Cat 3304 getting coolant into oil, done a pressure test and coolant is running down between piston and liner, couldn’t find anything that looked wrong with the headgasket and have the head sent off now for testing, has anyone else had this problem or have any thoughts on it
Perforated liner, probably. Usually caused by erosion due to poor coolant condition. When you get it apart, don't be surprised if the lower sealing land is in bad shape as well.