Just did a coolant flush because Monty was blowing hot air on driver side and cool air on passenger side. I took it to get a coolant flush and gunk came out but the heat did not improve but it slightly did on one vent on the passenger side but not the one close to the window. I think I can survive since the front driver's side blows way hotter to make the car warmer. The issue I am having after the flush I drove home and when I got home I got out and checked the coolant level on reservoir and it was empty. Is this normal? Should I wait for the Monty to cool down and the coolant would flow back or I need to top up?