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Q: After parts replaced, bubbles in reservoir

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The repair shop replaced the thermostat, the water pump, and also bled the system. But I see bubbles in the reservoir and also there’s no water or smoke in the tail piece. It’s not a coffee color on the dip stick. The car doesn’t shake, so that might be the radiator. What do you think is causing these problems?

Hello. If all of the air is out of the system then the issue is internal. It is typically caused by a blown head gasket. This can occur when the leak is really small. When it is small enough the combustion pressure will enter the cooling system and cause this to occur without having any smoke from the exhaust. A block test can be done to identify the issue. If you want to have this test done, consider YourMechanic, as a certified mechanic can come to your home or office to inspect the issue.

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