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Q: Truck starts to overheat and blows cool from the heater but fixes itself after hitting a bump.

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Truck heater will start blowing cold and temp gauge starts to rise. I pull the truck over let it cool off and start to drive again. It will start to heat up again and will hit a bump in the road as I'm pulling over and heater starts working again and gage drops back to normal. I have already replaced the thermostat it was broke in half according to mechanic. Truck drove fine for about 4 hours after thermostat was replaced, parked it for the night and then it repeated the same over heating problems the next day.

My car has 219875 miles.
My car has an automatic transmission.

The overheating may also be caused by other issues such as a bad heater core. This is a small radiator used to warm up the interior of the vehicle making the heater operational. A valve controls the flow of hot coolant through the heater core warming up the air inside of the vehicle.

When the cooling system is over worked in other areas for other reasons, the heater core tends to make up for this slightly by removing heat from the cooling system. At a certain point when the heater core can no longer do it’s job and remove excess heat, the car will begin to overheat.

To avoid any unnecessary repairs, I would recommend having an expert from YourMechanic come to your home to take a look at your truck to diagnose your cooling system.

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