Temp gauge shows hot even if engine has been off overnight?

there is no fuse. you may have a bad sensors or loose wire.

Sounds like air in the cooling system.What year camaro?What engine size?Have vehicle running at operating temp and slightly open cooling system bleeder (if equiped) leave open until you get coolant only and no more air.If this doesnt work have cooling system pressure tested.Could be a blown gasket somewhere.Good Luck!!!!!

YOU NEED BLEED COOLANT SYSTEM.CHECK COOLANT LEVEL IN RADIATOR.ADD MORE DEXCOOL UNTIL COOLANT LEVEL IS CLOSE TO RADIATOR SPOUT.CRANK ENGINE LET IDLE UNTIL TOP RADIATOR HOSE GET HOT.WATCH TEMPERATURE GAUGE.IF TEMPERATURE GAUGE START RISING TO HOT ZONE.TURN OFF ENGINE.LET COOL DOWN.USE LARGE RAG SLOWLY OPEN RADIATOR CAP A LITTLE AT A TIME UNTIL ALL PRESSURE RELIEVED.REMOVE RADIATOR CAP.ADD MORE COOLANT.CRANK CAR AGAIN LET IDLE UNTIL TOP RADIATOR GET HOT.KEEP EYE ON TEMP.GAUGE ALSO.WHEN TEMP.GAUGE STOP CLIMBING.YOUR COOLANT SYSTEM BLED.WHEN DONE LET CAR SET A WHILE CHECK COOLANT LEVEL.ALSO FIRST THING IN THE MORNING CHECK COOLANT LEVEL AGAIN.AND BESURE ADD COOLANT IN THE OVERFLOW JUG TO THE COLD MARK.DONT OVER FILL THE COOLANT RESERVOIR JUG.WORK SAFELY DONT GET SCALDED.

Thermostat might be your cause or a blown fuse maybe

SOUND LIKE ENGINE RUNNING HOT.MAKE SURE COOLING FAN TURNING ON. WHILE ENGINE IDLING WATCH TEMP GAUGE AS THE TEMP CLIMB COOLING FAN SUPPOSE TO TURN ON IF NOT.CHECK FAN FUSE AND RELAY. IF BOTH GOOD HOT WIRE IT. NO RUN REPLACE FAN MOTOR IF FAN MOTOR DO RUN. YOU COULD HAVE A FAULTY COOLANT TEMPERATURE SENSOR OR SHORT IN FAN CONNECTOR OR WIRES. CHECK COOLANT LEVEL.MAKE SURE YOU HAVE 50/50 MIXTURE OF WATER AND ANTIFREEZE.TO BE ON SAFE SIDE REPLACE THERMOSTAT AND PRESSURE CAP.

I had this problem with a 2007 Chevy Cobalt. I changed the coolant sensor and even though the check engine light went out I still had a reading of "---" on the coolant gauge. The problem is most likely one of three things: a low coolant level, a bad coolant sensor, or the thermostat needs to be replaced. The only other possible thing it could be is a bad BCM (Body Control Module) which in that case you would most likely be having other weird problems.

The Thermostat and the sensor are both very easy to get to and replace. Take off the engine cover by removing the oil cap and they are both to the rear of the engine on the driver's side. They are right next to each other.

Hope this helps!

did you replace the thermostat when you put the radiator in,you could still have an air pocket in the system,recheck your coolant in the radiator when it is cold.
the next thing is to verify the cooling fans are working,when you see it hot check to see if it really is hot or gauge is lying,if it is hot see if the fans are running to maintain cooling temp,if they are not check coolant fan fuse and relay and last fan motors

is the temp gauge sender new
or the engine cooling fans spinning fast enough
air in the heating pipes ? bleeding

If the replacement thermostat is good, and installed properly, then the temp sensor might be bad. I hate to tell you ($$$$$) but waterpump could be bad (more expensive)

Taking some of these things apart......

The temp gauge not registering a hot engine is a real bane on Zetec engines - check your coolant level before you do anything else. It may be that the system was airlocked when you filled it and that you got less coolant in than you thought you did.

It takes quite a short to blow a 50A fuse. First, make sure that the fan you've been looking at is actually the one protected by the fuse. Find out if there's anything else it protects. Check that all the fans/motors downstream of that fuse are free to turn (stalled fan motors are particularly good at blowing big fuses), and check all the cabling in between paying particular attention to places where wires pass close close the edges of parts that might chafe against them.

A.