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New head gasket bubbles in overflow when turned off


mlunsford

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I had leaking head gaskets. I took the heads to be checked and rebuilt which are the aftermarket ones . Used the heavy duty head gasket felpro set and new bolts. Put all back together . After one week I checked and no bubbles in overflow while engine is running. But when engine is turned off I will get a few bubbles in the overflow tank. Not over heating . I am wondering if the head gaskets did not seal?

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RonD

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Answered in other thread, do glove test, if no cylinder to cooling system leaks then you need to get all the air out of the cooling system when refilling.
remove 1 heater hose while filling, that will get most of the air out.
 

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enjr44

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Bubbles into the the cooling system overflow tank are normal if the system is not completely full and working normally. If the radiator cap is good, the overflow line to the overflow tank is good, the pickup tube (if there is one) is there and there is coolant in the tank each heat cycle of the engine will draw coolant out of the overflow tank and back into the radiator as the engine cools.

As the engine warms the coolant expands and forces either coolant or air out of the top of the radiator and into the overflow tank. In the days of old there was no overflow tank, that excess went onto the ground (bad) and the radiator was never completely full when cold (owner's manuals used say the system was full when coolant was around an inch from the top). For a few minutes after you shut down the engine the coolant gets warmer and expands some more (more bubbles?). As the engine cools fluid (if the pickup tube is submerged in coolant) is drawn back into radiator.

So if there is no over heating and with each heat cycle there is less coolant in the overflow tank (indicating the system is working correctly) and you keep topping up the coolant in the tank, it will fix itself over some period of time.

You can speed it up by manually filling the radiator to the top each time the engine completely cools.
 

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