Temp Spike Still

I changed my t-stat. Purged all the air out of the system. Still the same damn temp spike as before. So now I'm changing every damn sensor on the coolant system. But before I do let me know what you think. I know the temp spike is false because I opened the radiator cap after the guage went all the way up and stuck my finger in the coolant it was hot but not so hot that I couldnt stand it. I'm wondering if the radiator cap could be the culprit here. Thanks in advance. Tom