Isuzu N-Series. Manual - part 491

Engine Mechanical (4HK1-TC)   6A-69

Valve Stem Seal and Valve Spring

Component

Legend

1. Camshaft Bearing Cap
2. Camshaft Bearing
3. Camshaft Assembly
4. Rocker Arm Shaft Assembly
5. Valve Stem Oil Seal

6. Valve Spring
7. Spring Upper Seat
8. Split Collar
9. Bridge

 

Removal

1. Remove the cylinder head cover.

Refer to “Cylinder Head Cover”.

2. Remove the rocker arm shaft assembly.

Refer to “Rocker Arm Shaft Assembly”.

3. Remove the camshaft assembly.

Refer to “Camshaft Assembly”.

4. Remove the bridge cap (1).

5. Remove the bridge (2).

Caution:
Keep the removed bridge and bridge cap properly so
that they may be put back to the original position.

N6A6112E

6A-70   Engine Mechanical (4HK1-TC)

Legend

1. Bridge Cap
2. Bridge

 

Caution:
Pay full attention so as not to drop the bridge cap in the
gear case of the rear part of the cylinder head or a hole
into which oil pours back in the front.

6. Remove the split collar.

• Apply compressed air over the cylinder from a

glow plug hole to keep the valve at the home
position.

• Use a replacer to compress the valve spring to

remove the split collar.

Special tool
Valve spring replacer: 5-8840-2621-0 (J-43263)
Pivot: 5-8840-2808-0 (EN-46721)

7. Remove the spring upper seat.

• Remove the special tool to remove the upper

seat.

8. Remove the valve spring.

Put the removed valve springs in order by cylinder
number.

9. Remove the valve stem oil seal.

• Use pliers to remove the oil seal.

Caution:
Do not use the removed oil seal again.

Inspection

Inspect the valve spring
Caution:
Check the valve spring visually and if there is clear
damage or wear-out, replace it.

1. Free length

• Measure free length of the spring and if it is

shorter than the prescribed limit, replace the
spring.

N6A6093E

N6A6113E

Free length of the valve spring 

mm (in)

Inlet

Exhaust

Standard

59.9 (2.36)

70.3 (2.76)

Limit

56.9 (2.24)

67.3 (2.65)

N6A6114E

Engine Mechanical (4HK1-TC)   6A-71

2. Valve spring squareness

• Use a surface plate and a square to measure

the valve spring squareness.
If the measured value exceeds the specified
limit, replace the valve spring.

3. Tension

• Use a spring tester to compress the spring to

the installation height. Measure tension of the
compressed spring. If the measurement is
lower than the limit, replace the spring.

Installation

1. Install the valve stem oil seal.

• Apply engine oil over the peripheral part of the

valve guide and install the oil seal by using a
valve stem seal installer.

Caution:
After installing the valve stem oil seal, check if it is
inserted deeply enough and the oil seal is not tilted or
the garter spring has not come off.

Valve spring squareness

mm (in)

Limit

1.0 (0.04)

N6A6115E

N6A6116E

Tension of the valve spring 

Inlet

Exhaust

Installation 

length mm (in)

47.0 (1.85)

47.0 (1.85)

Standard N (lb)

333 (74.9)

490 (110.2)

Limit N (lb)

315 (71.0)

463 (104.3)

N6A6117E

6A-72   Engine Mechanical (4HK1-TC)

Special tool
Valve stem seal installer: 5-8840-2833-0 
(EN-47685)

2. Install the valve spring.

• Install it with the paint mark or the narrow side

of the spring pitch being the lower side (cylinder
head side).

Legend

1. Spring Pitch
2. Paint Mark

 

3. Install the spring upper seat.
4. Install the split collar.

• Apply compressed air over the cylinder from the

glow plug holes to keep the valve at the home
position.

• Use a replacer to compress the valve spring

and install the split collar.

Special tool
Valve spring replacer: 5-8840-2621-0 (J-43263)
Pivot: 5-8840-2808-0 (EN-46721)

5. Apply engine oil over the bridge and install it.

Caution:
Move it up and down to check if them moves smoothly.

6. Apply engine oil over the bridge cap and install it.

Caution:
Pay full attention so as not to drop the bridge cap in the
gear case of the rear part of the cylinder head or the
hole into which oil pours back in the front.

Paint mark

Inlet

Blue

Exhaust

Red

N6A6118E

N6A6119E

N6A6113E