What happens if the serpintine belt breaks?
 

Hi

I have a 99 S80 2.9 now with 181K miles on it. I last got the serpintine belt replaced at 81k miles back in late 2005. Since then I put 100k miles on the car (all highway miles). At how many miles should the serpinetine belt be replaced 60k or 100k miles. And what happens if the serpinetine belt breaks, will it cause some kind of engine damage.

Replace the serp. belt if it is cracked.
Sometimes if it brakes it will get sucked into the timing belt and break that one as well and damage the motor.

How can it get sucked into the timing belt, isn't it (timing belt) inside the engine cover or whatever it's called?

There is a gap where the timing cover is by the crank pulley. There is room for it to get sucked in.

I have seen that happen to many times!

I can back up what Tech's saying (not that he needs it ;) )

I ordered a LKQ motor to replace the blown one in my s80... after the first coming in with a seized crank, I got a 2nd one, and it had the serp belt stuck in the timing belt near the crank, causing it to skip teeth and bend valves in the head... it can and does happen!
Thankfully the third motor was good :)