1991 LEXUS SC300 oil

(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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ENGINE MECHANICAL Cylinder HeadsEM±69
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(c) Set the timing mark (one dot mark) of the camshaftdriven gear at approx. 105 angle by turning the hexagon
wrench head portion of the exhaust camshaft with a
wrench.
(d) Alternately loosen and remove the two bearing cap bolts
holding the intake camshaft side of the oil feed pipe to
the cylinder head.
(e) Uniformly loosen and remove the eight bearing cap bolts in several passes in the sequence shown.
(f) Re mo ve th e oil fe e d pip e , fo u r be a rin g ca p s an d
exhaust camshaft.
B. Remove intake camshaft from RH cylinder head (a) Remove the rear bearing cap.
(b) Set the timing mark ( one dot mark) of the camshaft drive
gear at approx. 455 angle by turning the hexagon
wrench head portion of the intake camshaft with a
wrench.
(c) Uniformly loosen and remove the eight bearing cap bolts in several passes in the sequence shown.
(d) Remove the four bearing caps, oil seal and intake
camshaft.
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ENGINE MECHANICAL Cylinder HeadsEM±71
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C. Remove exhaust camshaft from LH 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.
(c) Set the timing mark (two dot marks) of the camshaft
driven gear at approx. 155 angle by turning the hexagon
wrench head portion of the exhaust camshaft with a
wrench.
(d) Alternately loosen and remove the two bearing cap bolts
holding the intake camshaft side of the oil feed pipe to
the cylinder head.
(e) Uniformly loosen and remove the eight bearing cap bolts in several passes in the sequence shown.
(f) Re mo ve th e oil fe e d pip e , fo u r be a rin g ca p s an d
exhaust camshaft.
D. Remove intake camshaft from LH cylinder head (a) Remove the front bearing cap.
(b) Set the timing mark ( one dot mark) of the camshaft drive
gear at approx. 605 angle by turning the hexagon
wrench head portion of the intake camshaft with a
wrench.
EM±72
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ENGINE MECHANICAL Cylinder Heads
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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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ENGINE MECHANICAL Cylinder HeadsEM±73
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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.
SST 09202±70010
(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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ENGINE MECHANICAL Cylinder HeadsEM±77
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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.
EM±78
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ENGINE MECHANICAL Cylinder Heads
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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.
EM±80
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ENGINE MECHANICAL Cylinder Heads
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10. INSPECT CAMSHAFTS AND BEARINGS
A. Inspect camshaft for runout(a) Place the camshaft on V±blocks.
(b) Using a dial indicator, measure the circle runout at thecenter journal.
Maximum circle runout: 0.08 mm (0.0031 in.)
If the circle runout is greater than maximum, replace the cam-
shaft.
B. Inspect cam lobes Using a micrometer, measure the cam lobe height.
Standard cam lobe height:
Intake 41.710±41.810 mm (1.6421±1.6461 in.)
Exhaust 41.910±42.010 mm (1.6500±1.6539 in.)
Minimum cam lobe height: Intake 41.56 mm (1.6362 in.)
Exhaust 41.76 mm (1.6441 in.)
If the cam lobe height is less than minimum, replace the cam-
shaft.
C. Inspect camshaft journals Using a micrometer, measure the journal diameter.
Journal diameter:
Exhaust camshaft thrust portion (A) 23.959±23.975 mm
(0.9433±0.9439 in.)
Others 26.954±26.970 mm (1.0612±1.0618 in.)
If the journal diameter is not as specified, check the oil clear-
ance.
D. Inspect camshaft bearings Check the bearings for flaking and scoring.
If the bearings are damaged, replace the bearing caps and
cylinder head as a set.
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ENGINE MECHANICAL Cylinder HeadsEM±85
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