hey guys
yesterday after i shut off the engine i heard a sound sort of like a hydraulic humming or adjustment being made automatically. i have never heard this before or at least i never noticed. does anyone know what it could have been. the humming came in like 3 second intervals about 15 seconds apart.

 

From inside or outside?

 

It could be the Vacuum switch fo brake booster pump broken beside the air filter housing (orange connector) if it leaks or cracked can cause vacuum pump to cycle even after key is off.

 

Or could be ETM or also the incar temp sensor in the climate module.