If your car has an oil cooler that's part of the radiator then the most probable reason would be that it's sprung a leak there. You may also have a blown head gasket, which is something that also can open up a connection between coolant flow and oil flow.
You have a blown headgasket or cracked cylinder head/engine block. It can also be a leak at the oil cooler. Its at the oil filter mounting, check that 1st.
(Oil floats) mostly mixes with the water forming emulsion which clogs the radiator.
If it is a water-filled or oil-filled radiator, it will leak fluid.
oil in the radiator water is normally caused by a faulty inlet manifold gasket.
It means that your engine oil is mixing in with your radiator fluid. You probably have water in your oil too. I would take it in and have it fixed.
Overheating, oil in the water of radiator, water in the oil. Less power.
You did not say what you are working on, YEAR AND ENGINE SIZE. But in most cases or designs the water pump can not leak oil into the coolant. The water pump has nothing to do with the engine oil. Does the engine have a engine oil cooler on it ? That would be 2 oil lines just above the oil filter that runs down the side of the engine oil pan a go to the radiator. There are tubes inside of the radiator that oil flows through and they are none to leak oil into the engine coolant that's inside of the RADIATOR. If they are leaking then REPLACE RADIATOR. BUT like I said I don't know what you are working on. Would like to help you with your problem, But need more INFO. NEUTZ.
If its engine oil I would say head gasket or cracked head. Also check under the oil fill cap for a milky color. You can also run the car a few minutes remove the radiator cap see if it smells like gas . Most shops use what they call a sniffer but, Ive found that I can smell the exhaust in the radiator. More than likely head gasket answer is the car automatic? if it is , have your radiator checked to see if transmission fluid is leaking into radiator from oil tank at bottom of radiator if it is engine oil and not transmission oli, you have a cracked head allowing oil to seep into the water chamber a bad head gasket allows water into engine oil, not oil into water
The transmission oil cooler is located in the radiator. A leak that allows oil in the radiator will also allow coolant to enter the transmission doing great harm. Check the transmission , after driving and the oil is hot water vapor will come out of the dip stick tube.
A cracked radiator will NOT put water in the engine and make the oil milky. A bad head gasket WILL put water in the engine and make the oil look milky. That does not neccessarily mean you have a bad engine. Have someone fix or replace the radiator and replace the head gasket. It could be a good engine for a long time yet
sounds like you have a cracked head or cracked block.however, i would check to make sure it is not transmission oil and thereby ruling out a radiator problem
check oil for water and radiator for oil, if engine oil has water miced with it ,the oil will be milky looking same does for radiator