Last Modified: 08-21-2023 6.11:8.1.0 Doc ID: RM100000001AODC
Model Year Start: 2019 Model: Avalon HV Prod Date Range: [04/2018 -           ]
Title: A25A-FXS (ENGINE MECHANICAL): CYLINDER HEAD: INSPECTION; 2019 - 2022 MY Avalon HV [04/2018 -        ]

INSPECTION

PROCEDURE

1. INSPECT CYLINDER HEAD SUB-ASSEMBLY

(a) Using a precision straightedge and feeler gauge, measure the warpage of the contact surfaces where the cylinder head sub-assembly contacts the cylinder block sub-assembly, intake manifold and exhaust manifold (TWC: Front Catalyst).

*a

Bottom Side

*b

Intake Manifold Side

*c

Exhaust Manifold (TWC: Front Catalyst) Side

-

-

Maximum Warpage:

Item

Specified Condition

Bottom side

0.05 mm (0.00197 in.)

Intake manifold side

0.10 mm (0.00394 in.)

Exhaust manifold (TWC: Front Catalyst) side

0.10 mm (0.00394 in.)

HINT:

If the warpage is more than the maximum, replace the cylinder head sub-assembly.

(b) Using a dye penetrant, check the intake ports, exhaust ports and cylinder head sub-assembly surface for cracks.

HINT:

If cracks are found, replace the cylinder head sub-assembly.

2. INSPECT INTAKE VALVE COMPRESSION SPRING

(a) Using a vernier caliper, measure the free length of the intake valve compression spring.

Standard Free Length:

58.81 mm (2.32 in.)

HINT:

If the free length is not as specified, replace the intake valve compression spring.

(b) Using a steel square, measure the deviation of the intake valve compression spring.

Maximum Deviation (Reference):

1.0 mm (0.0394 in.)

HINT:

If the deviation is more than the maximum, replace the intake valve compression spring.

*a

Deviation

*b

42.0 mm (1.65 in.)

3. INSPECT EXHAUST VALVE COMPRESSION SPRING

(a) Using a vernier caliper, measure the free length of the exhaust valve compression spring.

Standard Free Length:

61.08 mm (2.40 in.)

HINT:

If the free length is not as specified, replace the exhaust valve compression spring.

(b) Using a steel square, measure the deviation of the exhaust valve compression spring.

Maximum Deviation (Reference):

1.0 mm (0.0394 in.)

HINT:

If the deviation is more than the maximum, replace the exhaust valve compression spring.

*a

Deviation

*b

44.0 mm (1.73 in.)

4. INSPECT INTAKE VALVE

(a) Using a micrometer, measure the diameter of the intake valve stem.

Standard Valve Stem Diameter:

5.470 to 5.485 mm (0.215 to 0.216 in.)

HINT:

If the intake valve stem diameter is not as specified, check the intake valve guide bush oil clearance.

(b) Using a vernier caliper, measure the intake valve head margin thickness.

Standard Margin Thickness:

1.0 mm (0.0394 in.)

Minimum Margin Thickness:

0.5 mm (0.0197 in.)

HINT:

If the margin thickness is less than the minimum, replace the intake valve.

*a

Margin Thickness

(c) Using a vernier caliper, measure the overall length of the intake valve.

Standard Overall Length:

104.45 mm (4.11 in.)

Minimum Overall Length:

103.95 mm (4.09 in.)

HINT:

If the overall length is less than the minimum, replace the intake valve.

*a

Overall Length

5. INSPECT EXHAUST VALVE

(a) Using a micrometer, measure the diameter of the exhaust valve stem.

Standard Valve Stem Diameter:

5.465 to 5.480 mm (0.215 to 0.216 in.)

HINT:

If the exhaust valve stem diameter is not as specified, check the exhaust valve guide bush oil clearance.

(b) Using a vernier caliper, measure the exhaust valve head margin thickness.

Standard Margin Thickness:

1.0 mm (0.0394 in.)

Minimum Margin Thickness:

0.5 mm (0.0197 in.)

HINT:

If the margin thickness is less than the minimum, replace the exhaust valve.

*a

Margin Thickness

(c) Using a vernier caliper, measure the overall length of the exhaust valve.

Standard Overall Length:

108.7 mm (4.28 in.)

Minimum Overall Length:

108.2 mm (4.26 in.)

HINT:

If the overall length is less than the minimum, replace the exhaust valve.

*a

Overall Length

6. INSPECT VALVE GUIDE BUSH OIL CLEARANCE

(a) Using a caliper gauge, measure the inside diameter of the valve guide bush.

Standard Valve Guide Bush Inside Diameter:

5.51 to 5.53 mm (0.217 to 0.218 in.)

(b) Subtract the valve stem diameter measurement from the valve guide bush inside diameter measurement.

Standard Oil Clearance:

Item

Specified Condition

Intake Side

0.025 to 0.060 mm (0.000984 to 0.00236 in.)

Exhaust Side

0.030 to 0.065 mm (0.00118 to 0.00256 in.)

Maximum Oil Clearance:

Item

Specified Condition

Intake Side

0.080 mm (0.00315 in.)

Exhaust Side

0.10 mm (0.00394 in.)

HINT:

  • Oil clearance = Valve guide bush inside diameter - Valve stem diameter
  • If the oil clearance is more than the maximum, replace the valve and valve guide bush.

7. INSPECT INTAKE VALVE SEAT

(a) Apply a light coat of Prussian blue to the valve face.

(b) Lightly press the valve face against the intake valve seat.

NOTICE:

Do not rotate the valve while pressing it.

*a

Width

(c) Check the valve face and intake valve seat by using the following procedure:

(1) If Prussian blue appears 360° around the entire intake valve face, the valve face is concentric.

HINT:

If the valve face is not concentric, replace the intake valve.

(2) If Prussian blue appears 360° around the entire intake valve seat, the intake valve seat and valve face are concentric.

HINT:

If the valve face is not concentric, replace the cylinder head sub-assembly.

(3) Measure the width of the contact area of the intake valve seat and valve face.

Standard Width:

1.0 to 1.4 mm (0.0394 to 0.0551 in.)

8. INSPECT EXHAUST VALVE SEAT

(a) Apply a light coat of Prussian blue to the valve face.

(b) Lightly press the valve face against the exhaust valve seat.

NOTICE:

Do not rotate the valve while pressing it.

*a

Width

(c) Check the valve face and exhaust valve seat by using the following procedure:

(1) If Prussian blue appears 360° around the entire exhaust valve face, the valve face is concentric.

HINT:

If the valve face is not concentric, replace the exhaust valve.

(2) If Prussian blue appears 360° around the entire exhaust valve seat, the exhaust valve seat and valve face are concentric.

HINT:

If the valve face is not concentric, resurface the exhaust valve seat.

(3) Measure the width of the contact area of the exhaust valve seat and valve face.

Standard Width:

1.3 to 1.7 mm (0.0512 to 0.0669 in.)

9. INSPECT CAMSHAFT THRUST CLEARANCE

(a) Clean the No. 1 camshaft bearing cap, No. 2 camshaft bearing cap, 2 No. 3 camshaft bearing caps, No. 4 camshaft bearing cap, camshaft housing sub-assembly and camshaft journals.

(b) Place the camshaft and No. 2 camshaft on the camshaft housing sub-assembly on the cylinder head sub-assembly.

(c) Install the camshaft bearing caps.

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(d) Install the camshaft housing sub-assembly.

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(e) Using a dial indicator, measure the thrust clearance while moving the camshaft and No. 2 camshaft back and forth.

Standard Thrust Clearance:

Item

Specified Condition

Camshaft

0.04 to 0.17 mm (0.00157 to 0.00669 in.)

No. 2 Camshaft

0.04 to 0.17 mm (0.00157 to 0.00669 in.)

Maximum Thrust Clearance:

Item

Specified Condition

Camshaft

0.22 mm (0.00866 in.)

No. 2 Camshaft

0.22 mm (0.00866 in.)

HINT:

If the thrust clearance is more than the maximum, replace the camshaft housing sub-assembly. If the thrust surface is damaged, replace the camshaft.