2006 Chrysler Sebring keeps having problem with Thermostat housing what to do?

My 2006 Chrysler Sebring is on its
2nd thermostat housing repair. The
first time the part had decayed away
(I bought the car used so this was
my first time with this problem and
this car) when it was replaced the car
ran great every now and then when
the air or heat was on the car would
shake and sometimes shut off but
giving a little gas would make that go
away. Now I was sitting in my car for
a few minutes and the top of the
housing using literally popped off of
the bottom half of the part. There
was smoke and coolant everywhere.
I know this piece is plastic but what
would keep causing this to happen?
I don't want to be stranded one day
or worse. Please help.