Some of the classic signs of head gaskets taking a break from assigned duty:
1.Combustion gasses blast into the coolant system and out the overflow
  (temp gets a little hot, too). "Gurgling coolant" is a worthy description.
  Check for hydrocarbons in the coolant by waving a smog sensor wand over
  the open overflow tank opening.
2.Leaks out the sides of the heads. Look for coolant on the ground
3.Coolant disappearing and white smoke out the exhaust. Watch exhaust
  when starting, especially cold
4.Coolant disappearing and no white smoke out the exhaust.  Very mysterious
5.Compression low and one of the above, although sometimes the compression
  can seem just fine, especially if the engine is not hot

Prevention?
1.Run 50/50 phasphate free coolant.
2.Change coolant every year.
3.Keep coolant topped up
4.Some people toss in ceramic sealer, both preventatively and
  correctively.  Sometimes works for a while.
5.Appeal for mercy to the forces of nature that control chemical reactions

And there are others much more knowledgable who probably know more
about the signs and prevention methods, and I'm hoping they will add
to the lists above.

Cheers, Tom Neal

On Sat, 1 May 1999, Brent Christensen wrote:

> After running around town last week in my Syncro Westy, I noticed that right
> after I shut off the engine, I heard gurgling noises from the cooling
> system.  I quickly ran to the back, lifted the hatch and noticed that
> coolant seemed to be bubbling into the expansion tank.  It stopped after
> about 45 seconds, and as I recall the level in the over flow tank appeared
> to be normal.  This is the only time this has happened, and it hasn't
> happened since.  Is this normal, or do I need to "burp" the cooling system?
> Could it be a sticky thermostat?
>
> PS - the cooling system, engine, hoses, H20 pump were replace about 25,000
> miles ago.
>
> Thanks
>
> Brent Christensen
> '89 Syncro Westy "Klaus"
>