Hi,
This could be a couple of things. First, make sure the engine coolant is full. If low, there could be air on the heater core under the dash.
Next, pay attention to if it seems to only happen when the AC is used or the Defroster.
I'm assuming you hear it in the vehicle. If it is loud enough to record, do so and upload it for me to hear.
https://www.2carpros.com/articles/engine-coolant-59420607
I will watch for your reply.
Take care,
Joe
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Tuesday, April 26th, 2022 AT 7:54 PM