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.
Car Problem Reports
GMC Suburban 2500 Intake Manifold Gaskets May Leak Coolant or Engine Oil
GMC Suburban 2500 Problem
Engine Affected: 7.4L V8
Average Mileage: 100,666 mi (50,000 mi - 132,000 mi)
Visitor, 1999 GMC Suburban 2500, 7.4L V8, 50,000 mi
Has been leaking for past 45,000 miles only enough to smell antifreeze after engine is hot. Does not leak enough to drip on driveway. Requires pint of coolant every second oil change (8,000 - 10,000k miles).
Visitor, 1999 GMC Suburban 2500, 7.4L V8, 132,000 mi
Intake manifold gasket failed and was leaking outside on the rear of the block passenger side. I was told that original gaskets deteriated due to use of Dex-Cool antifreeze. gasket was replaced and new antifreeze added, no problem so far