What does it take to get these things to seal? The new Autospecialty (TRW) brand unit I recently installed a month or two ago is starting to seep from the cover, and I noticed there is a minor bit of surface rust on the sealing lip. The old one it replaced also did the same, but htis one seems more significant of a leak.

Is there any magic to getting these units to last, or am I just having bad luck with them, the internals going bad and causing excess pressure in the resevoir? I wonder if the parts store will warranty it and let me get one of the aluminum ones instead....

You can buy a new rubber seal (that goes under the cap) in the Help section of an auto parts store and see if that helps. Definitly clean off the rust on the sealing surface though.

I think I have given up on iron units. I have a feeling even though if I could get the cover to seal on my current unit, it still needs replacing.

I'm trying to locate a 1 1/32" (84-89 diplomat) aluminum unit and buy the AREngineering adapter. It appears all the modern new replacments are iron as well, so I may have to buy a rebuilt unit to get an aluminum piece.