I have 92 sc400, the temperature has always been around the mid range mark but for some reason today, when I was stuck in traffic bumper to bumper the temperature was getting higher and higher almost to the red marker. But as soon as traffic ease up and I was able to pick up more speed the temperature drop back to mid range.

At first I thought my fan was not working, but as soon as I got home i popped the hood and the fan was working fine.

Any idea as to why the temperature went up sooo high?

 

Sounds like a stuck thermostat. I'd say replace it anyway, even if it seems ok.

 

stuck thermostat or semi-clogged radiator. Same thing happened to my 1jz sc

 

this happened to my girlfriends car. she had a clogged radiator. potentially u can flush it thoroughly and it will be fine but if its too far gone ur gonna need to change. and might as well change the thermostat while ur in there

 

put a BIG block of ice on the engine bay... that will solve the problem for good