Oil in coolant

Hi
I'm new to the forum and Freelanders, my wife has a 2003 TD4 which has black oil in the coolant expansion tank, the car doesn't overheat so I am hoping the fault is with the oil cooler, I have replaced the oil cooler and flushed the cooling system and am now waiting to see if this cures the problem, my question is that there is a constant flow of coolant coming back into the expansion tank from the smaller pipe, should this be happening or is this another problem?

Thanks

Carl

yes. it shd

Thanks, I was thinking that it might be a head gasket problem causing it.

coolant on small hose is coming from the top of the radiator,
it also helps to keep the rad free of air pockets