Hi. Thanks for using JA! I will try and help you out.
Have you replaced the cooler? Or just tested it?
I see. Thanks for the information.
I would not suspect the head is cracked. It's possible but very rare. Normally when the head cracks, the engine suffers a loss of coolant and does not put oil in the coolant.
The reason I asked if it had been replaced is because I have seen oil coolers test GOOD, but still end up being bad. Sometimes the oil cooler will only put oil in the coolant when it gets very hot during operation. Its hard to simulate that temperature when testing sometimes. I always recommend replacing the oil cooler first to try and fix the problem. The reason I say this is because I have seen many folks tear into an engine for oil in the coolant after testing the cooler and end up not finding anything, then they replace the head and then after reassembly, get oil in the coolant again.
For me, replacing the oil cooler has worked for me 95% of the time when there is oil in the coolant. The other 5% ended up being the trans cooler. Of course I know yours is air cooled.
Let me know if you need more help or have more questions.
Please let me know if you need more help or have more questions.