Volvo: Timing belt, timing belt tensioner, hole haven

Question
Timing belt tensioner on my girlfriend's '90 S70 came apart at about 75 mph, threw belt. Top of one piston damp with oil, seen through plug hole. Haven't pulled head yet. What's the chance this is from bent valve, rather than broken piston? Also she had last belt done by dealer at 70K and was coming up on another one at 140K (car has 132K). Volvo replaced the belt but not the tensioner, although I saw on the web, they recommend replacing it with every belt change at 70K. Does Volvo have any liability, after this amount of time for not following there own recommendation?

Answer
Doug,
Most likely it has bent valves and only slight dimples in the pistons.
The dimples are nothing to worry about, if they are only dimples. You
can tell more with the head off.
A good shop will advise the owner of the potential problems of only doing a belt and not a tensioner or pulley or water pump. Those additional parts raise the cost of that repair, and some people think that the shop is just "selling parts".
As far as liability I doubt it, however the dealer maybe willing to help with some costs if they do the work. I would talk to the service manage to see if you could in these tough times strike a deal.
If you look into the service maintenance book it is not listed as a necessary replacement.