I have a 96 ford Taurus. The car keeps overheating. I replaced the thermostat added antifreeze and it continued to overheat and the antifreeze started coming out of the Reservoir

It sounds as though you may have a flow issue in your cooling system. At faster speeds there is obviously more air crossing the cooling fins on the radiator which would explain why the temp goes down. Is the system building pressure when it's up to temp? The thermostat may be froze up or there may be flow issues elsewhere in the system. Is there heat in the vehicle meaning you have flow through the heater core? Also when adding antifreeze, make sure it's a 50/50 mix with distilled water. Having a higher concentration of 60% coolant will inhibit the coolant properties of the antifreeze and cause corrosion problems.

Quick check: Does the Engine cooling Fan come on when you turn on the AC? Vehicles don't need a fan over about 30 MPH but require fans for city driving and Air Conditioning. Flow issues in this engine are rare except for a plugged Radiator or worn out Water Pump impeller. If it cools on the Highway - look at the fan(s) first.

2000 Ford Taurus Head Gasket Repair/Replacement (Tutorial) - Intake Gasket (Tutorial) - Torque Sequence - (Tutorial) - - - Over Heating Issues with Coolant Overflow Reservoir/Cap. Bubbles in the Coolant system. Too Much Pressure, caused by a head gasket leak. Misfire Issues. This Video Covers : - Head Gasket - Intake Gasket - Coolant/High Pressure (Over Flow) - Torque Sequences - High Pressure Coolant System - Rocker Arms - Thermastat Length of Video: 1:32:56 Average Cost: (Blown Head Gasket) - Self Fix - Roughly $200 - Shop Fix - $1200-$1600 Full Tutorial Video https://youtu.be/jq2ngudVFew