Take it to a radiator shop that has a laser temp gage - they'll tell you
what the true temp is. I've gone through a bunch of hoops on one car
only to find that the sending unit was bad - it wasn't as hot as the
gage said it was.

Could be the gauge, I know on my Hawk I can start it up and let it run, tap
on the gauge and the needle will jump to the right and stop with each rap on
the glass and peg out all the way to the right.  This is with a completely
boiled out block and new radiator.  Never had the engine overheat once.
I've heard several other people state the same problem when I've brought it
up.

Lee

If the gage is correct, it's time to pull the freeze plugs and clean the
block out.

Don,

it depends on the car.  In my '55 coupe, the gauge runs at 3/4 when
with my laser thermometer it says I'm just a hair under 180 degrees.  I
believe the gauges were originally calibrated to read at exactly mid
scale with a stock thermostat, which for earlier cars was 160 degrees
and the latest models 170 degrees.  Since 170 degree thermostats are no
longer available most people run 180s therefore the gauge may read a
little high.  For piece of mind try to measure the engine temp. at the
top radiator tank or thermostat housing and see where you're at, either
with a laser thermometer or a candy thermometer.  If it's within a few
degrees of the thermostat rating I wouldn't worry about it.  You could
put a small resistor inline with the sender wire if you want to adjust
your gauge to read mid scale.

nate

At one time I bought three aftermarket temperature sending units,
marked TU-2 on the box at a generic swap meet.  Two made the guage read
3/4 toward hot.  The other read 1/2 way up.  This was with a verified
160º thermostat and a freshly cleaned block with new freeze plugs. A
glass thermometer in the radiator neck confirmed I was cooling OK.  I
guess you cannot assume that a new part is right, just because it is
new.  KK