More then likely you have a restriction or a leak in the heater core. Or less likely you have an air pocket in the heater core.
Here is a guide that will help with this:
https://www.2carpros.com/articles/vehicle-bubbling-noise
As for the engine bay being too hot but no overheating, we need confirm the temp of the engine bay because this is a little too subjective. If there is no issue with overheating then the engine bay may feel hotter then normal but this in and of itself is not an issue.
Let's run through that guide and go from there. Thanks
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Wednesday, October 7th, 2020 AT 8:35 AM