4kq overheating - still

[ben swann]

I have been at this overheating problem in a '85 4kq for too long and
this problem perplexes me.  I am beginning to think the problem maybe
internal to the engine.

So far I have tried 3 different radiators - the last from a known
running 4kq which kept guage near center except on very hot days with
AC.  Still it overheats - not so drastically now, but after 15 min
driving, the guage will begin to peak and the car will vaporlock and
not restart if I shut down.  Head seems to be getting unusually hot.

The top of the rad. gets warm/hot, but the bottom remains cold enough
to condense moisture.  The lower rad hose gets hot near the water pump
outlet on the engine and gets progressively cooler toward the bottom
where it enters the radiator.  That same hose seems very pressurized
when hot, as does the upper hose which goes to the cooling neck.

The heater blows warm, but not as hot as I would expect - Hmmm.

So far I have tried new thermostat and just have been running without
one 'til problem resolved - it definately is better without t'stat, but
that is not the problem.

Both main hoses as well as overflow tank hoses are free and clear.
Engine takes water from upper hose and expels out the lower hose when a
garden hose is fed in and vice versa.  I have not seen any kind of
obvious suction when hoses were put in tank of water with engine
running, probably water pump lost prime as it is hard to duplicate the
closed system.

New rad. fan switch(es) 3 so far make no difference.  I have to trigger
on the fan with switch I've wired in to make fan cool to keep
overheating at bay.  I drove the car during the winter and I started to
notice the problem, but I guess it was cold enough out to keep from
overheating.  Now with warmer temps it has become unmanageable and I
can only drive the car for short trips.

I'm afraid I need to pull the head, but wondering what I might find.  I
don't want to go through another futile excercise like I when I changed
my other nice motors if I have to do that.  Is there a possibility that
an incorrect head gasket may have been installed? Any other clues
before I do something drastic?

The engine runs fantastic otherwise, with no lifter tick, smooth and
good power.  Where do I go from here?  I am a few steps from having
another parts car here, but this ones too nice to cannibalize.

Ben