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Q: Does a blocked heater core make the engine over heat

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I am getting no heat in the cabin and the heat Guage goes to the red zone then will drop back down and then rise again.I have replaced the thermostat but still have the same problem .so I'm wondering if the heater core is blocked or if I should replace the water pump

My car has 197000 miles.
My car has an automatic transmission.

Hi there, If you suspect the heater core has blockage then you may also have a radiator that is partly clogged up. You should have the cooling system diagnosed to see if the system is plugged up and needs components replaced. I have seen GM vehicles get gummed up from the use of incorrect coolant types or additives that interact with the engine components. The only way to know is to look at the coolant overflow reservoir and you will see a brown thick residue in the coolant. Have the system checked and overheating diagnosed by a mechanic.

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