TripleBee
I bought a new one.This is exactly what has happened to mine - the glue for the locking sleeve appears to be totally inadequate thus the locking sleeve comes away with the water filler cap - took me a few minutes to work out. What adhesive have people used to re-attach the locking sleeve to the body ?
My problem was that the plastic pins which are tightened with the metal nuts, were broken off.
When replacing, I noticed the glue had started to get loose too! So I still have my original cap.
The thing is just not too well thought. It had to be in one piece, and the connection between the unit and the water tank is just too firm. When the watertank moves, while drivng, there is too much stress on the filler neck.
It had to be a more flexible connection. But on the other hand, I am no engineer, so I am underpaid, and I know nothing about California's (for the almost 10 years I have it).