Coolant in oil

1996 FORD TRUCK
220,000 MILES • 8.3L • 6 CYL • RWD • AUTOMATIC
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GARBAGE MAN
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I have a 1996 Cummins C 8.3L - 210 hp. Last week, doing my pre-check, I noticed my coolant level was almost 1 gallon low (never low). I then noticed the green tint to the oil. I did notice a coolant smell from the breather. I immediately changed the oil and filter. Still can smell coolant lightly from the breather, but an oil change doesn't get all of the oil out. What would cause this? Head gasket? The truck is running and sounds great. Exhaust looks good, no white. There are no leaks under the truck. There is NO oil in the coolant, so should rule out oil cooler. If not the head gasket, could the air compressor leak coolant into the oil? Please give me your thoughts and I will continue to monitor as I need to use the truck this week.
Jan 31, 2016 at 4:54 PM
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CARADIODOC
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Oil cooler is still the best suspect. That is a common problem.
Jan 31, 2016 at 5:07 PM
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GARBAGE MAN
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What is the best way to check it? Wouldn't oil get into the coolant?
Jan 31, 2016 at 5:24 PM
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CARADIODOC
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Typically yes it would, but it depends on the size of the leak and when it occurs. Coolant is still under pressure for a while after the engine is stopped.

Remove the oil filter is watch to see if coolant drips from the cooler.
Jan 31, 2016 at 5:36 PM
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GARBAGE MAN
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When I changed the oil, the oil filter wasn't full to the top like normal. Does the oil flow from the cooler to the filter?
Jan 31, 2016 at 6:44 PM
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GARBAGE MAN
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Are you talking about the oil cooler element casted with the oil filter head? There is also and oil cooler combined with the radiator.
Jan 31, 2016 at 7:01 PM
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CARADIODOC
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The cooler in the radiator is for automatic transmission fluid.

Engine oil doesn't go through the cooler under the filter. Only engine coolant goes through that unit, presumably because the oil is hotter and will give up some of its heat to the coolant to be carried to the radiator.
Feb 1, 2016 at 2:38 PM
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GARBAGE MAN
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So if I pull the oil filter and empty the oil pan, leaving plug off. Then pressurize the cooling system to 10-15 psi. If coolant come out filter tube, it's the oil cooler. If coolant comes out of the pan, it's a head gasket allowing coolant to run down the push rod holes. Exhaust is clean. Is it possible for the air compressor to leak the coolant, pushing into the front cover/timing?
Feb 1, 2016 at 7:13 PM
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CARADIODOC
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All I've ever run into is the cooler under the filter. My guess is you're looking for an unlikely alternative to the most common cause.
Feb 3, 2016 at 5:28 PM