I had something similar happen last year.  Since the tank was pretty rusty, I ended up buying a new tank (with internal fill valve) from Bus Depot.  I think the fill valves can be rebuilt, but the thought of what could have happened when the tank vented was enough to make me want to be sure it was done right.

Bill

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Volks,

I just got back from the Moab feed store to fill the propane on my 89
Westy. The auto stop has a pin hole size leak at the center of the
bottom of the valve housing which allowed the entire contents to
escape into the atmosphere. I'm back where I was with an empty tank.

The sheriff was there and lay down in the dirt and banged on it with a
crescent wrench. Didn't help. He suggested we call Moab RV and get
technical advice. I explained the symptoms to that person and he said
(quote), "Is it on a Volkswagen?" I admitted it was and he suggested
the internal diaphram was ruptured and the hole was a design feature
to allow gas to escape in that event. He said he didn't stock new ones
and neither did anyone else. He suggested I check bone yards. Now,
Moab is the home of the world famous Tom Tom's VW Museum (and used
parts emporium), but he don't sell used parts.

Any suggestions. YES, I did an archive search and the usual commands
yielded no results.

Any helpful advice appreciated.
Fred