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Coolant in oil questions-please help or share similar


Well-Known Member
August 2, 2009
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City, State
Memphis, TN
Year, Model & Trim Level
2003 Mountaineer V8 4.6L
I'm getting coolant in my oil on a 4.6L Mounty with very little pressure loss at the degas bottle. Pumped the coolant tank to 15LBS and lost 2 lbs in about two hours, but it stabilizes after that. Repeated for almost 24 hours, and lost around 1/2" of coolant from the degas tank. I started the engine for a few minutes, checked the oil, and coolant was present. I've since changed the oil and now looking for the source. Compression tested with a piece of crap loaner guage, but after 5 cycles on each cylinder with a hot engine, all cylinders read 150-165 PSI. The guage leaked down quickly though on all cylinders, so I think the valve is leaking on the compression tester. There is NO coolant externally that I have found, and I've run dye in the coolant.

Tomorrow I'll do a leakdown test, but the engine is going to be cold, will that make a difference?

I've also done a combustion gas test at the degas bottle and ther are no combustion gases present.

If the leakdown test passes, what would be the next places to look?

I've considered a freeze plug behind the timing cover, the oil adapter/cooler, and it could still be intake gaskets even though those were replaced last fall due to a coolant leak externally.

Also, could all this still be head gasket or block related with no combustion gases or oil in the coolant, good compression, and a satisfactory leakdown test?

Sorry for all the questions, but I'm stumped and want this fixed. It's my sons college truck and he's home over summer break.

I was just recently inside one of those engines (4.6).
and (If I remember correctly) there is no oiling ports
through the intakes on these motors, meaning there is
only a couple things that could be mixing oil and antifreeze.
head gasket, warped or cracked head, or worse, cracked block.
but a cracked block is rare though.

either way, you are never going to know for sure until you do the
head gaskets and pressure test the heads (this is what im recommending)
DO THE HEAD GASKETS, or have them done..

let us know what happens