I just replaced the thermostat and water pump and now weird stuff is happening, i just drove 15 minutes going between 95kmph and 60 kmph and it barley made it past the 50° mark but on the return trip it wasnt 3 minutes the car was up to temp, should this be of any concern to me?
assuming you didn't put the new thermostat in backwards, did you "burp" the system after replacing all of the coolant? Sounds like there is air in the line. I know some cars, like the Fit, can be a pain to get all the air out. It normally takes a couple of days of removing the cap and topping the coolant off until it is full.