I have a 1994 Mercury Grand Marquis LS and was having variances in the tempurature. I changed the thermostat but it didn't help. I took it to a mechanic and had him flush the heater core for $50 which seemed to help. They also suggested a whole system flush in the future for $89. Wouldn't the whole system flush have included flushing the heater core or are these two separate procedures. Also, by not getting the entire system flushed, am I risking recontaminating the heater core?
Thanks so much :-)