Voltage not my temperature problem?

[roaddoc326]

So I started overclocking my i5 2500k and I was getting temps too high, so I lowered voltage to ~1.25V, but I am still exceeding 80C within the first half hour, what else could be the problem for such high temps?

On a second note how do I know when my voltage is too low?

Thanks.

 

[C12Friedman]

Possibly too much clock for the CPU or seating issue with heatsink or need better heatsink or too much/too little thermal compound or need better airflow - all are possibilities. You'll know when your voltage is too low when you become unstable

 

[drums101]

^^ this man is correct he pretty much hit all the possibilities

 

[roaddoc326]

Best answer selected by roaddoc326.