Car Doctor: Old discs and oil leaks

Q. I have just bought a used car which is almost ten years old. I noticed an odd humming sound when I brake. However, the car still feels fine and this only seems to happen when the car is in gear.
J. Simpson, Swansea

Q. I have just bought a used car which is almost ten years old. I noticed an odd humming sound when I brake. However, the car still feels fine and this only seems to happen when the car is in gear.
J. Simpson, Swansea

A. We think that the discs and pads could be very old and are what some specialists describe as being "glazed" as two polished surfaces rub together. They believe it is best to replace both the discs and pads to be on the safe side.

Q. I've got an oil leak under my bonnet and I can see exactly where it is coming from, the oil filler cap. I like keeping my engine bay clean and this really bothers me. I went and bought a brand new one but the problem still persists.
M Fredericks, Derby

A. The camshaft cover into which the cap fits may be damaged. It could be cracked which means you will need a new one. Otherwise simply bending the tabs on the filler cap towards the rubber will help. The cap may become harder to remove but that is a small price to pay. Otherwise in order to make a tighter seal a small amount of crease can help keep oil at bay.