That's very good of the warranty company - most of them demand failure before they're prepared to put their hands in their pockets. I've often thought mine a bit noisy, as heard with the window down and pulling up near the garden wall. But only when the car is hot and been running a while, but no other issues in terms of errant behaviour. Mine's a year younger than yours and only 67k on the clock.
Have you noticed that the pump is noisy yourself or is it just the garage noticing it?