I was finally able to fix a problem on my 2001 Durango, when I would put my foot on the brake there would be a slight delay and then a click as soon as the brakes engaged. And sometimes it felt like there was a total loss of brake booster (having to push really hard to stop) with a slight hissing noise under the dash. So tried bleeding brakes, changing calipers, wheel cylinders, etc. the cheap stuff right. Anyways, ended up being the brake booster (and probably the master cylinder). Brakes work like a dream now, what was happening was the brake booster was leaking by internally and losing vacuum. I didn't suspect the booster right away because it never got worse. I replaced the master as well because I read online that boosters fail when the master cylinder leaks into them. Really easy to change out actually.