!996 Cutlass Supreme overheat issue

I have a '96 Cutlass Supreme LS with an overheat issue. The temp gauge goes way up, the dummy hot light comes on. I replaced the water pump and the radiator cap. Then I ran it for awhile and still no heat, but the temp gauge stays down. I then purged the radiator cap and squeezed the radiator hoses. Then I have great heat and the temp gauge stays down. After driving it about 40 miles the hot light comes on again and the temp gauge goes up and again blowing cold air. Can anyone help or have suggestions? I heard there is a sensor that could need replacing, but am not sure where it is.:headshake

Did you open up the bleeders to get all the air out, 3.1 I assume, there is one on the T stat housing, and another one also I believe. Might want to remove and check the t'stat for full opening also. Was the coolant sludgy/dirty?

are you talking about coolant sensor if so it's usally in the side of radiator.and if it shows on dash low coolant. have you had radiator flushed? and is fan working?

max- the coolant looks clean.
scrapper- fan works and thanks for locate on thermostat will look into replacing yes i thought the gauge read low is there a higher temp stat i can put in or is there only one specific one? thanks for the help guys! my "mechanic" says it was working ok today but will find out later tonite if another 40 mile drive will kick up another problem with overheat issue

195 thermo is called for on this car.

The thermostat was replaced less than three months ago. I found out this vehicle was in the shop on 9/18 and was checked for overheat issue. New plugs and wires were installed but no mention of a fix for overheat. It now will dummy light a hot read but show normal on the gauge. It is blowing cold air but if I bleed the radiator cap a little then after a bit I will get lukewarm air and the gauge will go back down to like cold. Then it will go back up and say its hot and the car will start cutting in and out for a while and then run fine again. I tried to crack the radiator cap to maybe purge some air out of the system and then I get a little bit of heat but then it goes back to blowing cold air but the dummy light might still be on saying HOT. Any other thoughts out there?:headshake

scrapper- I was wrong, the fan is not working. Dont some fans not run all the time? I thought that maybe in cold weather they are not supposed to be on because the air is already cold, right? Anyway, the fans are not working today when I started it up and let it run for maybe 10 minutes.

oh yeah the radiator was flushed two months ago by a reputable shop but no mention for a fix for the overheat issue.

Fans come on at 222 or with the ac.

Thanks maxwedge for the info. Hence, my name renchhednot! Ok, I found the bleeder valve on the bypass tube, I think but cant locate the other one. Is it like the other one with a standard screwdriver to open?