Lexus RX300 (MCU15). Manual - part 440

P12755

A05231

A05227

EM0580

EM–44

–

ENGINE MECHANICAL

CYLINDER HEAD

LEXUS RX300   (RM785E)

5.

CLEAN VALVE GUIDE BUSHINGS

Using a valve guide bushing brush and solvent, clean all the
guide bushings.

6.

INSPECT FOR FLATNESS

Using a precision straight edge and feeler gauge, measure the
surfaces contacting the cylinder block and the manifolds for
warpage.

Maximum warpage: 0.10 mm (0.0039 in.)

If warpage is greater than maximum, replace the cylinder head.

7.

INSPECT FOR CRACKS

Using a dye penetrant, check the combustion chamber, intake
ports, exhaust ports and cylinder block surface for cracks.
If cracked, replace the cylinder head.

8.

CLEAN VALVES

(a)

Using a gasket scraper, chip off any carbon from the valve
head.

(b)

Using a wire brush, thoroughly clean the valve.

P12754

Z00052

Z00054

44.5

°

EM0181

Margin Thickness

–

ENGINE MECHANICAL

CYLINDER HEAD

EM–45

LEXUS RX300   (RM785E)

9.

INSPECT VALVE STEMS AND GUIDE BUSHINGS

(a)

Using a caliper gauge, measure the inside diameter of the
guide bushing.
Bushing inside diameter:
5.510 – 5.530 mm (0.2169 – 0.2177 in.)

(b)

Using a micrometer, measure the diameter of the valve
stem.
Valve stem diameter: 
Intake: 5.470 – 5.485 mm (0.2154 – 0.2159 in.) 
Exhaust: 5.465 – 5.480 mm (0.2152 – 0.2157 in.)

(c)

Subtract the valve stem diameter measurement from the
guide bushing guide bushing inside diameter measure-
ment.
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.

10.

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 face
angle.
Valve face angle: 44.5°

(c)

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 margin thickness is less than minimum, replace the valve.

EM2534

Overall Length

EM0255

A05228

P12729

Width

Z03988

1.0 – 1.4 mm

45

°

30

°

EM–46

–

ENGINE MECHANICAL

CYLINDER HEAD

LEXUS RX300   (RM785E)

(d)

Check the valve overall length.
Standard overall length: 
Intake: 95.45 mm (3.5779 in.) 
Exhaust: 95.40 mm (3.7559 in.)
Minimum overall length: 
Intake: 94.95 mm (3.7382 in.) 
Exhaust: 94.90 mm (3.7362 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 minimum.

11.

INSPECT AND CLEAN VALVE SEATS

(a)

Using a 45

° carbide cutter, resurface the valve seats. 

Remove only enough metal to clean the seats.

(b)

Check the valve seating position. 
Apply a light coat of prussian blue (or white lead) to the
valve face. Lightly press the valve against the seat. Do not
rotate valve.

(c)

Check the valve face and seat for the following:

S

If blue appears 360

° around the face, the valve is

concentric. If not, replace the valve.

S

If blue appears 360

° around the valve seat, the

guide and face are concentric. If not, resurface the
seat.

S

Check that the seat contact is in the middle of the
valve face with the following width:

1.0 – 1.4 mm (0.039 – 0.055 in.)

If not, correct the valve seats as follows:

S

If the seating is too high on the valve face, use 30

°

and 45

° cutters to correct the seat.

Z03989

1.0 – 1.4 mm

75

°

45

°

A05229

EM0988

Deviation

EM0801

EM0281

–

ENGINE MECHANICAL

CYLINDER HEAD

EM–47

LEXUS RX300   (RM785E)

S

If the seating is too low on the valve face, use 75

°

and 45

° cutters to correct the seat.

(d)

Hand–lap the valve and valve seat with an abrasive com-
pound.

(e)

After hand–lapping, clean the valve and valve seat.

12.

INSPECT VALVE SPRINGS

(a)

Using a steel square, measure the deviation of the valve
spring.
Maximum deviation: 2.0 mm (0.079 in.)

If the deviation is greater than maximum, replace the valve
spring.

(b)

Using vernier calipers, measure the free length of the
valve spring.
Free length: 45.50 mm (1.7913 in.)

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

(c)

Using a spring tester, measure the tension of the valve
spring at the specified installed length.
Installed tension: 
186 – 206 N (19.0 – 21.0 kgf, 41.9 – 46.3 lbf) 
at 33.8 mm (1.331 in.)

If the installed tension is not as specified, replace the valve
spring.