When I apply the brakes I get a ''knocking'' noise from the front

Hi Erica:
Time to play automotive detective...........
Does it happen when"
- the vehicle is stopped and the engine is running?
- the vehicle is moving with the engine running?
- the vehicle is moving and the brakes are applied?
- the vehicle is accelerating under load (uphill)?
Is the noise constant
intermittent
only happens going over bumps

Reply as a comment to this post and we'll try to help.
Cheers.

This could be the break pad retaining springs. If the caliper assembly leaves a gap for the break pads they will make noise. Remove the wheel and look to see if the brake pads have excess room.

Problems with cv joints can cause this noise when turning, stopping. Eventually the joint just gives way and you go no where!

recheck brakes hard ware may also been bad , ck front wheel bearing also.

Volvo brakes scare me. I have been a mechanic for about 15years and I no longer use the bolts that hold the calipers on when the car leaves the shop. Bolts do an odd thing referred as 'stretching' in where the barrel of the bolt becomes an hour glass shape. When this happens to a bolt it loses a lot of its friction and can come loose. If you have had the brakes done recently then this is most likely what has happened. If you are able to jack the vehicle up and support it, then remove the wheel, on the wheel stub, you will notice the caliper. Behind it are the mounting bolts. one set mounts the caliper the other or a spacer. Check the torque on both before driving any place as this can become extremely dangerous, and costly.

its sounds like the shims where not installed on the brake pads like they should of. or the pads are glazed from overheating

Right front motor mount is bad ??

big bang theory.

Ok, I've never heard of this happening to someone. If you turn left or right and apply brakes there is no noise. That means that the front end is probably ok. If it doesn't seem loose that way.

If you have a Sears nearby take it to them so they can listen to this banging.

They probably won't charge to look at it.

It's the right front wheel bearing. When you turn the steering wheel it unloads the bearing and that's why the noise goes away. You won't replace that yourself, find a shop to confirm it and give you a firm estimate.

sounds like a bad speed sensor in a wheel, or possibly a tire mismatch (different size tires on car front to back or one odd one) Abs can be turned off and will work in normal non-abs mode by pulling the appropriate fuse...This may help 'till you get it figured out.