Need some advice,

My central locking pump seems to be overrunning so my initial reaction was I have a leak somewhere around in the system. Anyway been searching for the leak, but can't find one (easily), so with a mate we disconnected the vacuum lines from my pump and blocked both vacuum holes to see how long it ran. It runs for about 30 seconds, which my mate reckons the pump is faulty. Is there an easy fix I can apply to rectify this before it shatters again (It only got the internals replaced a couple of months ago from a vw breaker).

Do you guys think its the pump from what I am describing, and can it be repaired easily in this state or am I going to be 'had' again - cost me £100 first time round