Cylinder Head and Valves
CYLINDER HEAD AND VALVESREMOVAL AND INSTALLATION
Removal Steps 1-20 & Required Special Tools:
REMOVAL SERVICE POINTS
[[A]] CYLINDER HEAD BOLT REMOVAL
Using the special tool MB991653 to loosen the cylinder head bolts.
[[B]] RETAINER LOCK REMOVAL
1. Using special tool MD998735 or MD998772, compress the retainer locks.
2. Remove the retainer locks.
NOTE: Tag removed valves, springs and other components, noting their cylinder numbers and locations to facilitate reassembly. Store these components safely.
[[C]] VALVE STEM SEAL REMOVAL
Do not reuse removed valve stem seal.
[[D]] VALVE HANDLING PRECAUTIONS
WARNING: Sodium reacts violently with water or moisture generation heat and liberating hydrogen. It must be handled with utmost care because otherwise the following dangerous conditions may result:
^ Loss of eyesight if sodium gets in eyes.
^ Burns if sodium contact skin.
^ Fire hazard.
1. Handling of Sodium-filled Exhaust Valves
1. Sodium-filled exhaust valves are not dangerous and may be handled in the same way as ordinary valves unless they are broken.
2. Never try to break the valves and expose sodium to the air.
3. When worn exhaust valves are to be discarded, have them disposed of by a salvage company equipped with special disposal system, notifying them that the valves contain sodium.
4. Should the exhaust valves be broken, neutralize sodium using the method described below, and discard the valves in the same way as ordinary valves.
CAUTION:
^ Do not let the solution contact the eyes or the skin.
^ Should it get in the eyes, immediately flush them with clean water thoroughly, and receive medical attention. When it contacts he skin, wash with ample amounts of clean water.
2. How to Neutralize Sodium
1. Place a container filled with more than 10 liters (10.6 qt) of water in a well ventilated large space.
2. Wear rubber gloves and goggles, and carefully take out broken valves from the cylinder head.
CAUTION:
^ Valves must be neutralized one at a time.
^ Put a valve in the container only after sodium in the preceding one has completely reacted with water.
3. Put a broken valves in the water-filled container and quickly get away from the container at least 2 or 3 m (6.6 or 9.8 ft).
4. Keep fire away from the container during the neutralization. The resulting hydrogen gas is highly explosive.
NOTE: The reaction occurs when water enters the cavity in he valve. Hydrogen gas may be trapped inside the valve, temporarily blocking the water passage. In such a case, wait until hydrogen gas in released and remaining sodium reacts with water.
5. After the neutralization of sodium, water in the container contains sodium hydroxide and is highly alkaline. The water solution should be disposed of according to local regulations.
INSTALLATION SERVICE POINTS
]]A[[ VALVE STEM SEAL INSTALLATION
CAUTION:
^ Do not reuse removed valve stem seals.
1. Install the valve spring seat.
NOTE: Do not confuse the stem seals for intake valves with those for exhaust valves.
CAUTION:
^ The valve stem seal must be installed using the correct special tool. Incorrect installation could result in oil leaking past the valve guide.
2. Using special tool MD998737, install a new stem seal to the valve guide.
]]B[[ VALVE SPRING INSTALLATION
Install the valve spring so that the painted end is on the rocker arm side.
]]C[[ RETAINER LOCK INSTALLATION
Using special tool MD998735 or MD998772, compress the valve spring and insert the retainer lock into position.
NOTE: The valve spring, if excessively compressed, causes the bottom end of retainer to be in contact with the stem seal, and damage it.
]]D[[ CYLINDER HEAD BOLT INSTALLATION
1. When the removed cylinder head bolts are to be reused, check that the shank length of each bolt meets the limit. If it exceeds the limit, replace the bolts.
Limit: 99.4 mm (3.91 inches)
2. Apply engine oil to the thread of the bolts and to the washers.
3. Using special tool MB991654 tighten the bolts to the specified torque 78 ± 2 Nm (58 ± 1 ft. lbs.), using the tightening sequence shown.
4. Loosen all bolts fully in the reverse order of tightening.
5. Retighten the loosened bolts to 20 ± 2 Nm (15 ± 1 ft. lbs.) in the tightening sequence shown.
CAUTION:
^ If the bolt is turned less than 90 degree angle, proper fastening performance may not be achieved. Be careful to turn each bolt exactly 90 degree angle.
^ If the bolt is overtightened, loosen the bolt completely and then retighten it by repeating the tightening procedure from step 1.
6. Make a paint mark across each bolt head and cylinder head.
7. Tighten the cylinder head bolts 90 degree angle in the specified order.
8. Tighten the bolts another 90 degree angle in the same order as in step 7, and check that the paint marks on the cylinder head bolt are aligned with the paint marks on the cylinder head.
INSPECTION
CYLINDER HEAD
1. Before cleaning the cylinder head, check it for water leaks, gas leaks, cracks, and other damage.
2. Remove all oil, water scale, sealant, and carbon. After cleaning the oil passages, blow air through them to verify that they are not blocked.
3. Check the cylinder head gasket surface for flatness by using a straight edge and feeler gauge.
Standard value: 0.05 mm (0.0020 inch)
Limit: 0.2 mm (0.008 inch)
4. If flatness exceeds the specified limit, grind the gasket surface to specification.
Grinding limit: *0.2 mm (0.008 inch)
*Includes/combined with cylinder block grinding
Cylinder head height (Specification when new): 131.9 - 132.1 mm (5.193 - 5.201 inches)
VALVE
1. Check the valve face for correct contact. If contact is uneven or incomplete, reface the valve seat.
2. If the margin is less than specified, replace the valve.
Standard value:
Intake: 1.0 mm (0.039 inch)
Exhaust: 1.5 mm (0.059 inch)
Limit:
Intake: 0.5 mm (0.020 inch)
Exhaust: 1.0 mm (0.039 inch)
3. Measure the valve length. If the measurement is less than specified, replace the valve.
Standard value:
Intake: 109.50 mm (4.311 inches)
Exhaust: 109.70 mm (4.319 inches)
Limit:
Intake: 109.00 mm (4.291 inches)
Exhaust: 109.20 mm (4.299 inches)
VALVE SPRING
1. Measure the valve spring free height. If the measurement is less than specified, replace the spring.
Standard value: 50.4 mm (1.98 inches)
Limit: 49.4 mm (1.94 inches)
2. Measure the squareness of the spring. If the measurement is less than specified, replace the spring.
Standard value: 2° or less
Limit: 4°
VALVE GUIDE
Measure the clearance between the valve guide and valve stem. If the clearance exceeds the specified limit, replace the valve guide or valve, or both.
Standard value:
Intake: 0.02 - 0.05 mm (0.0008 - 0.0020 inch)
Exhaust: 0.05 - 0.09 mm (0.0020 - 0.0035 inch)
Limit:
Intake: 0.10 mm (0.0039 inch)
Exhaust: 0.15 mm (0.0059 inch)
VALVE SEAT
Assemble the valve, then measure the valve stem projection between the end of the valve stem and the spring seating surface. If the measurement exceeds the specified limit, replace the valve seat.
Standard value:
Intake: 49.20 mm (1.9370 inches)
Exhaust: 48.40 mm (1.9055 inches)
Limit
Intake: 49.70 mm (1.9567 inches)
Exhaust: 48.90 mm (1.9252 inches)
VALVE SEAT RECONDITIONING PROCEDURE
1. Before correcting the valve seat, check the clearance between the valve guide and valve. If necessary, replace the valve guide.
2. Using the appropriate special tool or seat grinder, correct the valve seat to achieve the specified seat width and angle.
3. After correcting the valve seat, lap the valve and valve seat using lapping compound. Then, check the valve stem projection.
VALVE SEAT REPLACEMENT PROCEDURE
1. Cut the valve seat to be replaced from the inside to reduce the wall thickness. Then, remove the valve seat.
2. Rebore the valve seat hole in the cylinder head to match the selected oversize valve seat diameter.
Intake valve seat hole diameter
0.3 oversize: 35.30 - 35.33 mm (1.3898 - 1.3909 inches)
0.6 oversize: 35.60 - 35.63 mm (1.4016 - 1.4028 inches)
Exhaust valve seat hole diameter
0.3 oversize: 33.30 - 33.33 mm (1.3110 - 1.3122 inches)
0.6 oversize: 33.60 - 33.63 mm (1.3228 - 1.3240 inches)
3. Prevent galling of the cylinder head bore by cooling the valve seat with liquid nitrogen before press-fitting it.
4. Correct the valve seat to achieve the specified width and angle.
VALVE GUIDE REPLACEMENT PROCEDURE
1. Using a press, push the valve guide out toward the cylinder block side.
2. Rebore the valve guide hole in the cylinder head to match the oversize valve guide that is to be fitted.
CAUTION: Do not install a valve guide of the same size again.
Valve guide hole diameters in cylinder head
0.05 oversize: 12.05 - 12.07 mm (0.4744 - 0.4751 inch)
0.25 oversize: 12.25 - 12.27 mm (0.4823 - 0.4831 inch)
0.50 oversize: 12.50 - 12.52 mm (0.4921 - 0.4929 inch)
3. Press-fit the valve guide until it projects by the specified amount.
Standard value: 19.5 mm (0.768 inch)
CAUTION:
^ The valve guide must be installed from the upper side of the cylinder head.
^ The valve guides differ in length on the intake and exhaust sides.
Valve guide length
Intake: 45.5 mm (1.791 inches)
Exhaust: 50.5 mm (1.988 inches)
4. After press-fitting the valve guide, insert a new valve and check that it slides smoothly.