Hi,

Long time lurker, think this is my first post.

94 Buick Roadmaster Wagon 350 ci, all power, etc.:

Yesterday, about 8 highway miles away from home, stopped at a
stop light.  As the light turned green and we turned left, I
heard a noise like a little 4 cylinder engine revving up as it
left the light.  Glancing as we turned, I thought it was a
strange noise for a Ford pickup to make.
  Around the corner and the noise continued, now noticeably
following our own engine speed.  At the same time I groaned
loudly because I smelled what I thought sure was antifreeze.
  We were going to Lowes.  The noise subsided slightly as we
crossed the parking lot and the smell of antifreeze also
subsided.  Parked, the noise wouldn't come back but the
antifreeze smell was unmistakably present.
  Nothing wet under the heater core when I looked; that was
good.  Popped the hood, all was dry and there was only the
slightest odor of antifreeze by now.  I keep it pretty clean;
everything looked fine under the hood.  Belts OK, levels OK,
etc..  No dash warning lights.  Serpentine OK, ac compressor
spinning OK.  Coolant appears slightly low but haven't checked it
in quite awhile.

  Loaded the wood, started out, and the previous noise AND
antifreeze smell was gone.  As I recall, antifreeze smell lingers
afterwards, right?
  So was the air conditioning I quickly realized!  It blew only
hot air; not the faintest hint of cooling; in fact, it was hotter
than the Vented air by a few degrees.  OUtside temp was about 94.
  So, I would surmise that both the noise AND what I thought was
the odor of antifreeze were connected.

Anyone have a guess what happened?
Was the smell actually the ac compressor filler?
What would have made the engine-speed related sort of "tappet"
noise?
Why is the noise gone now?
An educated prognosis?

Thanks in advance for any relevant comments; can't afford to fix
it right now, so was wondering if this was a diy or go directly
to the shop, skip payday scenario.

Pop`