Lexus GS300/400 (2000 year). Service manual — part 137

EM0DC–03

A02682

A02683

A02705

A02706

P02072

EM–40

–

ENGINE MECHANICAL (2JZ–GE)

CYLINDER HEAD

1394

INSPECTION

1.

CLEAN TOP SURFACES OF PISTONS AND
CYLINDER BLOCK

(a)

Turn the crankshaft, and bring each piston to top dead
center (TDC). Using a gasket scraper, remove all the car-
bon from the piston top surface.

(b)

Using a gasket scraper, remove all the gasket material
from the top surface 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 HEAD

(a)

Remove the 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 contact sur-
face.

(b)

Clean the combustion chambers.
Using a wire brush, remove all the carbon from the com-
bustion chambers.

NOTICE:
Be careful not to scratch the cylinder block contact sur-
face.

(c)

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

A02707

A02711
P02145

P02135

P02144

A03796

A02708

EM0580

–

ENGINE MECHANICAL (2JZ–GE)

CYLINDER HEAD

EM–41

1395

(d)

Clean the cylinder head.
Using a soft brush and solvent, thoroughly clean the cylin-
der head.

3.

INSPECT CYLINDER HEAD

(a)

Inspect for the flatness.
Using precision straight edge and feeler gauge, measure
the surfaces contacting the cylinder block, intake and ex-
haust manifolds for warpage.
Maximum warpage: 0.10 mm (0.0039 in.)

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

(b)

Inspect for the cranks.
Using a dye penetrant, check the combustion chamber,
intake ports, exhaust ports and cylinder block surface for
cracks.

If cracked, replace the cylinder head.

4.

CLEAN VALVES

(a)

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

(b)

Using a wire brush, thoroughly clean the valve.

Z02413

Z00052

Z00054

44.5

°

EM0181

Margin Thickness

EM–42

–

ENGINE MECHANICAL (2JZ–GE)

CYLINDER HEAD

1396

5.

INSPECT VALVE STEMS AND GUIDE BUSHINGS

(a)

Using a caliper gauge, measure the inside diameter of the
guide bushing.
Bushing inside diameter:
6.010 – 6.030 mm (0.2366 – 0.2374 in.)

(b)

Using a micrometer, measure the diameter of the valve
stem.
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 valve stem diameter measurement from the
guide bushing inside diameter measurement.
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. (See page

EM–48

)

6.

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:
0.8 – 1.2 mm (0.031 – 0.047 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

A02709

45

°

Carbide Cutter

Z00373

Width

P03966

Width

45

°

15

°

–

ENGINE MECHANICAL (2JZ–GE)

CYLINDER HEAD

EM–43

1397

(d)

Check the valve overall length.
Standard overall length:

Intake

98.29 – 98.79 mm (3.8697 – 3.8894 in.)

Exhaust

98.84 – 99.34 mm (3.8913 – 3.9110 in.)

Minimum overall length:

Intake

98.19 mm (3.8657 in.)

Exhaust

98.74 mm (3.8874 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 the minimum overall length.

7.

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 thin coat of Prussian blue (or white lead) to the
valve face. Lightly press the valve against the seat. Do not
rotate the valve.

(c)

Check the valve face and seat for the following:

If blue appears 360

°

around the face, the valve is

concentric. If not, replace the valve.

If blue appears 360

°

around the valve seat, the

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

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

If not, correct the valve seats as follows:

Intake

1.0 – 1.4 mm (0.039 – 0.055 in.)

Exhaust

1.2 – 1.6 mm (0.047 – 0.063 in.)

(1)

If the seating is too high on the valve face, use 15

°

and 45

°

cutters to correct the seat.