Yikes well hopefully there is an easy fix... how bad is the mixing in the reservoir?
I would start with the oil cooler, probably the easiest and cheapest thing it could be, it only goes downhill from there.
Drain the system, replace oil cooler or have it tested, fill the system with water and shout liquid detergent. Get it warm, drain, fill again with fresh water, get up to temp, drain and refill with coolant 50/50 and pray it was the oil cooler
Threaded Mode
