Today's case, are the doctors in?

[Michael Murphy <mmurphy@nais.com>]

Dear qlisters . . .

Doctors, today's case presents as follows:

89 100 nonQ, complains of OVERHEATING

BACKGROUND -
Never had a problem with coolant temp. 
Don't know if thermostat ever replaced (probably not).
Cooling system flushed/refilled 10/96.
Gauge always registered dead center.  When traffic/OAT got too
much, fan would bring temp back into range.

8/11 - 8/25 car sat immoble at mechanic for part.
            Aside - battery drained (interior light stayed on).
            Seems to have healed OAT sensor and scrambled display
problem
            as they worked today (but we'll see).

8/26        Got car back (repair had nothing to do with cooling system)

SYMPTOMS -
Runs warmer. Gauge needle slightly above mid point.
Air temp was about 85 max (OAT indicator around 90).

Changed oil & filter and took off. Running warm as above
W/FAN GOING ON MORE THAN USUAL WHILE DRIVING. Driving local w/min
stop & go (30-40MPH).

Temp gauge starts going up, steam observed.
Stopped almost immediately when H2O temp warning displays.

Found coolant tank cap loose and no coolant in tank.
NOTE - FAN GOES ON SEVERAL TIMES WHILE CAR WAS OFF.
Filled tank with coolant (proper mix) and took off. 

Temp OK but starts to rise slowly after several minutes of driving
(30MPH w/ only one stop).
No steam this time but get temp warn display and needle
climbs to 2 clicks before H. FAN DOES NOT GO ON.

Drive home with ECONO heater on HI and max fan. 
Temp gauge does not go any further than 2 clicks from H, but did
start to rise when heater turned off.  STILL NO FAN.

At home, no leaks, no steam, tank level full. FAN GOES ON 3X W/ENGINE
OFF.
After 1 hour tank level dropped 1/4" assumed back to radiator.

Still no visible leaks on ground on hoses, etc., no coolant in oil.

DIAGNOSIS? - 
Thermostat FUBAR while sitting for 2+weeks at garage?  I think it's
stuck partially open, or can not open completely.
Any seconds?  If so, recommendations re: which thermostat to get (174 or
187F).  I live on Long Island - OAT lowest 0, highest 100F.

RE: Where the H8$% is thermostat?
Pls correct if wrong, thermostat housing between plugs 1 & 2.
Has upper radiator hose attached (like the rest of the world).  
H2O temp sensor/sending unit attached to housing pointing up.
Thermostat faces down with several wires running out; connects to
housing with "big mother" brass nut?

If you have a differing diagnosis/view, pls advise.

Thanks in advance,
MJ Murphy,
89 100 nonQ 71K miles (no Bentley yet)
86 Jeep G Wagoneer 194K miles (beat on theromstat housing and she
works).

PS Sold 86 4kq over weekend to deserving college student who begged me
   for 3 months. 140k miles, w/brother inflicted engine damage, dead AC