heating problem

[eminotaur]

greetings,

my heating has malfunction,
but when I go to the open road and drive fast (100km/h), after 5 minutes heating starts to work again but in city driving is not working.
I changed thermostat, water pump, poured cleaning liquid in Killer and again I am in the beginning, nothing happens ...
if someone has experience?

[DARK AGE 53]

if the problem started after the thermostat or water pump change it could air pockets in the system.