Gauges acting weird

[BiXLL]

This is Ag21 using my dad's computer. I have been driving my 93' 240sx and lately it has been acting weird. After about 20 minutes the engine temp gauge will start to steadily raise and in about 3 minutes it will go past the maximum and the indicator will be past all of the lines. Then it will go right back down. If anyone knows what the problem could be or how to fix it would be greatly appreciated to here your responses.

[-RJ-]

i remember mine doing that when i had a blown head gasket. does it go down when you take a turn?

[BiXLL]

i remember mine doing that when i had a blown head gasket. does it go down when you take a turn?

No, I pull over and wait a few min. and it goes down, really strange?????

[biggie]

Most likely the thermostat is bad, need to replace it.

It's getting stuck closed, temp rises and then it finally opens. But needs to be addressed soon, otherwise will blow the HG.