Knocking when braking.

[scudge]

Hi,

(audi a4 2.5 tdi sport - estate) 2002.

I have just returned from 3 weeks away. The car has not been used in that time. I drove the car today and noticed when i brake there is a knocking at the front and intermittent pressure can be felt pressing under the brake pedal. The braking feels slugish and feel if i was to brake hard somthing might give.
The pads are all new, brake discs are low but look ok apart form the rust around them.

An help would be appreciated.

Thanks!

[spartacus 68]

This weather isn't great for a car sitting about. You'll really need to give it an inspection. Could be a sticky piston (corrosion) which is causing uneven wear on the brake discs (heat spots). Easiest way to tell is to drive the car for 10 miles or so and avoid braking where possible. Coast to a stop and feel the discs. Should be cool to touch. If they're hot you'll probably smell it before you touch it. If one side is hot - then more than likely it's a sticky piston or siezed slide-bolts. Only fix is dismantle and rebuild. Use lithium based grease on slide bolts and Lockheed red grease on the caliper bore before inserting the brake piston. Replace the rubber dust sleeves and fit a new piston 'o' ring. Ensure there is a liberal smear of Copper Ease on the back of the pads before installing. Bleed brakes in sequence (furthest away from brake fluid reservoir first) and use DOT 4 spec fluid. Don't over-torque brake bleed nipples.