Random over heat... thermostat?
 

Yesterday I drove about 2 miles then shut her down for approx 2 min, then I started her up and drove about 1/8 mile and it was in the red and I had a check gauges light. So I killed the motor and coasted to a stop, I put the key back on to check the temp and it had dropped a few degs but I knew I needed to limp it back around the corner to my house. well just after I started it back up the temp spiked back down to norm op temp. It kinda looked like a sticky thermostat... any Ideas.

Re: Random over heat... thermostat?
 

Have you checked the coolant level in the radiator?

Re: Random over heat... thermostat?
 

the coolant was full, as a couple weeks ago I r2 the opti and replaced all the coolant and properly bled it.

I know it was really over heating and not just a sensor cause the overflow was boiling and I had to add water to the res tank this morning

Re: Random over heat... thermostat?
 

Just for fun, look in the radiator when the engine is cold.

Re: Random over heat... thermostat?
 

ok so for S&G I checked the radiator, it is full to the top.
As I said I heard it going into the overflow when it was overheating. I figured the radiator had pushed out the water in the overflow and when it cooled off it sucked all back in and gave me the low coolant light this morning. I refilled the overflow this morning, and since yesterday that one time It never goes above op temp. And I checked the Overflow and its still full.(no bad head gasket..) :)
the only thing I can think of is maybe there was air in the system that some how cavitated the pump. Or the t-stat got stuck closed(why it over heated) then popped open, (why the temp shot back down so fast as the cool water got through)

I cant think of any other reasons for the random spike.