If the previous cooler didn't have paste, it used a thermal pad....that pad was solid and room temp and then turned to goo the 1st time ya turned it on. So yes, wipe it clean w/ 99% isoprophyl alcohol.
wipe with alcohol rag/wipe, air dry, apply new thermal paste, spread evenly with credit card.
(learned the hard way)
Sorry for late reply, um...I can't remember exactly what it was, I think it was something with the thermal paste I forgot to remove in the past on one of my first builds I ever did. It got mixed in with the new paste and got too hot.
And to revise the method I posted above:
The pea sized amount of thermal paste in middle of CPU is the best method. I've tried them all.
CPU: pea size in middle
GPU: evenly spread not too thin, and not to thick layer while wearing a glove. Then use credit card/paper to spread it evenly.
Pea method is best on CPU's since the cores are all in the middle on modern CPU's.
I found with GPU the spread method gives lower temps. I'm still looking into this to confirm. If you don't know how to do the spread method properly, just use the same method as a CPU with a little bit in the middle.