Heater line broke while driving and over heated up to 217 per tuner, fixed the line and filled with coolant now the temp gauge on the dash after warm up ond on the road will jump up to 200 then drop to 180 real fast prior to over heating engine ran at a constant 180 unless towing, temp sending unit? Thermostats? The tuner prior to over heating would drop or rise 1 to 2 degree's at a time, after over heating sometimes it will jump 4 to 5 degree's. Any help out there?