Oil in coolant but no coolant in oil

Check oil cooler first oil pressure is higher then cooling pressure

 

What engine?

 

Start with oil cooler. Think about it. Oil pressure is from 20 to 40 pounds, radiator pressure cap is only a few pounds.Oil will get into water by the pressure difference.

 

Although your theory makes perfect sense and in the past I've had the same question, It's always the oil cooler at fault, this is an industry wide known common fact.

 

It's basically just 4 orings that separate the oil and coolant on 466 coolers. They go hard and break down after years of service. Chances are if you kept running it in short time yes, you will also have coolant in the oil too. Easy job to reseal, I would be doing that before an air compressor.

 

444 and 466 are same basic design, 466 is bigger. As far as the seals only or cooler and seals, you would need to test it. If you want to cover all your bases, you would replace the cooler. For the most part, they are a good cooler and chances are you only need seals. I'm not sure on a cooler price so I don't know how expensive they are to replace.

 

Do you have an oil cooler on your transmission? If so, I would check that too.