Non-scientific oil in coolant test result?!

[indybenz]

Hello,


The subject is an OM616. I flushed the cooling system using citric acid and ran the hose in there til it was clean. I can't remember all the details as it was a few months back but I followed the advice from several sources.


While I was at it I changed all the coolant hoses, thermostat housing and thermostat, head gasket, front crank seal...maybe some other things.



I added the proper coolant.



Since then, the lower coolant hose NEVER gets even remotely warm. Not sure what's up with that. I tested the Tstat in hot water and it opened properly on the stove so I'm not sure.


I have driven it several hundred miles since then and it does get above 100 degrees and turning on the heater on high does bring the temps down a bit.


I checked the coolant and to my great chagrin the coolant has dark sooty stuff in it.



Could be just residual junk from cleaning the coolant system?


Or oil?



Here are my non scientific pics using a dropper and paper towel on a white plate.