Changing Oil Thermostat

[newsboy]

So, I was trying to change the oil thermostat. probably is original in 1990 964. Removed the circlip, expecting the spring to push the cap ou,. no luck. Tapped with a punch, to try to loosen. Sprayed with Kroil, then used a small air hammer with a broad face, no luck.
Applied some heat, more Kroil, still no luck. Imagine there is some galvanic corrosion going on. Ordered a new washer/disk for $30.00,
from Germany( none in the U.S.) Plan to drill and tap with a screw and try to pull it out. Out of curiosity,do you know of any other way?
Thanks

[Steve]

Nope, thats the right track.

These can be stubborn after this much time. Patience is your best friend (and sometimes heat).