Tighten the "bolt" just enough to make the seal. Resist the temptation to "make sure it doesn't come loose again". If you overtighten that bolt, the cooler can be crushed and leak internally.
There is a simple square cross section seal in there that doesn't require a lot of force to seal properly. You may want to clean the mating surfaces in there before tightening it up. New seals are available from the dealer if you need one.
Good Luck!
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rcgreer@tap.net 92 Laser RS AWD