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Q: Overheating for no apparent reason suddenly and after a longer drive

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My car that has around 150,000 miles on it keeps overheating for no apparent reason. It suddenly starts showing that it reached the hot zone when I just start driving. When it happened a couple of times, my AC used to blow hot air instead of cold. Now it blows cold when it is overheated.

I've had all kinds of testing, from coolant checking to bleeding the coolant system, replacing the radiator cap, changing the thermostat. Also, the water pump was replaced. After that, while driving around town, it ran great so I decided to go to a longer trip. Then it started overheating again. It happened after about 25 miles of driving to the point that it couldn't be driven anymore. Please give me some advice on what to check next.

Hi there. It sounds like you may have a blown head gasket. This is typically the only thing that will allow the engine to overheat that fast. When the gaskets begin to leak, it will allow combustion pressure to enter the cooling system causing this to overheat. I typically start by doing a block test to see if there is any exhaust gases getting into the cooling system. I will also use a 5 gas analyzer if the block test does not show anything positive. If the head gasket is fine, then I would suspect that there is some blockage in the radiator that may need to be replaced. If you want to have a certified mechanic verify the faulty component, a technician from YourMechanic can come to your home or office to diagnose your car’s overheating problem and perform needed repairs.

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