To the Doctor:
I just got my car serviced. Before, my heater was not coming on, but since they performed a radiator flush I'm getting some heat now. What could be the problem?

The Doc Says:
Usually when you have problems with your heater (especially one that is partially remedied by a coolant flush) you're talking about a problem with your heater core. Essentially, a heater core is like a radiator in reverse. Hot coolant from the engine is pumped through the heater core, and air blows over it to transfer the heat from the heater core to the car's passenger compartment.

However, sometimes the passages inside a heater core can become clogged with contaminants (especially if impure water was ever added to your coolant). This can keep the coolant from circulating and prevent your car's heater from warming up as it originally did. In addition, your heater core might leak, in which case you'll often notice a sweet smell inside the car or see a wet spot on the carpet.

You might try another coolant flush to see if it can loosen any more of the contaminants to restore your heater. You might also ask about coolant additives that can help clean the inside of your car's cooling system. If none of these work, or if your mechanic diagnoses that the heater core is leaking, our advice is to have it replaced. A leaking heater core can, in rare instances, suddenly burst and fill the inside of your car with hot coolant!

Hope this helps.

The advice described above is for informational purposes only. It cannot and should not be used in lieu of an actual, physical inspection and diagnosis by a trained mechanic or automotive technician. The opinions and advice offered herein are not intended to diagnose automotive problems or component failures; they are simply intended to provide information on what could be transpiring. VehicleMD accepts no liability resulting from actions taken as a result of this advice.