Brake rattle

Thanks for all your help answering my various queries but I'm afraid I have one more.
I searched this site for any problems with "rattling" but had no joy.
My GTD has a pretty standard early brake setup, twin servo's, standard master cyl, drum rear, with the exception of AP calipers (stsndard discs) at the front.
The brake servo doesn't seem to be working too well, but after my previous post, I thnk I have it explained and will be addressing the problem shortly.
My problem is that the front left hand pads seems to rattle in the calipers. As soon as I touch the brake pedal it goes, but as soon as I take my foot off, it rattles again.
I remember reading somewhere about a "residual pressure valve" and was wondering if this is what's needed to fix the problem?
Are the pads supposed to have anti-squeal plates behind them?
I can post pictures of the calipers if needed.
Thank you

John
Typically the residual pressure valve would be in the line either to the front or rear beakes as a pair, since you are experiencing a problem with one caliper it seems that you may have a mechanical problem. Obvious problems may be that you have a leak whick would be noticeable right away and I doubt that is the problem. I would check that rotor for runout, a loose bearing on that wheel, or even the caliper to make sure it is also tight. I have seen this problem before, and it can be a bugger. I would also check the integrity of that set of pads to make sure no pieces are missing, or the metal backing plate is worn enough to cause a loose fit. Most over-the-counter brake pads sold here have some type of pressure sensitive backing pad installed at installation to stop that chatter, and a lot of mechanics put a dab or red RTV on the contact area between the back of the pad and the piston as a fix for some of these problems. I would bet something is loose there. You didn't mention if the car pulled to the right on application until the pads make contact, this would be an indication of the things I mentioned.
Hope this helps a little
Cheers
Phil

John,
sounds to me like the spring things haven't been fitted, allowing the pads to rattle on their pins.

The backing on the pad Phil refers to is normally to stop squealing (pads rubbing on the caliper pistons). Competition pads don't have these, but road pads should. ON some cars it isn't so much a pad as a thin metal disc that clips inside the piston.

The only other things I can think of is the disk is somehow floating, the caliper is loose, or the disk has a lip on it so it is contacting the pad metal backing.

Hope you manage to find out what it is. I hate rattles and know howe annoying they can be !

Cheers,
John.