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Eliminate head gasket failures on Cat diesels
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.
Q. What’s the best way to install sleeves in oversize Mercedes cylinders?
A. The following information pertains to installation of aluminum sleeves in 1984-’99 Mercedes-Benz 4.2L and 5.0L, 116, 117 and 119 engines. This aluminum engine block requires a special honing procedure for the aluminum bores. This procedure should be considered any time cylinder hole service is required.
Mercedes-Benz offers an aluminum cylinder sleeve to repair cylinder bores. These sleeves should only be installed and machined/ honed by shops that are capable of carrying out this kind of work to Mercedes-Benz specifications.
Below is a list of the machining dimensions necessary to install new sleeves in these engines. After the sleeves are installed they can be finished to fit either standard or +.5 mm oversize pistons.
For Mercedes Block
Basic Bore for Aluminum Sleeve
Basic Bore for Sleeve Collar
Counterbore Depth for Sleeve