Head bolts leaking

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Check engine light stays on, over 6 mos., changed gas caps and thermostat. Going through coolant, noticed oily residue in radiator, and on head bolts. Also, losing oil. Car does not overheat, drives well. Very cold here, and I can tell when coolant is low, cool air blows out of dash vents. No underbody leakage, and top radiator hose is hot, lower is cool. When we flushed radiator, "vanilla pudding" texture came out with very little oil. Don't know what ishe happening.