Hi, welcome to Just answer! My name is Ross and i will help with your question
could you please tell me the prob
I will do my best to help you cure the problem, first, can you explain when the knock happens? Is this a one off clonk as you hit the brakes ?
when the brake is applied
Ok, does it knock once or is it constantly knocking until you let off the brakes?
just once like something is moving
Ok, would you say its from the front or rear ?
front if u put brake on knock of no nock on knock
Right, its usually the brake pads knocking, as you press on the brakes, the pads will move in the carrier which goes with a knock through the car. Were the brake pad lugs greased?
yes it had a new caliper on as well and a second set of pads
Ok the pads can knock like i said before, this is the most common cause if the pads are not tight in the carrier (if you can rattle them up and down ) they will knock, the other cause which I see quite a lot is the sliding pins between the carrier and the calliper, these seem to wear out in the carrier, the pins are usually ok but the hole it sits in becomes oversized allowing the calliper to move up and down, it will return to its normal position when you let off the brakes and then knock as the pads pull it downwards on braking .
seems strange it still does it with a new caliper and fittings just the same as the old one there is slight play in the wishbone
Yes movement in the wishbone will knock, its usually more of a thud but if there is any movement in the front or rear bushes of the wishbone this should be cured first as it will only take a small amount of movement to make quite a substantial noise through the car.
do you need any special tools to replace the bushes
Most auto factors will stock the complete wishbone with the new bushes pressed in, they are not much more expensive than the bushes but otherwise ideally you do need a workshop press to push them in and out, however you can knock them in with a copper mallet, its a bit fiddly but they go in quite easily.
would this play make the car move around when braking
Yes, it can do, any movement in the lower arms will, if there is movement in these bushes this will be my first suspect and not only that its going to be an MOT failure if its excessive which it sounds like it is so i would advise you replace the wishbone before anything else is done. I think that will cure the problem.