I have a lieebherr fridge freezer model ctnes4653 and i have noticed that ice is building up at the back of the fridge (before it used to drain down the back of the fridge and evaporate). i thought of switching off and defrosting completely. i have checked the drain hole but does not seem to be blocked. can anyone give me any other advice before i call in an engineer?

Have a look inside fridge compartment (especially the "roof", if it's a top-mount freezer) & see if you can see any ice build-up (look inside vents that allow cold air into fridge from freezer section. Also, if top-mount freezer, look inside the freezer compartment for ice build-up on "floor", inside vents, or on back wall. These symptoms, combined with water dripping from lots of the "roof" of fridge section (in a top-mount freezer model), can mean several different problems, so best to re-post with more info/symptoms included.
If there's no ice build-up (& the dividing area between fridge & freezer sections isn't particularly cold, which otherwise might indicate hidden ice build-up), it can be as simple as a plugged or obstructed drain tube, which is VERY COMMON. Easiest solution for this latter problem is to use a flexible plastic tube (think similar type as attached to aquarium air pumps), stuff it into drain hole, and blow on the other end. Sometimes you have to blow quite hard to clear an obstruction or complete blockage. If you can't clear the drain tube, it's likely a different problem. Again, a re-post with more info/symptoms will help narrow it down.

clean ice from drain hole then take a wire hanger and cut it to about 3-4 inches , wrap one end around defrost element anf the other end down the drain hole . use a turkey baster to force VERY hot water down drain hole to clear build up and debris

The problem is relatively simple to repair. The drain tube in the freezer is blocked so the water will drain down the back of your fridge. Often the drain gets blocked by ice build up. The defrost circuit in your fridge has failed and ice is building up on the evap coil in the freezer. When the ice builds up, it blocks the drain tube. The typical failures of the defrost is the timer failing to advance or the heater is burned out. Being that said it was probally manufactured at least10 years ago, and certainly a new refridgerator would be more energy efficient and cheaper to operate than using a 10 year old model. Whether you should repair or replace it depends on whether you have the money to replace it. Hope this helps you.

Clear ice build up from drain plug using hot water in a syringe. Works well I just did mine. Located behind access panel inside fridge. Blue tube running down the back. Pull down and remove ice from the drain at the top.

The defrost cycle is melting ice that will not go down the drain tube in the rear of the freezer. This can be a clogged tube due to debris, organic growths or ice blocking flow. What doesn't end up dripping into the fridge ends up freezing in the freezer compartment. Make sure the fridge is level or tilted back slightly.

Unplug the fridge from power. Remove the contents of the freezer and remove the ice maker, back wall plate and floor plate in the freezer section. Remove ice build up on the floor and tray in the freezer by thawing and soaking up water. Flush hot water (use a turkey baster to get at it) at the opening of the drain hose that is connected to the tray to thaw any ice.. once flowing to the evapraor tray under the fridge, mix up 1/2 oz of bleach and 4 oz of water and pour down the tube to kill any bacteria.

Reassemble and restock the freezer. Monitor the temperature of the fresh food (34 deg) and freezer (0 deg) compartments. If you notice the temperatures start to climb, there may be a problem with the defrost timer, terminator, etc. and may require a pro's help.

Good luck!

The drain heater goes into the drain,not outside it.
You need a longer drain probe to push all the way through the drain.
Look underneath for a kink in the drain tube.

Mine is doing the same thing

the defroster isn't close enough to the drain to be effective. remove the back wall of the inside of the freezer, remove the excess ice. clear out the ice from the drain using hot water and a turkey baster. there is a kit from whirlpool that uses a piece of metal and a screw around the defrost rod, but I found out that a piece of 14 gauge solid core wire with the insulation stripped off works great too. stick the stripped wire into the drain, 2 to 3 inches, and wrap the rest around the defrost rod.

the ice maker wont cycle untill the temp of the ice is around 10 degrees so if the freezer is at 15 or 20 due to some other malfunction then you will see the maker full of ice but it wont harvest and make another batch. so you could have a sensor bad, control malfunction, refrigeration issue, compressor, defrost system malfunction(you mentioned ice build up)

did you try to remove the 2 ***** in freezer floor???. if not remove the floor and check for ice build up underthere, if so:

you have a clogged defrost drain tube. removing back panel of freezer will give you acess to drain trough, melt away the ice with a hair dryer, youll find a drain hole under there somwhere,pouring boiling water down the drain will clear it pretty quickly( i use a steam machine purchased from the infomercials works awesome, after you clear it and all water drain down tube wrap a piece of solid copper wirearound the heater( black calrod heater right above the drain trough) and stick it in the whole maybe an inch or so. now everythime the heater comes on to defrost it will prevent the hole from freezing over