Started this thread on m.net the other day when my car out of the blue started overheating gradually. I know it annoying to link to another thread but I was wanting some of you all's opinions on the issue.

Please read this and comment: http://forum.miata.net/vb/showthread.php?t=265638

 

Pull your spark plugs tomorrow and see what they look like. If one of them is cleaner or whiter than the others you could have a blown headgasket.

 

it still sounds like you have an issue....either the sender to the dash is failing (doubtful) or you have a headgasket issue.

since it's still spiking, it should never go past 12° o clock (especially with fans running 100%), i have a feeling it's the gasket. check your coolant level again to see if it's lowered.

 

I'll have to check them tomarrow.....what would cause that?