where to start? This happens on the freeway on my way home from picking you my brother the temp needle flickers and goes dim and goes way up into the begining of the red zone. I made it home and it didn't go any higher. It just floated there. I popped the hood and let it cool. I haven't driven the car since. Where should I start checking for problems? The radiator is full of coolant or so the resviour. Could it be a sensor that faulted? Fuse? Do you think the theromstat needs to be replaced?

This is a 94 gs300..

 

was the resivour full of coolant and boiling? If so you overheated. If you drove in the red with it over heated you probibly blew a head gasket

 

Man dont really think you Blew your head gasket right out of the gate..
Check your Fan to see if the Fan-Cutch is tight or if it has been worn out over time and is easy to move. Also Let us know if it was boiling in the resivour Because it should have been with how hot you said it was.
When it was going into the red did it Get cold then hotter, cooler then hotter or did it just go straight to hot?
If it went straight from normal to hot you could have a frozen thermostat.
You can also get a Pressure leakdown test at your local shop to find out if the Head gasket has been Blown.
Have you replaced anything lately?

 

this same thing happened on my SC. turns out the radiator had a hole in it. BUT...the safe thing to do in this situation is buy what i bought. a fail safe thermostat that prevents overheating. just incase its that, or anything else your engine won't overheat anymore.