Brakes Acting Oddly

[PeteA216]

Hey guys,
For the 5 years of owning my '84 Caprice the brakes have always been decent. They were never very firm, but never squishy either. The previous owner had replaced the front calipers, rotors and pads. Since I've owned the car, I've replaced all brake lines excluding those form the master cylinder to proportioning valve. I've replaced the rear brake cylinders, and put in a new set of springs, clips and pins. The front pads have been replaced, and fluid has been bled thoroughly on a yearly basis. Nothing had been touched on the brakes for about a year now except the end of the brake line that leads to the T- fitting for the rear brakes (about 4 weeks ago). Just yesterday while braking I heard and felt a "clunk" and suddenly the brakes felt very tight. to stop the car, very little pedal pressure was needed. This morning the same thing happened while backing out of my driveway with the "clunk" and the whole way to work the brakes were very touchy. Then again, the same thing happened goign out to lunch. What's going on with my brakes. I like how touchy they are now, but I can tell this isn't right.

[silicon212]

Check either master brake cylinder or brake booster. One of these is likely on its trip south. Also, check to see if your emergency (parking) brake pedal is lightly pressed. The light won't ALWAYS come on when it's lightly pressed.

My 2¢.

[GreyGoose006]

mine is like this at first, but goes away after a few stops
i think it is pressure related though in my case

[PeteA216]

Check either master brake cylinder or brake booster. One of these is likely on its trip south.

When searching for vacuum leaks about a week or so ago I checked the brake booster and it was fine. How do I check the master cylinder? If something was going wouldn't it work worse instead of better? I also noticed something... my exhaust header runs directly next to the proportioning valve about an inch away. Could the heat of the header have caused any damage? I see in other cars headers running very close to brake lines, power steering gear boxes, and other things and they all seem to be fine.

[bobss396]

Brake lines too close to headers will actually leak and lose fluid, so that's not your immediate problem. Wrap the lines with heat shield material or bend/route them out of the way if possible.

What do I always say? Do the cheap and easy things first. I'd change the brake booster check valve and see how it goes from there.

Another thing, have you had a bunch of rain lately? Sometimes the shoes/pads will soak up moisture and be grabby until they dry out. That can make the noise that you describe.

Bob

[PeteA216]

We've been without rain for a few weeks now. The check valve was replaced last fall when I accidently cracked it while taking it out for inspection. I'll use the same heat sheilding on the brake lines that I did on my plug wires.