Oil in Coolant..Volvo Tamd74 EDC

When it rains it pours...

Many of you have chimed in on my thread where I think I dodged a bullet on a transmission issue. Then another thread where I broke an exhaust elbow. Well, I got both elbows replaced along with the ancillary things that needed to be done and went to pick up the boat this weekend.

Previously I noticed I had been losing a little bit of coolant on my port engine (elbow issue was starboard). Expansion tank was empty and I've probably put a quart of coolant in since a cooling system rydlyme flush/refill at the end of last seasons (maybe 40hrs ago).

So I was checking things over and popped the coolant cap on top of the engine to check the level there since expansion tank was empty. I found it covered in oil. I dipped my finger in and got to coolant pretty quick. So estimating 2-3 ounces of oil that settled at top.

Needless to say I left the boat at the yard and advised them of the issue. Hopefully they're looking at it today. But I like to get my ducks in a row.

As I understand it oil in coolant could be one of 3 things... head gasket, cracked head, or oil cooler.

I change my own oil at the end of each season and have never noticed anything odd about the used oil. But I pump it into buckets and don't always see it that closely. The yard JUST changed the oil as part of this exhaust elbow service and didn't say anything about the oil looking odd but not sure how carefully they looked either. And I'm not losing much coolant so not sure how noticeable it would be in the oil (7+ gallons). I would also note I've never had a problem with temps.

My best guess is and I am hoping it's the oil cooler, as I think that would be cheaper to replace than tearing down the top end of the motor. Seems like that is the most likely culprit given the quantities I seem to be dealing with.

I welcome any thoughts and armchair wisdom on the issue and the diagnostic process. I don't want to just change the oil cooler out as it's a pricey part so not sure what the process is. At $125/hr I'm hoping it's not "take stuff apart until we find it".

Thanks Capt Ralph. Not soot. Oil. Black used oil. I don't believe turbos are water cooled but honestly I'm not sure. Oil may well go to the lab. I have test kits on the way.

Interesting, thanks. No thermal blanket so I get could be liquid cooled? Will add it to my list.

Quick look confirms that turbo is indeed liquid cooled. Not sure if that's a likely culprit but will investigate possibility with tech.