Q. To eliminate head gasket failures on Cat diesels, how should the heads be torqued?
A. Pressurizing the cooling system with the oil pan removed can differentiate between a water pump leak and a cylinder head gasket leak before removing the head. If a head gasket is the source of the problem this revised cylinder head torque procedure can eliminate repeat head gasket failures on Caterpillar C10 and C12 diesel engines.
- Replace all cylinder head bolts with p/n 129-3184, reduced shank bolts. (Jake engines use stud p/n 132-3229). Failure to replace bolts that have corrosion damage may lead to (premature) breakage.
- Using a straight edge and feeler gauge, check cylinder head/block deck surface for warpage. Surface flatness specs are: .002˝ per 6˝ or .006˝ overall. If either block or head surface is out of spec, replace or resurface.
- Use an M16 X 2 (8T-3096) bottoming tap to clean the 26 bolt holes in the block to allow the head bolts to produce the correct clamping load.
- If threads in the cylinder block are damaged, Caterpillar recommends a Heli-coil® insert (p/n 1084-16CN-32) for these engines.
- Use only the revised reduced wrap fire ring head gaskets. Serial numbers prior to 2KS00388, 9NS16228, 8YS05399 and 3CS00718 (or if the engine has a combination of scalloped and straight cylinder block or head) use p/n 187-3306. Engines after that serial number use p/n 187-3307.
- When tightening the head bolts, to obtain the proper head gasket loading and more uniform higher average clamping load of the bolts, use this torque procedure and the sequence illustrated in Figure 1.
- Lubricate all bolt threads, underside of head bolt and washer with 6V-4876 molycoat paste or aftermarket equivalent.
- Tighten bolts 1-26 in proper sequence to 120 ft.lbs.
- Tighten bolts 1-26 again in sequence to 120 ft.lbs.
- Rotate each bolt in sequence an additional 90 degrees.
- Loosen all bolts (washers should be loose under bolts).
- Repeat steps 2, 3, 4.
- Tighten bolts 27-33 in proper sequence to 20 ft.lbs.
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