Q: Over heating coolant not siphoning back into coolant over flow tank

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About 2 weeks ago my car started to over heat as i was going on the highway. When i checked my coolant (after i let it cool made it home and let it cool completely) i noticed that the coolant overflow tank was completely empty but the radiator was over filled with coolant. Added more coolant to tank. Couple days later car wad over heating again opened hood and noticed the coolant was spilling out onto the ground because it was being spit outta the overflow port on the cap that goes to the coolant tank. Was told by one mechanic it was my thermostat. Had it replaced yesterday. Today care is still over heating and spitting coolant out of the overflow spout instead of siphoning back into coolant overflow tank.

My car has 250000 miles.
My car has an automatic transmission.

Hey there:

It’s common for many mechanics to make the mistake of mis-diagnosing the cause of an overheating situation; especially when they assume it’s a thermostat issue. The problem could be caused by a blockage in the coolant tubes running from the radiator to the overflow tank and back to the radiator. However, it also may be due to air trapped in the coolant lines. I think a good idea would be to contact a different ASE certified mechanic, such as one from YourMechanic, and have them complete a coolant flush, which should remove any blockages in the coolant tubes and may solve your problem.

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