Recently I replaced every part in my cooling system as well as belt tensioner, idler pulley, serpentine belt. I used a spill free funnel to fill the system with 50/50 coolant, I turned the heater on high, started the car and with the use of the spill free funnel burped the system. The heater was working inside the car, the temp gauge was rising to operating temp all seemed to be going as planned. I completed burping and went for a short drive the temp gauge started to rise, the check gauge light came on, the temp gauge started to jump around and all of this was happening with a couple of minutes of slowly driving around my community. I have changed the temp sensor unit and temp sending unit no change. I read alot about air in the system may cause this failure, so I burped the system again with the spill free funnel. No change in failure condition. I bought an infrared thermometer and when the check gauge light came on I stopped, popped the hood and measured the upper rad hose, lower rad hose, heater hoses no reading above 180 degrees. I am lost with all I have done resulting in same failure. Any ideas?? Please let me know. Many thanks.