The intake gaskets went through several design changes to correct a coolant and oil mixing for the last ten years. Sludge in the coolant may be a symptom of this but is extremely rare.
The intake manifold gaskets leak coolant into the valley between the cylinder heads causing the most common symptom of coolant mixing in with the oil in the crankcase, not the radiator.
The sludge buildup in your system is caued by the original coolant engineered by GM called Dex Cool that was found to be caustic to several things in the engine. You guessed it, one was intake gaskets. But back to the side effect, after sitting for few years the Dex Cool coagultes like and becomes that brown color in you radiator. GM even settled with the public last year to pay or reimburse part of the cost for these repairs. Unfortunately the settlement ended October 27, 2008.
Unless there is other evidence besides the coolant the vehicle should have the coolant thoroughly flushed and replaced with another long life brand. If you have owned this vehicle for at least half its life, and never had to replace the intake gaskets it is very likely they will fail in the next year or two. This engine has its share of internal issues with piston slap and sunk lifters, which can get worse much faster with coolant in the engie.
Wednesday, November 18th, 2009 AT 6:17 PM