1994 teg gsr 125k mi:

the other day i changed oil/filter, replaced plugs(with copper ngk's), checked wires, drained radiator(not block) and refilled, bled, etc. added some chevron injector cleaner and called it a night.

the next evening as i was driving home i glanced down and realized the temp gauge was as far into the red as it could get and overheated as i pulled into my driveway(sending coolant everywhere, i hate that sheit). After the car cooled i pulled off the radiator cap only to find it had broken and lodged itself in the neck of the radiator. Pulled it out, drained the radiator, and replaced the cap. Problem solved right? Nope, took her out for a test drive which went well just cruising around (50-60mph, shifting ~4k or so, being nice in general) but when i would get on the engine(WOT) the temp gauge began to climb rather quickly. Take the load off the engine, turn on the heater and it would drop back down but as soon as i put it back in gear and put a load on the engine it would climb again.

Whats the issue here? I didnt realize changing out coolant could cause a friggin cooling system break down. Only thing i can think of is that a chunk of the radiator cap made its way to the thermostat and caused it to malfunction in some way or coincidentally it just went out around the same time. Any other thoughts/suggestions would be appreciated. i am not very familiar with the ins and outs of the cooling system so any help is useful.

Thank you

Ryan