The intake manifold gasket may develop and external engine oil or coolant leak. In some cases, an internal coolant leak may occur causing coolant to mix with the engine oil. Running the engine with a coolant/oil mix may result in engine damage. Replacing the intake manifold gasket should correct this issue.Google+
Car Problem Reports
GMC Suburban 1500 Intake Manifold Gaskets May Leak Coolant or Engine Oil
GMC Suburban 1500 Problem
Engine Affected: 5.7L V8
Average Mileage: 178,994 mi (100,000 mi - 258,000 mi)
Visitor, 1997 GMC Suburban 1500, 5.7L V8, 258,000 mi
coolant leak in manifold gasket, internal and external. Coolant in oil. Blue Devil did not help, Bar's head gasket fix helped a lot but did not seal the leak, which is rather greater as engine warms with heater of. I may have to replace gasket as you suggest.
Visitor, 1999 GMC Suburban 1500, 5.7L V8, 140,000 mi
Engine began over heating and could be controlled by cabin heat being blown on high. So replaced thermostat but noticed it did nothing and then water/coolant leaking from underneath. Service garage determined manifold gasket failure. Have not taken action as of yet since total engine replacement was advised. Very expensive to do so.
Visitor, 1999 GMC Suburban 1500, 5.7L V8, 100,000 mi
Engine blew. Coolant in engine due to cheap parts (gaskets, etc) installed in that model year. Common problem that should Chevrolet have informed buyers of. If they had we would have been able to save engine.
Visitor, 1993 GMC Suburban 1500, 220,000 mi
intake gasket was old...new gasket fixed the problem
Visitor, 1996 GMC Suburban 1500, 5.7L V8, 217,950 mi
heading in for my 2nd intake gasket replacement.
Intake manifold gasket leaking coolant to exterior along front of both heads. Diagnosed location of leaks with cooling system pressure tester.