i currently have an issue with oily brown residue in my coolant overflow tank, although i have no leaks, no overheating engine, no visible signs that there is a genuine head gasket problem. besides the oil residue in my coolant all is well. what can i do? what should i do?
thank you in advance.
(subaru liberty 1999, 185,000km, no check engine, automatic, 2.5L 4cyl, ej251)