28. REMOVE DELIVERY PIPES AND INJECTORS (a) Remove the four nuts holding the delivery pipe to theintake manifold.
(b) Remove the connector bracket, the two delivery pipes, eight injectors assembly, four spacers and eight
insulators.
NOTICE: Be careful not to drop the injectors.
(c) Remove the eight injectors from the delivery pipes.
(d) Remove the O±ring and grommet from each injector.
29. REMOVE INTAKE MANIFOLD Remove the six bolts, four nuts, intake manifold and two gas-
kets.
30. REMOVE FRONT WATER BY±PASS JOINT (a) Disconnect the following connectors:(1) Water temperature sensor connector
(2) Cold start injector time switch connector
(3) Water temperature sender gauge connector
(b) Remove the bolt, and disconnect the engine wire clamp from the water by±pass joint.
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(c) Remove the four nuts, water by±pass joint and twogaskets.
31. REMOVE REAR WATER BY±PASS JOINT (a) Remove the bolt holding the water by±pass pipe to theengine hanger.
(b) Remove the four nuts, water by±pass joint and two gaskets.
32. REMOVE OIL DIPSTICK AND GUIDE FOR ENGINE (a) Remove the mounting bolt.
(b) Pull out the dipstick guide together with the dipstick.
(c) Remove the O±ring from the dipstick guide.
33. REMOVE OIL DIPSTICK AND GUIDE FOR A/T
34. REMOVE EGR PIPE (a) Remove the two nuts holding the EGR pipe to the RHexhaust pipe.
(b) Remove the EGR pipe and gasket.
35. DISCONNECT GROUND STRAP FROM RH CYLINDER HEAD
36. DISCONNECT ENGINE WIRE FROM RH CYLINDER HEAD
Remove the two bolts, and disconnect the engine wire.
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37. DISCONNECT ENGINE WIRE FROM LH CYLINDER HEAD
Remove the five bolts, and disconnect the engine wire.
38. REMOVE ENGINE HANGERS Remove the two bolts and engine hanger. Remove the two
engine hangers.
39. REMOVE CYLINDER HEAD COVERS Remove the eight bolts, seal washers, cylinder head cover
and gasket. Remove the two cylinder head covers.
40. IF NECESSARY, REMOVE SEMI±CIRCULAR PLUGS
41. REMOVE CAMSHAFTS NOTICE: Since the thrust clearance of the camshaft is
small, the camshaft must be held level while it is being
removed. If the camshaft is not kept level, the portion of
the cylinder head receiving the shaft thrust may crack or
be damaged, causing due the camshaft to seize or break.
To avoid this, the following steps should be carried out.
A. Remove exhaust camshaft from RH cylinder head
(a) Bring the service bolt hole of the driven s ub±gear
upward by turning the hexagon wrench head portion of
the exhaust camshaft with a wrench.
(b) Secure the exhaust camshaft sub±gear to the driven
gear with a service bolt.
Recommended service bolt: Thread diameter 6 mm
Thread pitch 1.0 mm
Bolt length 16±20 mm (0.63±0.79 in.)
HINT: When removing the camshaft, make certain that the
torsional spring force of the sub±gear has been eliminated by
the above operation.
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(c) Uniformly loosen and remove the eight bearing capbolts in several passes in the sequence shown.
(d) Remove the four bearing caps, oil seal and intake camshaft.
HINT: Arrange the bearing caps in correct order.
42. DISASSEMBLE EXHAUST CAMSHAFTS (a) M ount the hexagon wrench head portion of the
camshaft in a vise.
NOTICE: Be careful not to damage the camshaft.
(b) Insert a service bolt (A) into the service hole of the camshaft sub±gear.
(c) Using a screwdriver, turn the sub±gear clockwise, and
remove the service bolt (B).
NOTICE: Be careful not to damage the camshaft.
(d) Using snap ring pliers, remove the snap ring.
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(e) Remove the following parts:(1) Wave washer
(2) Camshaft sub±gear
(3) Camshaft gear spring
HINT: Arrange the camshaft sub±gears and gear springs (RH
side and LH side).
43. REMOVE CIRCULAR PLUGS Remove the two bolts, seal washers, bearing cap and circular
plug. Remove the two circular plugs.
HINT: Arrange the bearing caps (RH side and LH side).
44. DISCONNECT MAIN OXYGEN SENSOR CONNECTORS Disconnect the RH and LH oxygen sensor connector.
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45. REMOVE CYLINDER HEADS(a) Uniformly loosen the ten cylinder head bolts on one side
of each cylinder head in several passes in the sequence
shown, then do the other side as shown. Remove the
twenty cylinder head bolts and plate washers.
NOTICE: Head warpage or cracking could result from re-
moving bolts in an incorrect order.
(b) Lift the cylinder heads from the dowels on the cylinder block, and place the two cylinder heads on wooden
blocks on a bench.
HINT: If the cylinder head is difficult to lift off, pry between the
cylinder head and cylinder block with a screwdriver.
NOTICE: Be careful not to damage the contact surfaces
of the cylinder head and cylinder block.
46. REMOVE EXHAUST MANIFOLD FROM RH CYLINDER HEAD
(a) Remove the three bolts and heat insulator.
(b) Remove the main oxygen sensor.
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HINT: Arrange the valve lifters and adjusting shims in correct
order.
2. REMOVE VALVES (a) Using SST, compress the valve spring and remove thetwo keepers.
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(b) Remove the following parts: (1) Spring retainer
(2) Valve spring
(3) Valve
(4) Spring seat
HINT: Arrange 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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INSPECTION, CLEANING AND REPAIR
OF CYLINDER HEAD COMPONENTS
1. CLEAN TOP SURFACES OF PISTONS AND CYLINDERBLOCK
(a) Turn the crankshaft and bring each piston to top deadcenter (TDC). Using a gasket scraper, remove all the
carbon from the piston top surfaces.
(b) Using a gasket scraper, remove all the gasket material from the top surfaces of the cylinder block.
(c) Using compressed air, blow carbon and oil from the bolt
holes.
CAUTION: Protect your eyes when using high±pressure
compressed air.
2. CLEAN CYLINDER HEADS
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.
B. Clean combustion chambers Using 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.
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D. Clean cylinder headsUsing a soft brush and solvent, thoroughly clean the cylinder
heads.
3. INSPECT CYLINDER HEADS
A. Inspect for flatness Using a precision straight edge and feeler gauge, measure
the surfaces contacting the cylinder block and manifolds for
warpage.
Maximum warpage: 0.10 mm (0.0039 in.)
If warpage is greater than maximum, replace the cylinder
head.
B. Inspect for cracks Using 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 any carbon from the valvehead.
(b) Using a wire brush, thoroughly clean the valve.
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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 the diameter measurement of the valve stemfrom the inside diameter measurement of the guide
bushing.
Standard oil clearance:
Intake 0.025±0.060 mm (0.0010±0.0024 in.)
Exhaust 0.030±0.065 mm (0.0012±0.0026 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.
6. IF NECESSARY, REPLACE VALVE GUIDE BUSHINGS (a) Insert an old valve wrapped with tape into the valveguide bushing, and break off the valve guide bushing by
hitting it with a hammer. Remove the snap ring.
HINT: Wrap the tape approx. 8 mm (0.31 in.) from the stem
end.
NOTICE: Be careful not to damage the valve lifter hole.
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