When gently braking at slow speeds, loud bang from (I think) front driver wheel. And when I say loud, I mean LOUD. It shakes the whole vehicle. Almost sounds like I'm hitting something but I don't think I am. The bang happens once per braking, and only happens when braking, not accelerating or releasing the brake. Not a clunk clunk clunk sound or anything like that. I just roll forward gently, apply the brake, and after a moment of easy braking, BANG!

My suspicion is that my caliper is sticking and then suddenly releasing, but I haven't found anything like this problem on any forums so far.

Ideas of how to fix or diagnose?

1999 XJ Sport.

 

Need to start with the obvious and pull the front wheels and look at the calipers. But I would look at every joint and connection point in the front end. Also, when you first jack it up, take a bar and put it under the tire and lift. See if you feel any looseness in the ball joints.

 

you may have lost a caliper bolt. check that and also with your foot on the brake, shift from forward to reverse and have someone inspect your control arm bushings.

 

I could see something like that happening too. Those would make a racket if there's play in them, especially with the weight of vehicle and a solid axle. Could be one main thing like that or a combination. So check other things too. ball joints, Also make sure your springs are seated properly and not damaged... along with checking to make sure your shock tower bolts are all tight. When coming to a stop that would make good noise too if you've got a loose upper shock tower bolt or two.