We have two auxilliarys that before drydock and full overhaul were filled with distilled water and unitor cooling water treatment. Post overhaul both have the same problem.
Post major overhaul we are now using hard shore water.
Since the overhaul almost immediately water has turned dirty/brown/orange colour. Before DD water was always clean.
We have various things checked by the outfit who overhauled them for leaks but nothing has been found. The system runs a LT/HT mix with a plate cooler on the LT circuit. Other side of plate cooler is LT again which is completely clean.
Pressure tested water cooled exhaust manifold, air cooler, Checked pumps, thermostat valves, changed all heads again. Cylinders are always dry on head removal.
We have flushed the cooling system through various drains around the cooling circuit until water run cleans. Circuit capacity is >100ltrs and have flushed maybe 5m3 over the last few months. Once engine runsm within 5mins water is back to the same dirty water.
Has anyone had anything similar or ideas to try?
Thanks in advance