Q: Car overheating. Around town it's fine. At highway speeds, heater stops blowing cold, and car overheats

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When I first start out, the car is fine. But once I get up to about 55-60 it starts getting hot and doesn't go back down. I replaced the thermostat last night. I thought it was that since the heater would blow hot then it would blow cold.

My car has 160000 miles.
My car has an automatic transmission.

When the heater starts to blow cold, it could be that the coolant level is low, or it could be that the coolant is boiling and the heater core is full of steam. If there is a leak in the system, and the coolant is low, you might have some air pockets that are preventing the coolant from circulating. You can check the coolant level at the radiator with the engine COLD. Looking at the radiator overflow tank won’t tell the whole story. If the system is full, you might have another problem, it could be as simple as a blocked radiator as bad as a leaking head gasket. for a diagnosis and some peace of mind you can contact Your Mechanic. They will send a technician to your home or office to check out your overheating Olds and let you know what can be done for it.

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