START UP KNOCK

[XWrench3]

my liberty has a new noise. its intermittent, and only after the vehicle has completely cooled off. it sounds like a deep moaning knock, on the passenger side. it sounds like a dry bushing type of bearing that is both knocking and vibrating and moaning like there is enough play to allow the shaft (of whatever it is) to make an awful sound. if the starter motor was on that side, i would be yanking it out to inspect and **** the gear and bushings. i have had my wife start the car while i had a mechanics stethoscope on the starter motor, and it sounded ok, but it also didn't make the noise when she started it. the only other thing i can think of, is the previous owner replaced the A/C pump. he said he did it himself with the help of his dad. i have always wondered if they put oil in the new pump, or added it at filling. any idea how long a pump would run if there was no oil in the system? i also don't know if oil remains in the system when you open it up to replace parts (i understand the basic operation of A/C, but i have never worked on one (other than to add Freon to see if it would restore the system. any other ideas? its not something inside of the engine. it is something on the outside. things like this are fairly easy to find when it happens all the time. but i don't want to wait until there is a foot of snow on the ground.

 

[Billwill]

Pull out the AC Relay to stop the AC Clutch engaging and see if noise is gone....check that the AC is not in fact rotating..the AC Clutch can jam up solid.

Or the Serpentine belt on its pulleys, Alternator bearings?