Duramax LLY – CYLINDER BLOCK SERVICE – Inspection

Check all of the block surfaces for nicks, scratches, cracks, damaged threads, or evidence of porosity at any point. Minor nicks and scratches can be smoothed with a fine tooth file or 180 grit emery. Damaged threads can be either chased, or repaired with Helicoil stainless steel thread inserts. Replace the block if cracked, or if porous spots are evident.

Light discoloration of gasket surfaces and cylinder bores is normal and not a cause for replacement. However, evidence of severe overheating and heat checking will require closer attention to dimensional checks.

Check condition of the expansion plugs (Figure 2-102), and camshaft plug. Replace the plugs if corroded, rusted, loose, or coolant leakage is evident. Refer to the procedure in this section if plug replacement is required.

Check the cam bearings. Locations in the block are shown (Figure 2-100).

It is not necessary to replace the bearings if they only have a burnished, or polished appearance, and wear is very minimal. However, replace all of the bearings if one or more are scored, flaking, distorted, etched, pitted, loose, or misaligned. Also replace the bearings if the block was hot tank cleaned with the bearings in place. Refer to the bearing replacement procedure in this section.

On turbocharged engines, check the oil feed holes at the rear of the block near the oil pump drive. Make sure the feed holes are clear and not plugged. This is important as any restrictions will result in turbocharger failure.

Remove and inspect the oil pressure regulator and safety valves. Replace the regulator valve plug; do not reuse it. Replace the two valves if seized, binding, or plugged. Do not try to salvage the valves.

Check the pipe plugs at the sides and front of the block (Figure 2-103). Replace any plugs that are loose or leaking. Coat replacement plug threads with Permatex #2, or high temp silicone sealant before installation.

 

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