I would dismantle them and replace all of the o-rings. Probobly cost you about $5 each one, so It's well worth it. There are five orings in total. the big one around the cover, the two on the posts/locks and two under the posts where the tube go down (just unscrew the posts).
As for the Pepsi.....Two of the three soda kegs I have had Coke in them and that came out without any problems....1)I left them pressurized until I cleaned them so the Coke wouldn't dry out and 2) Lots of hot water to get rid of everything....Plus some oxy-clean....BUT NOT BLEACH....Stainless doesn't like that stuff.
Secondary #1: MT Secondary #2: MT
Conditioning: Nothing Drinking: Store bought
On Deck: Festa Brew Red Ale....As soon as I get my bucket back from storage.
All bottles are Guinness bottles, Plus Five Kegs!!!