[Lukas111]

Hi,
I have heating issue with my 2004 grand prix.
I changed engine month or so ago.
My car is heating very slowly, If I drive on fwy it will not heat properly at all, temp gauge will be about 1/4 or bit over.
If I drive in city, temp gauge will go close to 1/2 and over if I stop on red light. So it is not constant and vary a lot.
It does not loosing coolant. I assumed it was thermostat so I changed it but car seems to be doing the same thing.
water pump is not that old, i took it over from my old engine and it had about 20k miles on it or less.
Any other idea what it could be?
My mechanic told me that if there is no engine light car is running properly.
Asked me for $50 t replace thermostat so I decided not to deal with him anymore, I did it by myself.

Interesting thing was that I tried to bleed system and I release bleeding valve at working temperature and I get nothing out, not air or coolant. Hose was pretty hot.