huge *clunk* during braking...HELP.

[SixLug]

Ok, this *just* started today. I have no idea why. As I press the brake pedal slightly, it slows down fine. If i press it down kinda hard, it clunks like crazy up front and underneath me it seems, and the right rear wheel locks up. It also stops really quickly...it feels like as I press the brake pedal, it does nothing, then all of a sudden the brakes grab really hard and fast. There arent any leaks, there dont seem to be any problems underneath, but ******? The only thing different is that I dont have my front bumper on...I see no correlation between that and the brakes, but it started the day after I took it off. HELP.

Oh, and it doesnt happen at all in Reverse...it works perfectly fine in Reverse, it only happens in Drive.

 

[goodtimes]

Drum brakes (on the back)? Disk?

Either way, step #1 would be to pull the tire/wheel off, and have a look....is everything where it should be, and in the correct shape (not bent/broken)?

 

[sandalscout]

IF the rear is locking up, pull that wheel and drum, the rear drums are a PAIN to adjust, I got mine all back together, and on of the springs popped off and did something similar, was fine in reverse, all kinds of messed up in forward, do to the primary shoe changing when changing direction.

Good luck!

 

[Martyn]

I had a similar noise when one of my calipers was loose. The noise was heard only when going forward not in reverse. Tightening the bolts that secure the caliper remedied the problem.

That said I did not have any of the other issues you have reported.

 

[SixLug]

Its a cherokee with drums out back. I think the wheel cylinder is sticking and popping the pad out into the drum really hard. I did take it all apart and looked and it looked fine, but one time, I left the drum off, turned on the jeep, hit the brakes, and the wheel cylinder was leaking out of the side towards the front, and it also didnt retract, which makes me think its binding...sound correct? I was just going to change both side pads and wheel cylinders and hope that fixed it...

 

[JeepN95YJ]

If you hit the brakes without the drums on, you overextended the wheel cylinders. This has nothing to do with the shoes retracting. Essentially, the drum needs to be in place to make everything work. You probably didn't do any damage as long as you put everything back together properly.

I'm not saying your wheel cylinders don't need replaced, only that the fact they didn't retract doesn't make them bad. They are not designed to work without the drum.

 

[SixLug]

ok...but shouldnt the return springs return the shoes to where they should be, regardless of if the drum is there or not? Just askin...

Anyway...its a strange strange world. So after fooling around with it a bit, I adjusted the shoes out until the barely touched the inside of the drums...they were way in previously. I dont know if that did it or what, I put it all back together to head to autozone for a new wheel cylinder and it clunked much quieter a couple of times and then....nothing. Like it never even happened in the first place. Stopping hard, stopping slowly, reverse, forward...works fine. No leaks...******? Whatever...I guess I have a spare pass. side wheel cylinder...

 

[Grim Reaper]

Who did the last brake job? Did they mix up the adjusters and get them on the wrong side? Were they frozen requiring a lot of effort to get them to adjust?

 

[SixLug]

no they werent frozen...easily adjusted by hand. And Im not sure who did it...Ive only had the XJ for a couple weeks.

 

[JeepN95YJ]

ok...but shouldnt the return springs return the shoes to where they should be, regardless of if the drum is there or not? Just askin...

No, because when the wheel cylinder over-extends it causes the shaft to fall out of the cylinder. When it does this, the springs cause the shaft to lean over or bind without the support of the cylinder. They also leak when this happens because it binds the seal.

It sounds like whoever did the repair afterwards ran the adjuster all the way in to re-seat the shoes.

 

[sandalscout]

The adjusters on XJs are renown for not correctly adjusting, it might have simply been that that they were too far in (did the e-brake engage when only pulled WAY WAY up?) and the loosened assembly was popping around in a manner it shouldn't.

I have to readjust mine rear brakes because the e-brake is only grabbing when pulled all the way up, and it interferes with my cup holders. I've read that some guys have to adjust them on a monthly basis.

 

[SixLug]

wow...I guess Ill keep my eye on that then. Yeah, actually, I dont even think that the ebrake was engaging. But I adjusted them until they were almost touching the pad and it seems to have fixed it. Only time will tell...

 

[madizell]

No, because when the wheel cylinder over-extends it causes the shaft to fall out of the cylinder. When it does this, the springs cause the shaft to lean over or bind without the support of the cylinder. They also leak when this happens because it binds the seal.

It sounds like whoever did the repair afterwards ran the adjuster all the way in to re-seat the shoes.

Even if not overextended and unseated, the return springs on each shoe pull on both shoes together. There is no "return to center" feature on brake cylinders, so with the drum off, the springs will return the cylinder pucks to a hydraulic neutral position, but that position will probably not be "centered" in the area of the drum. In fact, you can float the assembly back and forth in the fully retracted position, and probably will have to do so, to get the drum back on. Drum brakes are intended to move only a small fraction of an inch from retracted to extended against the drum. The drum essentially centers the brake assembly over the wheel cylinder.

You can gently check brakes for function with the drum off, but don't floor the pedal. The master cylinder has far more stroke than the wheel cylinders, and you will unseat one or both pistons in the wheel cylinder, causing leaks and such. As mentioned, this doesn't break anything, but it does make a mess, and you should take the cylinders completely apart and verify all parts are properly in place, rather than trusting to just shoving the push rods back in place. It pays to take them apart anyway, just to verify the cylinder condition. It should not be pitted, but there is a chance they will be because brake fluid picks up moisture, which migrates to low points in the system where it causes rust. Pretty common. It is also common to have rust and debris in the cylinder bore toward the outside of the cylinder under the rubber cap. Overextending the cylinder drives the rubber piston cup over that debris and rust, which can abrade or tear the cup. This will either cause immediate leaking, or will result in a leak soon. So if you have overstroked the cylinder, take it apart and check everything out before returning the vehicle to service.