If you can degrease it thoroughly you may be able to get away with Silicon Gasket Maker and / or JB Weld, etc.

Depending on the size of the crack you may have to remove the cover first and put the bead down thick, a minor crack you may be able to patch from the outside. Remember you are not holding against pressure, just need to make a barrier.

There is always duct tape too! <img src="/forums/images/graemlins/notooth.gif" alt="" />

Jeff
96 T100 SR5 4WD Ext Cab, Warn Hubs, HD torsion bars, Bilsteins, Camper Shell, TJM bar, factory 31 x 10.5's, Powertrax No-slip rear, Recaro driver's bucket