If you've got room without overfilling, add a pint of "Trans-Medic", or some other brand of seal conditioner. That stuff softens the rubber in the seals, and makes them seal better. Just don't overdo it, more is definitely not better in this case. If one bottle doesn't help, adding another one will make things worse!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!