Just soaking them in PBW or OXY isn't enough. If this is the first time you are cleaning them then dismantle the kegs entirely, clean thoroughly and replace all the O-rings & lube them. Get a dip tube brush or make something to scrub the inside if the tubes, especially the Liquid/Out tube. Use a brush to scrub the inside of the keg. Then rinse & sanitize with starsan. At each step make sure you run the liquid (PBW, water,starsan) through each post & the relief valve. Cheers!!!