TD5 oil coming out through the coolant reservoir

Looks to be about 32mm, Thanks!

Hi all i know its an old topic but i have recently got a td5 Disco and removed the egr and cooler and replaced a few hoses just for good measure. when filling the the coolant i had an oily type liquid coming from the bleeder which seemed to mix ish with water in my hand but after spreading it across my hand to dry it did not leave an oily film on my skin, Is this old coolant or should i have bigger concerns, she drove perfect and no rise in the temp gauge. It was charcoal in colour not white or milky or black.