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Q: My car coolant level goes down even external no leakage found. Second it mileage only 10 kmpl on high way with new spark plugs.

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My car coolant level goes down even external no leakage found. Second it mileage only 10 kmpl on high way with new spark plugs. Third when I apply hard brake then pedal vibrate up and down and brake the car slow.

My car has 200000 miles.
My car has an automatic transmission.

If you are losing coolant with no external leak then the head gasket is most likely leaking. The fuel mileage will suffer if you have coolant leaking in one of the cylinders. The brakes will vibrate once the rotors are warped which calls for a replacement. If you decide to get this fixed, consider YourMechanic, as a certified technician can help you pinpoint your coolant leak and make the repairs that are needed.

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