Q: No heat when ideling or driving slow.

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I changed water pump, thermostats ( mechanic said there was 2) , heating coil , bled air with vacuum service. No leak in head gasket. Top hose on radiator is hot and bottom hose is ice cold. The engine is not over heating.

My car has 90000 miles.
My car has an automatic transmission.

The lack of heat being generated by your system may indicate a clogged heater core. The [heater core]((https://www.yourmechanic.com/services/heater-is-not-working-inspection) is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. The other possibility is that the thermostat may not be allowing the engine to reach a normal operating temperature and since the engine’s warm coolant is the essential source of the heater core supplying heat to the inside of the vehicle, this can impact the warmth of the heat inside the vehicle. I would suggest having an expert from YourMechanic come to your location to diagnose your heating system.

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