Cant get rid of sweet smell

K so I bought two corny kegs from NB and cleaned them thoroughly, taking everything apart and letting it soak for over 24 hours. One was used right away and the other sat for a few weeks. I opened the one that sat last night and it still smelled really sweet. The caustic cleaner they use to remove soda is supposed also smell sweet like 7up. I cleaned it again with oxy last night and removed all rubber seals and poppets because I've heard they can retain smell and taste from soda. It had no smell after the cleaning it last night so I put the lid on (no seal) to keep dust out and today it smells sweet again.

I've looked inside and it's clean. With no rubber left the only thing it should smell like is clean metal. Should I be concerned? Obviously I don't want to get off flavors or smells in my beer. I'm thinking of filling with plain water and letting it sit for a week to see if the water pucks up anything.

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I had one that still had tons of residual sprite, or so it appeared. I soaked it in hot water with PBW for ~1 hour and rinsed. Smell was gone and kegged the beer right away. After each batch I repeat and never have had any residual smells/tastes left behind.

+1 to cleaning it with pbw. it's awesome stuff

Used PBW in the initial wash. I'll hit it again with PBW and hot water and see what happens.

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you need to get a dip tube brush and clean the insides of the dip tubes. baked on sprite wont wash out from inside it without scrubbing. i got one keg, used, with a sprite sticker still on it. i completely disassembled it, new o-rings, rinsed and soaked it in oxyclean over and over for a week- nothing. the smell only went away after i swabbed out the dip tubes.

did you use co2 to force pbw through the pipes?

I'll try that. But when it sat overnight last night I had both dip tubes out of it. It was only the empty shell with a lid on it. No seals, valves and dip tubes removed.

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Yep on forcing PBW and oxy through the pipes. I'll try to find a dip tube brush.

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since you have the tubes out already, fill the keg with oxyclean and water. put the tubes down into the water, and make sure they fill with cleaning solution. let it sit overnight. most important; make sure they fill with cleaning solution

I had the same problem. It ruined the first batch of beer I kegged (figured it'd be OK with just a rinse... I was wrong).

Anyhow, rinse with water; fill with water (preferably hot) and a scoop of oxyclean. Maybe use the discharge water from your wort chiller for hot water.

Anyhow, pressurize the keg(s), press the poppet valves down to spritz out some oxyclean (this will fill the tubes and valves from the inside) and let the thing sit for as long as you can. A couple days minimum, but no more than a month or so (you'll start to get crystals forming). Rinse, and you should be good.

At least that's what I've found to work to get rid of the acid odor.