One mechanic made it sound like it was a difficult job so I wanted to have some kind of idea what he meant.
I had a suspicion that it was the AOS but I also knew of a pre-existing coolant leak (it was leaking on the ground), but the car never overheated or even went unusually hot. There were a few problems that all happened at once. Bad luck for me
Thanks very much for the explanation.
take care,
kevin