hey guys my dad asked me to post and ask if you all had any idea why his truck would not be heating up very fast. he has replaced the thermostat but its still not heating up fast or even that much. thanks for any ideas. its cold here right now lol, brr ice everywhere

 

Try reverse flushing the heater core (and while your at it, flushing the block, lines, and radiator is a good idea).
Than refill with 50% coolant, 50% distilled water. (Distilled water because it doesn't contain minerals that aren't good for the system).