Using special tool Cylinder head bolt wrench (MB991654), loosen the cylinder head bolts. Loosen each bolt evenly, little by little, by two or three steps.

1. Set special tool Valve spring compressor (MD998735) as illustrated to compress the valve spring. Remove the retainer lock.

2. Relieve the spring tension and remove the valve, retainer, spring, etc. Store removed valves, springs, and other parts, tagged to indicate their cylinder number and location for assembly.

 CAUTION
The special tool must be used to install the valve stem seal. Improper installation could result in oil leaking past the valve guide.

1. Install the valve spring seat.

2. Using special tool Valve stem seal installer (MD998737), install a new valve stem seal.

Install the valve spring with its identification color painted end (larger pitch side) upward (toward the valve spring retainer).

 CAUTION
Do not compress the valve spring excessively. It can damage the stem seal.

1. Set special tool Valve spring compressor (MD998735) as illustrated to compress the valve spring. Install the retainer locks.

2. Relieve the spring tension. Check that the retainer locks are seated correctly.

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

2. Apply engine oil to the thread of the bolts and to the washers.

3. Using special tool Cylinder head bolt wrench (MB991654) tighten the bolts to the specified torque, using the tightening sequence shown.
Tightening torque: 78 ± 2 N·m

4. Loosen all bolts fully in the reverse order of tightening.

5. Retighten the loosened bolts to in the tightening sequence shown.
Tightening torque: 20 ± 2 N·m

6. Make a paint mark across each bolt head and cylinder head.

7. Tighten the cylinder head bolts 90 degrees in the specified order.

 CAUTION
• If the bolt is turned less than 90 degrees, proper fastening performance may not be achieved. Be careful to turn each bolt exactly 90 degrees.
• If the bolt is overtightened, loosen the bolt completely and then retighten it by repeating the tightening procedure from step 1.
8. Tighten the bolts another 90 degrees 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.