Cooling

[Tom Mandera <tsm1@domain.elided>]

So long as my radiator has had coolant, I haven't had a cooling problem
on my '77 SII w/ 72 304A.  however, after having the radiator flushed
and two damaged tubes replaced, *AND* cleaning out the plugged overflow
vent tube, I'm starting to see problems.

As long as I'm driving, all is well.  I noticed that after towing and
then going to idling in the backyard while parking the towed object, the
temp gauge would climb.  That's fine, I expect that.  I can turn the
idle up via my hand throttle, and all is well.

However, I've also noticed that I can be simply idling and watch the
temp gauge go up.  Bump up the revs, and it's fine.

Another peculiarity - I was idling and watching the temp gauge climb..
and the heater stopped working (usually an indication of low coolant,
but it's still full)

The overflow is working fine.  The upper radiator hose is hot/warm, so
the thermostat is opening (at least, at some point it is)

I changed the thermostat out.. 10k or 15k miles ago (but 3 or 4 years). 
Coolant has been "flushed" through the system several times thanks to
damaged radiators.

The water-pump is the 4-bolt style with a fixed, 7 blade IH fan.  The
fan came off my 196 (original 304 fan had 5 blades)  No clutch (though
I've been thinking about one)

I can grab the fan and push and pull it front to back, and I get a
little play - about what I'd expect from typical "bearing slop."  It's
NOT really wobbly and ready to turn in a number of different directions
like the water pump in my Chevy Luv when it failed.

I haven't added any additional items to the front of the Scout recently
(though I'm contemplating a winch and a new bumper).  It's had a 2-row
radiator for years.. 

Any suggestions on where to look or what this sounds like?

-Tom Mandera, Helena MT
http://www.tmcom.com/~tsm1/scout