I have a 04 with 280,*** miles and fought the same thing. Clean what you can take your push rods out and spray carb clean through the holes should help with your noise. At times i also drop my filter and add a quart of ATF to my oil because of the detergent in it helps to clean the engine wouldnt run a lot of miles like that maybe 500 so do it right before a oil change. Flush engine from time to time as well. Thats what i got for you my man good luck.

 

My 06 5.3 has 304k miles and no engine sludge. Sludge is caused mainly by water in the oil. Are you losing any coolant? Sometimes the leak is internal so you wont see any puddles or drips under the truck or you wont smell it on hot engine parts. A cracked head gasket is usually the cause of water in the oil.

 

Have you noticed coolant loss? That will sludge up an engine fast.

Subject:Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found #06-06-01-019B - (06/12/2007)

Models:2004-2006 Buick Rainier
2001-2006 Cadillac Escalade Models
2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models
2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models
2001-2004 Oldsmobile Bravada
2005-2006 Saab 9-7X
with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z -- RPOs LR4, LM7, LH6, L33, L59)

This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).

Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.

Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.

Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

If the cylinder head(s) is a Castech casting (1), inspect the area around the five oil drain holes for witness marks indicating coolant seepage over time (2).

Important: If No evidence of coolant loss is found on inspection of Castech casting cylinder head(s), follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

The crack location can be found in any of the five cylinder head(s) oil drains. This can be seen as a clean or shiny area, on an otherwise stained surface (1). Pressurizing the cooling system at this time may reveal coolant, air, or a combination, weeping in the described area. If inspection reveals evidence of coolant witness marks (1), replace the entire cylinder head(s) assembly.

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