Oil in coolant

My 1989 Ford Probe 4 cylinder with 183K miles appears to have oil in the coolant. There is no evidence of coolant in the oil. An analysis of the exhaust shows a clean burn. There is a leak that appears in the vicinity of the connection of the lower hose to the block after the engine cools but not when it is hot. I am loosing a quart of oil every 1500 miles with no evidence of burning or leaking other than the oily coolant leak. Is there a place where the oil and coolant passages are in close proximity and could crossover? When running, the oil runs at a higher pressure than the coolant but when shut off the oil pressure drops to zero and the coolant stays pressurized until cool down. Wouldn’t this cause a reverse flow?
Help!