Noisy vacuum pump
 

The brake vacuum pump on my wife's 99.6k miles 2008 C30 T5 has started to make an extremely loud and high pitched whine on some occasions when the car is started. The whine then continues for several minutes before fading out. Searching the web reveals that this is commonplace.

The car was however serviced the day before the noise first started. I am minded to think that this is merely a coincidence and the pump probably has dry or worn bearings but could anything performed in a minor service cause the pump to overwork and eventually become noisy? I can't think of anything that would disturb vacuum lines for example.