There is a bulge on the back of my SMEG FAB28RO fridge. It is soft, like a bubble (see pic). Also the internal wall is a bit bulged. The fridge does not cool properly. The freezer is ok, the rest of the fridge is not very cold.

It is a nice fridge so I'd like to try to repair it. Any ideas on how to troubleshoot/fix this?

Update: As suggested by @fraxinus, I have tried poking a small hole in the bulge, and I definetly heard and smelled refrigerant gas, so there must be a leak.


His majesty the fridge

Final update: After establishing that there was a leak (almost impossible to repair) in the refrigeration system, I decided to declare the fridge as deceased and do an autopsy, for the sake of science. Here's what's under the bubble:

The leak


As you can see, there's a rip in the insulation, and I don't think it is worth to try to fix it.

  • What is the metal that has the rip? Insulation should be pretty easy to replace. That insulation is thick did you drill more than 4" into the back of the fridge when you think you heard/smelt the coolant? Dec 10, 2022 at 21:55
  • Nice to see an update and the pictures, was it just the insulation that was causing the bulge? Was there a bubble inside the insulation? Dec 10, 2022 at 21:56

6 Answers 6


How to troubleshoot:

Get a needle and make a small hole in the bulge on the back.

You will get either nothing (the bulge will stay the same), or refrigerant (the refrigerant itself has no or almost no smell, you may or may not not sense the smell of the compressor oil, but the bulge will soften), or water.

Be assured that puncturing a single small hole will not make things worse.

Nothing = the problem is elsewhere. It may even be this way from the factory (some extra foam injected in this place). Refrigerant gas = refrigerant leak. Water = condensed water leaked in a pocket.

Contrary to the other answers, a lot of modern fridges do have a lot of gear hidden in the back. The usual suspect for a single-compressor fridge + freezer is a heat exchanger for the lower part. If there is a refrigerant leak, this is unfixable at a cost comparable to a new fridge. As far as I remember, this particular model was available at least in 2021 and maybe even right now.

It was not stunningly expensive either.

Water = some low-pressure tubing for condensed water gone bad. Fixable with moderate skills and some swearing. On the other hand, this does not explain the bad cooling. It may be the thermostat (only the lower part temperature is regulated). Or, the thermostat may be ok and just set too high.

Good luck fixing it. My wife wanted the same model but we considered it way too small for our needs.

Edit: since the refrigerant leak is confirmed, this is (roughly) how it could be fixed:

  1. Disassemble it from the back.

This requires removing the glued cover and the injected foam (be ready for an incredible mess).

If you find the approximate location of the leak in the process, good.

  1. (failing to spot the leak) find the leak using soapy water, refrigerant detector, by ears or otherwise.

  2. Get a replacement of the leaky detail. Good if it is a tube, good if it is some copper alloy.

  3. Cut the tubing at the appropriate places, replace the leaky detail, weld / solder it in place, attach it wherever it belongs.

  4. Vacuum the system, check for leaks, refill with the proper refrigerant (and compressor oil), check for leaks again, check for proper operation while everything is open.

  5. Get polyurethane foam and fill the voids back approximately to the previous state.

  6. While the foam is still not set, put the back cover in place.

Caveat 1: in most of the developed world, one needs to be certified in order to deal with refrigerants.

Caveat 2: refrigerants for small cooling devices (e.g. fridges) are different from the ones used in A/C units. It may prove hard to obtain the refrigerant or hire a competent technician, because small devices are quite rarely refilled. People tend to disassemble/refill or even build fridges only in rather expensive contexts - e.g. fridges for yachts or motorhomes.

  • 1
    I made the hole and I definetly heard and smelled refrigerant gas. So is it really unfixable?
    – Tropilio
    Dec 9, 2022 at 12:43
  • 7
    fraxinus didn't say it wouldn't be fixable, just unfixable at a cost comparable to a new fridge.
    – spuck
    Dec 9, 2022 at 16:13
  • 1
    Well, this is how to fix it: (adding to the answer)
    – fraxinus
    Dec 9, 2022 at 16:35
  • 2
    if it is leaking refrigerant gas I'd expect it to not work at all very shortly, is that the case? I have a hard time imagining that the bulge was actually holding the refrigerant gas. Generally if the refrigerant is leaking out it all goes out in quick order. Dec 9, 2022 at 17:53
  • 1
    @FreshCodemonger Al tubing is especially sneaky in this regard. Can leak for few weeks and one can neither detect (and fix) the leak nor use the device normally.
    – fraxinus
    Dec 10, 2022 at 22:30

I'd guess that water from defrosting is going places where it should not, making the bubble and bulge.

Might have a clogged drain.

Might have vents plugged with frost/ice so the cold from the freezer does not get to the rest of the fridge properly.

Often the best first step is to store your refrigerated and frozen food in a working fridge/freezer (friends, neighbors, relations...) and defrost yours for 24 hours or more with the doors open, perhaps with a fan blowing on it

Resist the urge to use heat guns or sharp things to "make it go faster." Those are more likely to damage it permanently.

  • The fridge has been defrosted, it was actually not being used, I just plugged it in today after months that it has been switched off.
    – Tropilio
    Dec 9, 2022 at 1:36
  • 1
    Also, the bubble feels like air/gas, I doubt it is a water bubble. This worries me a bit, I am afraid there is a leak in the cooling pipes.
    – Tropilio
    Dec 9, 2022 at 2:27
  • @Tropilio A refrigerator's compressor usually operates at just one speed so all the cooling happens in the freezer. When needed the fridge will open a gate to exchange warm fridge air with cold freezer air until the desired fridge temp is reached. So the fact that the freezer works fine tells me that you don't have a freon leak.
    – MonkeyZeus
    Dec 9, 2022 at 13:35
  • @MonkeyZeus Please read my comment on fraxinus answer.
    – Tropilio
    Dec 9, 2022 at 13:54
  • 2
    @Tropilio Important information should be edited into your question, not lost in a sea of comments. Comments are second-class citizens on this site and can be removed at any time for just about any reason.
    – MonkeyZeus
    Dec 9, 2022 at 14:09

That stuff is isobutane. It's flammable.

methane... propane... butane... pentane... octane (gas)... cetane (diesel).

The refrigerant there is isobutane. Propane is 3 carbons, butane is 4 carbons, isobutane is a "tee" structure. But it is flammable like propane, with a tendency to sink to low places. Keep the area well-ventilated.

Regulatory agencies who approve flammable refrigerants in consumer products generally require the amount of refrigerant be kept as low as possible.

I would consult with the manufacturer about repairability.

If this was a $600 Kenmore made in Korea, I'd say off to the recycling it goes. However this is a fancy/bespoke European unit with a fancy price tag, and also not particularly old. I would consult the manufacturer about whether the unit is field-repairable and to what degree they support that. On their advice, I'd then take it to a refrigeration repair shop. Of course those guys exist; refrigeration units in grocery stores use condensers on the building roof, and exotica like Coke Freestyle machines are too costly to just throw away over a Freon leak.

Isobutane is be OK to vent

Countries have similar rules because they all committed to them in the Kyoto Protocols, so I'm not being nationalistic to go with what I know: the EPA. For most refrigerants, licensed professionals must use recovery equipment to recover refrigerants and send them up their supply chain for recycling or reuse (the only source of R12 and R22 at this point).

They say non-qualified DIYers can only mess with (and vent) certain refrigerants considered to have nil ozone-layer effect and low global-warming effect.

Propane and isobutane are on EPA's "DIY friendly" list.

By the way, DIY heat pumps like Mr.Cool and Pioneer evade the "DIYers handling refrigerant" issue by having the DIYer not handle refrigerant, via clever designs: self-sealing couplers, or you build and leak-test the system using inert nitrogen.

  • 2
    Cyclopentane is not a refrigerant. It is a foam blowing gas. The fridge in question probably uses R600(a) or R134a like most modern-ish European fridges do.
    – fraxinus
    Dec 10, 2022 at 10:13
  • @fraxinus According to the manual, it's R600a in this case (isobutane)
    – Dan Mašek
    Dec 10, 2022 at 20:23
  • 1
    @DanMašek Then flammable, it is
    – fraxinus
    Dec 10, 2022 at 21:34
  • 1
    @fraxinus yeah, I should've seen that coming. An old buddy worked for Dart Container (who always used pentane; never any CFCs). Though, Wikipedia says it's a refrigerant too. Boiling point seems a little off honestly. Dec 11, 2022 at 1:19

The fridge back is generally very thin metal, since nothing comes in contact with it during normal operation. There's also nothing complicated going on in the middle of most modern refrigerators; as you've seen, the operating mechanism generally lives in the base of the machine. If there was damage to the cooling lines running up to the freezer I would expect other symptoms. So I would expect that this bulge/dent is unrelated to your cooling problem and just happened when the machine was being moved and bumped against something... but that's a semi-uninformed opinion.

If the freezer is cold but the rest isn't, that suggests you have an airflow problem between the two compartments. Sometimes that's just ice and a full defrosting solves the problem at least temporarily. Occasionally it can be a matter of something in the freezer blocking the vent; reorganizing the contents would solve that. So I'd start by moving the frozen foods into a cooler, defrosting completely, turn it back on and see if that solved the problem.

How old is this machine? If it's more than a decade, efficiency improvements may make replacing it worth considering even if you can restore normal operation.

  • 1
    The fridge has been defrosted, it was actually not being used, I just plugged it in today after months that it has been switched off. The machine is at least 10 years old, but it is a really good model (italian brand) so I'd like to try and fix it.
    – Tropilio
    Dec 9, 2022 at 1:36
  • 1
    If you just plugged it in today, did you actually give it time to fully cool down?
    – keshlam
    Dec 9, 2022 at 1:44
  • 1
    It has been plugged for all the afternoon. I have put a glass of water in the freezer and it turned into ice in about 1 hour, I have also put a glass of water in the fridge and it is not very cold. I will leave it on all night and check again tomorrow morning, but I think the fridge is not cooling properly.
    – Tropilio
    Dec 9, 2022 at 2:22
  • Minor note: Metal fridge backs is a safety requirement only in North America, European fridge backs can be plastic, as shown here. This was drawn to people's attention after the Grenfell Tower disaster.
    – user71659
    Dec 9, 2022 at 19:31
  • @user71659 but of course Grenfell only became famous because that fire spread via the building's cladding - the plastic foam insulating panels whose fire safety had been grossly misrepresented. Dec 9, 2022 at 20:43

What year was the fridge made? That looks like the old school ones that kids would hide in and not be able to get back out of. Cool color though !

Generally, if the freezer is cold and the fridge isn't, in a modern freezer up/fridge down there are two possibilities.

  1. Defrost timer isn't working, frost builds up in the freezer and prevents the fan from turning and pushing cold air into the fridge.
  2. The defrost drain is blocked, the water from the defrost cycle had built up and turned into ice and is either blocking the vent or preventing the fan from going.

Take all the stuff out of the freezer section, remove the back panel, you should see a fan and some metal fins (the defroster). You should not see very much if any ice.

If you see ice then either 1 or 2 are the problem. You can either use a hair dryer or a heat gun. I've used both. I've also melted plastic parts in the fridge by keeping the heat gun on the plastic pieces too long. If you have the hair dryer routine plan for a full hour of just holding the hair dryer against the ice.

Heat guns are cheap. I bought one just for this having done it at least 3 times. I tossed one fridge after the defrost timer went for the 3rd time.

freezer panel removed

  • I don't know the exact year, but it is not that old. SMEG it's an italian company that is famous for making 50's style stuff, but this fridge is definetly not from the fifties. I think it is 10 or 15 years old.
    – Tropilio
    Dec 9, 2022 at 2:24
  • What do you mean "remove the back panel"? I don't think it is removable.
    – Tropilio
    Dec 9, 2022 at 2:25
  • Inside the back of the freezer is typically a plastic panel that can be removed and once removed you can see the fan, access the defrost drain, etc. Dec 9, 2022 at 2:26
  • 1
    SMEG makes these 1950-style fridges even now (or at least did so back in 2021 when I looked to replace my broken fridge). And no, it doesn't lock kids inside, the impressive handle does nothing.
    – fraxinus
    Dec 9, 2022 at 10:44
  • @FreshCodemonger In this fridge there isn't a panel like the one in the picture you posted.
    – Tropilio
    Dec 9, 2022 at 12:07

It seems there's nothing wrong with your fridge.

I would guess it is just a cosmetic delimitation of the rear cover.

That can occur if they're cooling or hot part of the coil is near by.

As for your theory it might be a coolant leak you should see a puddle at the bottom of the fridge near the compressor. Also if you had a coolant loos the freezer would be the first one to know.

You say the fridge is not cooling properly? Is there a temperature gauge or do you have one to put it in. That problem (if any) could have different reason for not working properly.

  • Why a puddle? Isn't the coolant a gas? And actually yes, there might have been a puddle, because there is a lot of rust near the compressor.
    – Tropilio
    Dec 9, 2022 at 8:29
  • "delimination"? Delamination...
    – Solar Mike
    Dec 9, 2022 at 11:38
  • @Tropilio it is actually liquid till the compressor makes it into gas
    – Traveler
    Dec 9, 2022 at 22:57

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