93 100 CSQW: Overheating / Coolant Loss

[TEX TERRY, II]

From: "Eric Billing" <eric.billing at eds.com>
(snip)
Looking for help diagnosing the sudden problem on my wagon (132K miles).
>>>
Next day (after getting some coolant) I filled the reservoir (added about
1/3 gallon) and idled the car for about 10 minutes. As the temp came up, so
did the coolant level in the reservoir. A few iterations of burping out the
air resulted in some coolant expanding out the cap of the reservoir, which
was my only visible coolant loss. I let the car cool down, re-filled with
additional coolant (about =BC gallon) to about mid-way between MIN/MAX, and
started her back up. Idled for another 30+ minutes. Temp gauge looks normal
(straight up). No leaks at all. Again the coolant expanded to beyond MAX,
but did not come out of the expansion tank. I let her idle for another 15
minutes or so. Temp gauge stays in the normal (I think) spot. Absolutely no
leaking back by the firewall.
>>>
So this morning, with spare bottle of coolant in hand, I left for work. 32
degrees here in Mpls. My commute is mostly highway for about 40 minutes.
About 15 minutes into it, I notice that the temp gauge is pushing towards 1
o=92clock. Another 15 minutes, and it=92s a little higher, but appears to
h=
ave
stabilized (definitely above normal, though). AT this point, I=92m
starting=
 to
smell the =93hot smell=94 of coolant on the exhaust manifold. As I pull
int=
o the
office parking lot, the coolant/overheat warning light comes on. I pull
into
a parking spot, pop the hood (car still running) and observe slightly low
coolant level in the reservoir, and steam rising from the firewall area.
Down below reveals a series of dripping from both sides.
Questions:
a)       Obviously, my ride to work was a little more stressful than idling
in the driveway. However, both were for 30+ minutes. Would the absence of
symptom in the driveway scenario suggest anything useful?
b)       The coolant level was not terribly low this AM=97yet the
overheat/coolant light came on. This, to me suggests overheat more than low
coolant. Make sense? If so what does this suggest?
c)       Any suggestions for additional things to check/test for?
(snip)

Have you checked the heater coolant circuit - hoses and valving?  You did
not mention having the heater turned on while you were testing in your
driveway, but one would think that you had the heater on while driving in
the cold to work.  It sounds like you have a leak at either the heater hose
connection at the firewall, or at the heater shutoff valve.

Tex Terry, II
83 5kt sedan (non-quattro)
Franklin, PA  USA