Coolant mixing with oil?

[Jay Whitely]

Hello all,

Last week, I was trying to figure out if I had a blown
head gasket or just a blown turbo.

Well, I installed a brand new turbo this time and all
the smoking pretty much went away.  I noticed that
when I was priming the oil pump and expelling all of
the air from from the turbo with the oil drain
detached, there was coolant coming out of the oil
drain hole of the turbo.  This would lead me to
believe that there was coolant in the oil.

The only way I know of how to get coolant in the oil
is by having a blown head gasket. I removed the head
and had the machine shop pressure test and inspect it
completely. Their findings were that the head was
*NOT* warped and the head gasket did not blow.

Here is the odd part. As soon as the car died the
first time on the side of the road, I checked the oil
on the dipstick and it looked clean.

Only after installing the "new" turbo did coolant
appear on the dipstick.  I had a turbo shop install a
new CHRA from Turbonetics with the old turbine and
compressor housings.  I did note that the CHRA was
already a bit rusty and kind of used looking.

I need to find out how else coolant can mix with oil
in the engine. The deck surface of the block looks
good, as does the head.  Is it possible that there is
an issue with the new turbo that is allowing the
coolant and oil to mix in the turbo?

By the way, I am almost 100% sure that the car
overheated and this is what blew the turbo. The
coolant temp gauge connector had broken loose and the
radiator has a known coolant leak. So, the car was
running hot unbeknownst to the driver b/c the gauge
was reading on "COLD".

I need some ideas here. How is coolant getting in with
the oil, but the head and block surfaces are
flat...and the head gasket looks good?  Someone
suggested to me that the overheating caused the block
to crack internally. The machine shop said that the
block and head would have been warped if this were the
case.

Any help would be highly appreciated.

Sincerely,

=====
Jay Whitely
Tampa, FL
1996 200SX SE-R
GTi-R powered, F-MAX Stage 2