LEXUS LS430 2003 Factory Repair Manual

Fig. 317: Removing Carbon From Combustion Chambers
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3. Using a valve guide bushing brush and solvent, clean all the guide bushes.

Fig. 318: Cleaning All Guide Bushes
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4. Using a soft brush and solvent, thoroughly clean the cylinder head.

Fig. 319: Cleaning Cylinder Head Using Soft Brush
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Fig. 320: Inspecting Cylinder Head Warpage
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b. Inspect the cylinder head warpage.
1. Usin
g a precision straight edge and feeler gauge, measure the surfaces contacting the cylinder

block and the manifolds for warpage.
MAXIMUM WARPAGE:
CYLINDER BLOCK CONTACTING SURFACE SPECIFICATIONS
If the warpage is greater than the maximum, replace the cylinder head.
Fig. 321: Inspecting Cylinder Head For Cracks

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c. Inspect the cylinder head for cracks.
1. Using a dye penetrant, check the combustion chamber, intake ports, exhaust ports and cylinder
block surface for cracks.
If cracked, replace the c
ylinder head.
ItemSpecified Condition
Cylinder block surface0.05 mm (0.0020 in.)
Intake manifold surface0.10 mm (0.0039 in.)
Exhaust manifold surface0.10 mm (0.0039 in.)

Fig. 322: Cleaning Valves
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6.INSPECT INTAKE VALVE
a. Clean the valves.
1. Using a gasket scraper, chip off any carbon from the valve head.
2. Usin
g a wire brush, thoroughly clean the valve.

Fig. 323: Measuring Diameter Of Valve Stem Using Micrometer
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b. Using a micrometer, measure the diameter of the valve stem.
Valve stem diameter:
5.470 to 5.485 mm (0.2154 to 2.2159 in.)
If the diameter is
greater than the maximum, replace the valve and guide bushing.

Fig. 324: Checking Valve Face Angle
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c. Check the valve face angle.
1. Grind the valve enough to remove pits and carbon.
2. Check that the valve is ground to the correct valve face angle.
Valve face angle: 44.5°
If the valve face is worn, replace the valve.

Fig. 325: Checking Valve Head Margin Thickness
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d. Check the valve head margin thickness.
Standard margin thickness: 1.0 mm (0.039 in.)
Minimum margin thickness: 0.5 mm (0.020 in.)
If the mar
gin thickness is less than the minimum, replace the valve.

Fig. 326: Checking Valve Overall Length
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e. Check the valve overall len
gth.