A while ago I bought an Audi A3 2001 8L1 and the temperature never reached 90°C, well it did (for a few minutes) but only when there was a lot of strain on the engine like going uphill but never on the highway at 130KM/H. So I thought the thermostat is bad and is always in open position. So, I replaced it with a quality one and the problem went away. However, right after I changed it and refilled the coolant I went for a 20 minute drive and noticed the temperature went above 90°C for a very short period of time and then suddenly dropped back to 90°C and stayed there, so I though there was probably some air in the cooling system.
I just recently went on a highway for about an hour, always driving at 130KM/H and the temperature stayed at 90°C, now here comes the interesting part, when I finished my trip and went off the highway (driving at 50KM/H) my engine started to overheat and went all the way to 115°C but normalized to 90°C after a while. So my question is, WHAT THE HELL IS GOING ON?
I would bleed the cooling system but as far as I know it can't be done on my car and according to some online sources it should bleed itself. Amusing that it should, where is the problem? Any ideas?
I should also say that the temperature with the old thermostat also varied from time to time even after the car had been driven for more then 30 minutes. It varied between 60-80°C.