See also:

Lubrication oil circulation in the refrigerant circuit
Operate the air conditioner compressor at a low engine speed (at idle or low driving speeds) a few minutes each month during the off-season to circulate its oil. ...

Cooling system
Never attempt to remove the radiator cap until the engine has been shut off and has cooled down completely. Since the coolant is under pressure, you may suffer serious burns from a spray ...

General information
Noise from under the vehicle NOTE You may hear a noise from under the vehicle approximately 5 hours after the engine is turned off. However, this does not indicate a malfunction. This noise ...