I have a 1994 sc400 and I noticed my Temp gauge started slowly going up to the 2nd to top line. I turned my car off for 15 secs and turned back on and it stayed at normal the rest of the day. Did it again yesterday while on the free way. I let go of the accelerator and it went back to normal. Any ideas of what it could be? No coolant leaks at all

 

make sure your not consuming coolant. If your a little low what you described could be caused by a bubble of hot air in the system. Or you have an intermittent short to ground on the sensor wire or loss of ground.