Lid leaks on corny, was holding pressure for months?

I got a used keg in the mail from some guy on ebay. It was holding pressure fine for weeks, so I cleaned it out and filled it with iodine solution.

But no matter how I try I cannot get the lid to seal again. The gasket looks fine. I flipped it around and tried moving it around and holding it up tight while clamping down, but the seal is so bad that just tipping the keg releases pretty good amounts of liquid. How the heck did this hold pressure?

If i Put 2 stacked o-rings there it holds sometimes, but I am just wondering if there is some trick I mighta missed. I am new to kegging. thanks

Maybe it was lubed with Keg lube to make a good seal. Try that or some unscented Vaseline if that is handy. Try putting some shims under the little plastic feet to give it more tension.

Just to clarify, does it hold pressure once you hit it with CO2? Are you saying the lid lets liquid out even once it is pressurized?

Look at the lip where the o-ring seals. If it has a visible dent you might need to take a persuader to it and even it out.

Thanks, I will try vasoline and and shimming the feet. These ideas give me enough confidence to go ahead and try filling it with a batch. The top had some damage to it which is probably giving me the trouble.

I just spent about 10 minutes addressing this same issue with a pair of channel locks.

Carefully rebend the top, and if all else fails, when you pressurize, crank the gas up to 20-30 psi and click the valve on, and it should seal. Then just turn the reg down and vent it a little at a time.

I got 4 kegs mail order that held pressure till I opened them --- then only 1 of the 4 worked right.

New pressure relief valves and big Orings solved it all.

Worked better than "lube" for me.

I made a writeup a few years ago that might help you.
Getting Your Keg Lid To Seal

williams brewing sells some extra fat, softer than normal lid o-rings that work well on used kegs.

I just got three kegs on craigslist. couldn't get em to seal with pressure at first. If I pull up on the lid then pressurize it seems to work out just fine tho.

Don't fill it with a batch until you're sure it's holding pressure!!