How can you repair the vacuum pump for the brake booster on a 1992 Vauxhall Frontera?

I'm not familiar with your vehicle, but MOST vehicles do not use a vacuum pump as a source for booster operation. Most use engine vacuum, which is obtained with a tap from somewhere on the air intake manifold system. If you follow the vacuum line [rubber hose and/or metal tubing] back from the booster, you will find the source. Usually, brake booster vacuum failure is the result of one of the connections of the vacuum line[s] being disconnected, cut, or dried out and cracked. If a vacuum system leak is the cause of your problem, repair is simply a matter of identifying the point[s] of leakage, and correcting. If there actually is a vacuum pump, then I have misled you, apologize, and cannot help. If this is a diesel,then you will have a vacuum pump.Usually drives off the end of the cam,couple of pipes and bolts and it's off generally. I don't know what is available from vauxhall,there may be a repair kit,you need to phone local dealer to confirm.Usually only a 3-vane rotary thing,remove the end plate and all is revealed.If no spares available then it's a choice of new unit or the scrapyard for a 2nd hand one. Answer 3 As far as I know you cannot buy a repair kit you will need a new one.