Loud banging nois when compessor shuts down

Make sure the fridge is level back to front and left to right. Banging is normally the compressor shuddering on its rubber mounts, or the compressor is failing. Watch the unit from the rear as it shuts off. You may need to remove a cover held by a couple of screws.

https://www.google.com/search?q=Kenmore+20+porcelain+plus+banging

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2545 is a piston compessor if so you've got a busted rod on one of your cylinders , this will fail catastrofic and break out side of compessor but if caught early can still be rebuilt with a few new parts

Where is the noise coming from? The front, back, top, or bottom? Is it a bump, thump, bang, clang, or rattle? Does the sound happen at regular intervals or randomly? It could be the compressor bushings going bad, causing the compressor to bang around.

change the rubber isolating washers on the pump and compessor too hard a compound will make things worse ,neoprene works best ......

IT SOUNDS LIKE YOUR COMPRESSOR IS NOT UNLOADING WHEN IT SHUTS DOWN. YOU SHOULD HEAR AN AIR RELIEF SOUND TYPICALLY ON THE SIDE OF THE PRESSURE SWITCH WHEN IT SHUTS DOWN. ITS A SMALL VALVE WITH A TIRE VALVE THAT THE LEVER HITS AND RELIEVES THE PRESSURE FROM THE DISCHARGE LINE AND THE TOP OF THE PISTON.

YOUR CHECK VALVE COULD BE BAD LETTING PRESSURE BACK UP BUT IT WOULD BE BLOWING AIR OUT ALL THE TIME WHEN SHUT DOWN.

IF YOU THINK THE VALVE OR SWITCH IS WORKING AND WANT TO CHECK IT, LET THE COMPRESSOR BUILD UP AND SHUT DOWN, LISTEN FOR THE AIR RELIEF,IF IT DOESNT THEN CRACK THE DISCHARGE LINE AND SEE IF THERES ANY PRESSURE, MANUALLY RELIEVE THE PRESSURE THEN USE SOME AIR AND SEE WHAT HAPPENS. REPAIR VALVE ON THE SIDE OR CHANGE PRESSURE SWITCH $30-40.00. HOPE THIS HELPS. PLEASE REPLY. JODY

John,
What you are hearing is popping caused by thermal expansion inside the evaporator enclosure during its' defrost cycle.
Depending on your make and model, it'll go into defrost every 8 to 12 hours of compressor "run time". That is, the defrost timer "monitors" how long the compressor runs and after it accumulates the pre-set "run time", the timer then shuts the compressor off and initiates its' programmed defrost routine. This routine lasts for 20-30 minutes, or until the defrost thermostat opens.
The defrost routine sends 120 volts to a heating element in the evaporator compartment which gets red hot. This sudden temperature change (from below freezing to warm) causes the cabinet to expand slightly. That's when you hear the "Pop".

I hope this helps, John. Thanks for using FixYa, and don't forget to rate my answer.

SG

The compressor is that black casing you see at the bottom of your refrigerator - inside this sealed case is the motor assembly which stits on 3 or 4 springs that act like a cushion - you have a little gap at the bottom where the lubricating oil is present. Your springs have likely worn out and when the compressor shuts off the assembly is banging against the rigid casing make that loud "klonk" or bang noise. It IS normal for compressor to make some faint "tick-tick-tick...tick.....tick" when shutting off, but loud banging, bell sounds, etc, means the assembly is banging on the case from the inside - you can indeed live with the noise, your compressor will function normally, probably for months, or even years - it can also keep wearing out and one day the noise might get very loud (like a very high humming noise) - There is NOTHING that can be fixed, you either pay $400+ to change the compressor or buy a new refrigerator - If you DO replace a compressor usually the replacement will be noisier - Keep a thermostat inside your refrigerator at all time to make sure your compressor is still keeping your refrigerator and freezer cool.

it is compressor shutting off,not much you can do to fix it.you can try changing the snubbers that hold it in place but most likely you will still hear it clunk.

Check the compressor mounts. They are usually springs mounted with rubber. If they are two loose the compessor wil hit some other metal part when starting up. Shakle it and see what it is hitting. Ajust accordingly. 

if its a loud banging noise when the unit kicks off then broken spring in compressor will have to replace compressor check your 2-5th year warrenty in your owners manuel