IIRC the CRD has:
1. a transmission fluid cooler in the bottom of the AC condensor so there should be no possibility of what you are seeing being tranny fluid.
2. an EGR cooler on the right, viewed from the front, rear of the engine but given that it's function is to cool the EGR valve as it lets some exhaust gas into the intake I don't see how oil could get into the coolant there.
3. a oil cooler on the left side, viewed from the front, of the engine below and forward of the turbo. Oil could get into the coolant from here.
Items 2 and 3 are visible in some of the images at
viewtopic.php?f=98&t=74594&p=781854#p781854If you have only a very small amount of oil I'd suggest a complete flush of the coolant system:
1. drain the coolant
2. add a good coolant flush, refill with demineralized water (available at any grocery store), operate the engine as recommended by the flush stuff
3. unfortunately the coolant system "low" point is below the radiator drain so you will need to repeat the fill and drain cycle, no need to add more flush chemical, multiple times to get all the old stuff out. How many - at least 5 based on related experience getting rid of non-spec antifreeze.
Alternatively you can try a Prestone Flush and Fill kit. It "should" work. I've used it on other gas and diesel engines just not this one. Look at
viewtopic.php?f=5&t=56486&hilit=citric might try minus he citric acid.
I'd also pull the coolant tank and wash it out. If you do a) the tank engages a metal flange on the bottom so it must be pulled forward before it can the lifted up and b) as you lift it up be sure to unplug the wires that go to the coolant level sensor on the bottom of the tank.
Once the system is completely clean refill with HOAT coolant (Zerex G-05 or equivalent) and demineralized water at a 50/50 concentration. If you fill the coolant tank to about 1" above the midline flange after several drive cycles air will purge and the coolant level should settle to about the midline flange, add coolant if needed.
Monitor coolant level and if any more oil shows up and go from there. FYI checking coolant and oil level should NOT be done with the front of the vehicle on even a slight up slope, like a residential drive, as doing so will, I know, give you false low readings. Take readings only on a flat spot.