When you start the car in the AM there is a strange knocking/clicking sound. It sounds like someone knocking on a window. It coming from under the dash on drivers side. It lasts about 10 to 15 seconds. Everything in the car seems to work fine.If you leave the car off for several hours it will do it again.
Have you checked the oil?
+1
However, another–far less serious–scenario also comes to mind.
If a “blend door” in the car’s HVAC system is malfunctioning, it would definitely sound like a knocking sound, emanating from under the dash for a short period of time. Of course, this would be much more likely to be originating from the passenger side of the dash, but…
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Very good point,.
To test this possibility, cycle the HVAC controls, heat on/off, cold to hot to cold, defrost on/off, AC outside/recirculate/max. You might hear it then.