I noticed a few weeks ago the heat was getting cool, i had the coolant flushes last year and the heat was fine, i'm in Ma so its starting to get cold here and the heat is like luke warm, i had my mechanic blow out the heater core thinking it was blocked up and it stayed hot for like a week now its getting cool again... anyone have this problem or is the heater core just junk in the car btw 125k on this 02 wrx.