My Lg bottom freezer refrigerator, model # LFC21770ST leaks constantly down in the bottom of the freezer and comes out onto the floor. Ice dams build up under the freezer drawer. I take out the ice, but it keeps leaking and building up. Seal looks fine.

It sounds like the defroster is not working. Look up online for solutions that are posted.

Is there a water leak?

Is this auto-defrost model? Usually, heating element that defrosts the ice in back of freezer can go bad. How old is the model?

you have a blocked drain in the freezer,when the machine goes into defrost the heater comes on and melts the frost off of the evaporator coil,the water melts and goes down the drain hose under the coil and leaks down to a drip pan near the compressor where it evaporates from the heat,your drain is blocked and the water is leaking onto the freezer floor and will drip out onto the floor,i use a steemer to blow out the drain line,shut down the machine or unplug it,melt out all the ice with hair dryer,depending on your model you might have to remove the back inside wall of the freezer to get at drain hole,you need something to push the **** out the drain hose,you can try a turkey baster or air from a compressor or a shop vac set it to blow,when you think it's clear pour a cup of hot water into the drain,if it drains down you're done if not keep hitting it with heat and air to push it through.

Typically on this model the drain hole Under the evaporator cover gets clogged. Remove the cover off the rear of the refrigerator and pour hot water into the drain until it goes down quickly. To remove the cover u will have to remove all the freezer shelves and the icemaker. Remove the covers screw and u should see that at the bottom u will have a block of ice down below. The refer goes onto defrost every couple days and will leak the melted ice onto the floor

http://www.youtube.com/watch?v=f8EmTaKNhas

check that both cyclic defrost elements are working i dont think they are

Your problem is possibly one of two things. The ice maker is leaking or the defrost tray behind the rear panel inside freezer back wall is clogged with ice or something else. If you know its not the ice maker unplug the refrigerator and remove the back panel to see if the drain is blocked there, Let me know, Sea Breeze

unplug it again , sounds like your drain line has frozen, instaead of defrost water going down the tube and under refrig in drain pan, becuse tube is frozen its draining into freezer compartment and eventually spilling out through front of unit. totally defrost unit and behind back wall of freezer youll see a metal trough designed to catch water, in the center (under the ice is gonna be the drain hole, pour boiling water down until it runs freely

Does it do it all the time or only when the ice maker call for water... you may have a bad water valve 67006531 VALVE, DUAL WATER or a ice dam in you icemaker let me know