My brother has a 93 camaro with the 3.4 liter motor. His temp gauge was faulty so he picked up another cluster. The old gauge would jump around this one is steady but just keeps going up. The engine temp was tested and was fine and the car doesn't seem to overheat. He was adding coolant today and while he was bleeding the system we noticed smoke coming from the radiator. I. Top of that it started to overflow and bubble like crazy. Anyone have any ideas as to what would do this and why the temp just keeps going up?

 

I guess if the gage goes up and the engine boils over, then the gage is OK. There are many reasons for the engine overheating. Are you filling up the radiator by removing the radiator cap, or are you just adding coolant to the overflow bottle.
1) Radiator not filled up completely
2) Coolant leak
3) Bad radiator cap
4) Fans not coming on
5) Bad temp sensor
6) Bad water pump (not common, unless it is leaking)
7) Slipping accessory belt
8) Clogged radiator
9) Bad head gasket
I am sure there are more
5)