Oil in Radiator

[cags]

99 Yukon with 5.7 liter engine 156,000 miles. There is oil in the radiator. Oil is not milky either in radiator or in engine. It is engine oil and not tranny fluid. Idle vacuum steady 21" and compression test reads all cylinders 160 to 162psi .With these figures I,m assuming not a blown head gasket or intake manifold gasket but cannot rule them out..Engine oil cooler (integral part of radiator) has been tested with no leaks found using a pressure of approx. 60-65psi.No external leaks detected on block or radiator. Engine idles smooth and no smoke coming out of tailpipe. Hairline crack in block???
Any comments will be welcomed. Thanks Cags

 

[dachrist]

If its not the oil cooler, most likely its the intake manifold gasket. I don't think a compression test would show an intake leak.