A spike and drop in a temp gauge does suggest air in the cooling system, there is a bleeder valve on the water pump for that, not the cap off the bottle.
However, your loss of heat is what worries me. That usually is a LIMG or head gasket issue. Are there air bubbles in you coolant? Does the car vomit coolant out of the tube on the bottle? More so after flooring it?
Do this.
Park on the street (mom and dad might get pissed if you do this in the driveway
) level surface, pop the hood while your waiting for the car to warm up. Watch the coolant bottle, quick revs in park, if the coolant stays in place, that's one HG leak you don't have. Then crack when hot (be careful) with a 7mm socket and spinner and see what comes out. Coolant should come out right away. If not, it's air, then coolant and see what color the coolant is.
Before you start the car, check the oil and smell the dipstick. People at work make fun of me for this, but sometimes and coolant isn't on the stick just yet, but the scent of coolant is. This happened with one of my LIMG leaks
