1993 Ford Aerostar temp guage moves li

Engine Cooling problem
1993 Ford Aerostar 6 cyl Two Wheel Drive Automatic

temperature goes up quickly midway stops for three seconds then goes down quickly, half minute to start moving up again.
off the gas for 3 seconds when see temp moving upwards it will slow moving and go back down.
not losing uch water until it starts steam blowin out of coolant
just replaced a month ago so smoked or hammered to death
I was 300 miles from home and was temp problem for about 9oo the bad stuff out radiator.
but on the way home going a lot putting ceramic type block in there 200 miles unstable.

not sure what