Lexus LS400 (2000 year). Service manual — part 91

A03208

A03209

A03201

12.3 – 12.7 mm

EM–52

–

ENGINE MECHANICAL

CYLINDER HEAD

1234

If the thrust clearance is greater than maximum, replace the
camshaft. If necessary, replace the bearing caps and cylinder
head as a set.
(d)

Remove the camshafts.

(e)

Remove the camshaft timing tube.

22.

INSPECT CAMSHAFT GEAR BACKLASH

(a)

Install the camshaft timing tube. (See page

EM–58

)

(b)

Install the camshafts without installing the exhaust cam
sub–gear and front bearing cap. (See page

EM–58

)

(c)

Using a dial indicator, measure the backlash.
Backlash:

Standard

0.020 – 0.200 mm (0.0008 – 0.0079 in.)

Maximum

0.30 mm (0.0188 in.)

If the backlash is greater then maximum, replace the cam-
shafts.
(d)

Remove the camshafts.

23.

INSPECT VALVE LIFTERS AND LIFTER BORES

(a)

Using a caliper gauge, measure the lifter bore diameter
of the cylinder head.
Lifter bore diameter:
31.000 – 31.016 mm (1.2205 – 1.2211 in.)

(b)

Using a micrometer, measure the lifter diameter at the
valve lifter center line, 12.3 – 12.7 mm (0.484 – 0.500 in.)
from the valve lifter head.
Lifter diameter:
30.966 – 30.976 mm (1.2191 – 1.2195 in.)

(c)

Subtract the lifter diameter measurement from the lifter
bore diameter measurement.
Standard oil clearance:

Standard

0.024 – 0.050 mm (0.0009 – 0.0020 in.)

Maximum

0.07 mm (0.0028 in.)

If the oil clearance is greater than maximum, replace the lifter.
If necessary, replace the cylinder head.

A02881

A02882

Upper Intake Manifold Side

Cylinder Head Side

P21864

A02825

Measuring Point

2.5 mm
(0.98 in.)

–

ENGINE MECHANICAL

CYLINDER HEAD

EM–53

1235

24.

INSPECT INTAKE MANIFOLD

(a)

Upper intake manifold:
Using a precision straight edge and feeler gauge, mea-
sure the surface contacting the lower intake manifold for
warpage.
Maximum warpage: 0.15 mm (0.0059 in.)

If warpage is greater than maximum, replace the upper intake
manifold.

(b)

Lower intake manifold:
Using a precision straight edge and feeler gauge, mea-
sure the surface contacting the cylinder head and upper
intake manifold for warpage.
Maximum warpage: 0.15 mm (0.0059 in.)

If warpage is greater than maximum, replace the lower intake
manifold.

25.

INSPECT EXHAUST MANIFOLD

Using a precision straight edge and feeler gauge, measure the
surface contacting the cylinder head for warpage.

Maximum warpage: 0.50 mm (0.0197 in.)

If warpage is greater than maximum, replace the manifold.

26.

INSPECT CYLINDER HEAD BOLTS

Using vernier calipers, measure the thread outside diameter of
the bolt.

Outside diameter:

Standard

9.770 – 9.960 mm (0.3846 – 0.3921 in.)

Minimum

9.60 mm (0.3780 in.)

If the diameter is less than minimum, replace the bolt.

EM09T–02

A03195

80–100

°

C

A03196

SST

A03197

Use STD

Bushing size

10.285 – 10.306

Bushing bore diameter

Both intake and exhaust

(0.4049 – 0.4057)

Use O/S STD

mm (in.)

(0.4069 – 0.4077)

10.335 – 10.356

P21844

34.5 mm
(1.358 in.)

40.5 mm
(1.594 in.)

Intake

Exhaust

EM–54

–

ENGINE MECHANICAL

CYLINDER HEAD

1236

REPLACEMENT

1.

REPLACE VALVE GUIDE BUSHINGS

(a)

Gradually heat the cylinder head to 80 – 100

°

C (176 –

212

°

F).

(b)

Using SST and a hammer, tap out the guide bushing.
SST

09201–01055, 09950–70010 (09951–07100)

(c)

Using a caliper gauge, measure the bushing bore diame-
ter of the cylinder head.

(d)

Select a new guide bushing (STD or O/S 0.05).

If the bushing bore diameter of the cylinder head is greater than
10.306 mm (0.4057 in.), machine the bushing bore to the fol-
lowing dimension:

10.335 – 10.356 mm (0.4069 – 0.4077 in.)

If the bushing bore diameter of the cylinder head is greater than
10.356 mm (0.4077 in.), replace the cylinder head.

HINT:
Different the bushings are used for the intake and exhaust.

A03198

SST

A03199

A03200

Sharp 5.5 mm Reamer

A04107

Bend

Claw

Pry

A04108

Down Ward

Claw

SST

Return

SST

–

ENGINE MECHANICAL

CYLINDER HEAD

EM–55

1237

(e)

Gradually heat the cylinder head to 80 – 100

°

C (176 –

212

°

F).

(f)

Using SST and a hammer, tap in a new guide bushing to
the specified protrusion height.
Protrusion height:

Intake

9.2 – 9.8 mm (0.362 – 0.386 in.)

Exhaust

8.2 – 8.8 mm (0.323 – 0.346 in.)

SST

09201–01055, 09950–70010 (09951–07100)

(g)

Using a sharp 5.5 mm reamer, ream the guide bushing
to obtain the standard specified clearance (See page

EM–44

) between the guide bushing and valve stem.

2.

REPLACE SPARK PLUG TUBE GASKETS

(a)

Bend the 4 ventilation case claw installed on the cylinder
head cover to an angle of 90

°

or more.

(b)

Using a screwdriver, pry out the gasket.

NOTICE:
Be careful not to damage the cylinder head cover, Tape the
screwdrive tip.

(c)

Using SST and a hammer, tap in a new gasket until its sur-
face is flush with the upper edge of the cylinder head cov-
er.
SST

09950–60010 (09551–00240, 09951–00440,
09952–06010), 09950–70010 (09951–07100)

NOTICE:
Be careful of the installation direction.
(d)

Apply a light coat of MP grease to the gasket lip.

(e)

Return the ventilation case claw to its original position.