Radiator

If oil is coming out of the radiator reserve tank, there are 2 possibilities.

1. Someone mistakenly added oil into it.

2. You have oil in the cooling system and that indicates either a bad head gasket, cracked head or cylinde block.

Check if there are any oil in the radiator and engine oil.

Just to add to this one its very common for the oil cooler under the intake to leak oil into the coolant. All the ones I have seen have had oil in the coolant on those engines have been a leaky oil cooler. You will have to remove the oil cooler lightly pressurize one side of the cooler and hold your finger over the other side and submerse it in water and look for bubbles. Just to add to this one its very common for the oil cooler under the intake to leak oil into the coolant. All the ones I have seen have had oil in the coolant on those engines have been a leaky oil cooler. You will have to remove the oil cooler lightly pressurize one side of the cooler and hold your finger over the other side and submerse it in water and look for bubbles.

These engines are pretty notorious for developing cracks in the heads. Sometimes they can be repaired but you need to get it diagnosed properly before you do a lot more damage to it.