[elmariachi]

So you are saying either:

1. The 10-12 ounces of coolant that is leaving your system (and now going in that plastic bottle) is enough to make your temperatures fluctuate to such erratic levels; or

2. You had more air in the system that needed to be burped out; or

3. You needed more radiator cap; or

4. Some combination of the above.

I am surprised anything can get past that 20 lb cap, but maybe that's common for that engine platform.