GTV6 Brake Leak & Engine Smoking Related?? (kinda long)

["Herbert Neily" <neily@domain.elided>]

     A month ago, I thought that one of my differential half-shaft seals was
leaking transaxle lubricant onto my inboard pad of the rear driver's side
brake caliper.  After ordering new half-shaft seals (currently
back-ordered), I realized that my brake fluid level was way down.  I was a
bit surprised at this, since I hadn't noticed any brake pedal softness or
sinking.   I topped off the reservoir, only to find it nearly empty upon the
next inspection after a couple of short drives.  At that point, I decided
that maybe I had a brake caliper piston seal leaking instead of the
half-shaft seal - no big deal.  So, with today bringing nice weather, I
jacked up the car and prepared to remove the rear brake caliper as the first
step in a caliper rebuild.  Fluid on the brake rotor seemed too thin to be
transaxle lubricant, so I again figured I had a leaking rear caliper.
    I thought I'd try to confirm the leak location first, so I topped off
the fluid reservoir, started the engine to gain brake servo assist, and
pressed hard on the brake pedal for about ten seconds.  Suddenly, I was
aware that the car was surrounded by white smoke.  I shut off the engine and
slid under the car, expecting to find brake fluid on the exhaust system, but
found no leakage anywhere along the entire brake system, including at the
suspect caliper.  Under the hood, the brake fluid reservoir was nearly empty
again.  I fired up the engine again, again with a big cloud of dense white
smoke.  This time, I realized that the smoke was coming out of the tailpipe.
Arrgh!
    My first thought was that I'd blown a head gasket.  However, the smoke
hadn't started until I pressed on the brake pedal.  I checked the coolant
and engine oil, finding no apparent contamination from one to the other.
Today's temperatures were in the 60's and during the colder days earlier
this month, I'd babied the engine until the oil pressure dropped as the oil
warmed up.
    The only way I could envision brake fluid getting into the combustion
chambers would be via the brake servo vacuum hose to the intake plenum.  So,
I pulled the vacuum hose off of the nipple on the servo - I got the familiar
sound of a vacuum release, so I assumed that the servo diaphragm is intact.
Also, I did not find any brake fluid in the vacuum hose.
    I'm hoping that someone can offer an explanation that doesn't include a
head gasket.  I've not had any indication of head gasket problems before and
I'm still mystified as to where the brake fluid went.  Anyone want to
venture a guess?
Bert Neily
Raleigh, NC
'84 GTV6, 68k miles, contrails at sea level
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