Dr4gonSoldier
I got a EVGA RTX 3070 XC3 Black Gaming 8GB (not Ultra edition), 1 yeah of use, I open the GPU to change the pads and thermal paste, now my GPU is going up 78-82c playing game use 99%, 100% of GPU.

I used thermal pad Gelid Gp-ultimate 2.0mm ( 15 w/mk )
And
Termal Paste Thermal Grizzly Kryonaut Extreme 2g ( 14.2 w/mk )
So why my GPU is taking alot temperature? Before I open and clean it, max temp is 65-68c playing games use 99%-100%.
 
Did I use the wrong size of thermal pad? 
 
btw sorry my bad english.

Welcome to the EVGA Forums
 
The thermal pads need to be the correct thickness & softness, so they compress as designed. 

You could email EVGA support for the correct pad size or to inquire about buying a set of "stock pads"
 
Your not the first person to get higher temps than stock on a 30 series GPU .... assembly & parts is critical
 

With the GPU die temps being higher than stock: (my guess would be)
 
1) TIM application - not covering the entire die
 
2) Heatsink is not sitting flat on the GPU die
 
3) pads you used were too thick or too hard & this increased gap (space) between heatsink & GPU
 
4) Room temp is warmer than before or you PC's fan(s) have different setting ?
 

Your new to the EVGA forums, so maybe tell us about your PC experience level with working on changing TIM & pads or building a PC