Noise from expansion tank

[MQ2596]

Hey all,

A bit of background about this issue. I could hear a bubbling noise through the dashboard which a Merc specialist suggested could be air trapped in the system. They investigated the fault and checked all the systems and they said everything is working as it should be. They flushed the system out. No overheating issues and no leaking coolant. The bubbling noise still occurs and their position was that they could investigate further but it would cost more money, as they said the car is operating as it should be, they suggested further investigation would be a waste of money. The other day after I shut the engine off I could hear this from the coolant expansion tank… any ideas? Not sure if this is the noise I was hearing through the dashboard. I’m not sure what I can do because the specialists said the car runs as it should be. Is it a case of putting up with this noise? I could see some dried coolant on the expansion tank so I’m not sure if that could be coolant leaking out through the expansion tank cap? Thanks in advance.


Coolant expansion tank noise:

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[Martin 1]

What I can hear, sounds like, either there's a small split in the header tank, or the cap seal is failing, neither is expensive to fix. Try tightening the tank cap, if no good, replace it, , no good again ? replace the tank. Good luck.