I have been loosing small amounts of coolant over last few months. I changed the oil today and I could see that it has been leaking down the back of the engine close my the oil filter. Anyone got any idea what this would be? Is this a common leak??

Check near the oil filter .. the filter adapter oil cooler assy uses engine coolant to cool the oil ..

See this thread .. http://www.dieselplace.com/forum/showthread.php?t=356699

I will check that first. Kinda thought it was coming from a little higher up but that could for sure be it.