I have a 73 power stroke that I suspected was losing antifreeze in the oil. I put 20,000 miles on the truck in three years. The truck now has 63,000 miles on it. I use the truck for hunting fishing and vacation trips. After I take it for a long drive it's always goes to add on the coolant system. I had an oil analysis done and it's showing any freeze in the oil. Testing facility recommended changing oil and checking again at half interval which would be 2500 miles. I bought a warranty far it when I bought the truck took a dealer and they hot and cold pressure checked it. Said they didn't find it losing any pressure. I asked them when a hot engine cools down it loses pressure and they said they pump it back up to repressure then. They didn't have a good answer when I question them on this. It could be losing coolant into the oil at some point when it's cooling down. Some people I've asked said it's the head gasket. I guess it doesn't make sense that it would be oil cooler because oil pressure is higher than coolant pressure. But if it leaked only had a certain temperature when the engine was shut off I think it could still be possible. Looking for somebody with some experience with this for some help. Would like to narrow it down before I tore it apart. Thanks

 

Seems like your truck sets a lot with only 63K on it. I'd bet oil cooler. It's easy to repair and won't hurt anything if its not. Most trucks stay at the add line anyway so I won't worry about that. Maybe change the cooler O-rings, then change the oil and send in another sample to be tested. Have you done any injector work lately?

 

Welcome to FTE A lot of great experienced group of guys here to lead you in the right direction. I would also assume it would be the oil cooler. Its easier to deal with then a head gasket but that's where I would start. Others will chime in with their knowledge. Stay tuned.

 

It could possibly be the oil cooler. When you shut the engine down, the oil system loses residual pressure in a second or two. The cooling system stays pressurized until the engine cools significantly. It could also be front cover seals or head gasket. I would think the head gasket would be the least likely.

 

As I read this, you said "...and it's showing any freeze in the oil". Should I interpret this as the oil analysis showed NO antifreeze in your oil? Have you tried just not refilling the degas bottle when it goes low? Does it go lower after another trip? Mine likes to sit at about an inch below the full mark.

 

No work has been done on the injectors. When pressure testing the coolant system hot it holds ,when cold it holds. When it's going from hot to cold systems will loose pressure anyway. So it could be leaking at that point but would be hard to tell. Coolant system is not being contaminated with oil and you would think if it was going one direction with engine off the oil pressure would overcome coolant pressure and introduce oil into the coolant system. I figure I will pull the cooler off blank the coolant ports and pressurize with a valve and gauge see what it does. Reseal it while I'm at it. Something that I hadn't thought of but should check is the drain port on the water pump. I know gear driven pumps can leake anti-freeze into the crankcase. Thanks for everyone's help I really appreciate it

 

Head gaskets rarely go out, even when people torture the engine with modifications. There are very few places where oil comes in close proximity to the oil, and the oil cooler is the most common source of cross-contamination. It's possible for an oil cooler O-ring to leak one direction and not the other, so the 15 PSI in the hot coolant can leak backwards into the oil when the engine is off.


Many of us lose coolant if we try to fill to the full mark, so we stopped adding coolant to see where it lands on its own - and it just sits lower than the line forever.


It's remotely possible your oil filler tube has a bad seal on the pan, and the venting of coolant drips in there. That's a stretch, but I'm trying to theorize how you can have such a small amount of coolant in there that only a lab test can detect it. Usually... a real crossover of oil and coolant makes a big mess that's easy to spot.