I highly doubt its common for any radiator failure at 31k, but to be more specific, I havent heard of any radiator issues at all, sounds like you took a pebble through the grill maybe.

You can do a little experiment is its leaking that much without any pressure.
1) Start by draining the entire radiator.
2) Then fill it as quickly as you can measuring how much you are putting in. When its full you will have the basic capacity of your radiator.
3) Now let it leak til it stops leaking, then refill it to the top again....again measuring how much you are adding.
4) This will tell you about how high or low the leak is coming from.

Pretty low tech, but its something to try.