Cylinder Head Bolt Torque and Sequence

Cylinder Head
Engine Mechanical





Check that the nominal length of each cylinder head bolt meets the limit. If it exceeds the limit, replace the bolt with a new one.
Limit (A) 99.4 mm (3.91 inches)
Apply a small amount of engine oil to the thread of the bolts and to the washers.
Use special tool MB991654 to tighten the cylinder head bolts in the following procedures.





Tighten the bolts to 78 ± 2 Nm (58 ± 1 ft. lbs.) in the order shown.
Loosen the bolts fully in the reverse sequence of that shown.
Tighten the bolts to 20 ± 2 Nm (15 ± 1 ft. lbs.) in the order shown.
Reconfirm all bolts tightened firmly.





Apply a paint mark to the heads of the cylinder head bolts and cylinder head, then tighten 90 degrees as shown.

CAUTION:
^ The bolt is not tightening sufficiently if the tightening angle is less than 90 degrees.
^ If the tightening angle exceeds the standard specification, remove the bolt and start over from step 1.

Tighten 90 degrees as shown, then check to see that the paint mark on the head of the cylinder head bolt and the paint mark on the cylinder head are aligned.











Using special tool MB991654 tighten the bolts to the specified torque, using the tightening sequence shown.
Tightening torque 78 ± 2 Nm (58 ± 2 ft. lbs.)
Loosen all bolts fully in the reverse order of tightening.
Retighten the loosened bolts to the specified torque in the tightening sequence shown.
Tightening torque 20 ± 2 Nm (15 ± 1 ft. lbs.)





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

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.