Just wanted to throw this out and see if anyone had input.

Early this spring I was driving a dusty back road to the next town over (about 7 miles) and the front brakes started to smell like they were burning. We pulled over and whacked them with a rock to unstick them on the driver side, which worked just fine, but then the passenger side stuck and began to smell and smoke a little. Whacked that one with a rock, just trying to limp home, and made it to within 4 miles of our house before we had to just pull over and walk and leave the Jeep to cool down because it was billowing smoke from the passenger side front brake. When we returned after dark, the brakes were unstuck and we had no issue getting it back home and into the garage. We got busy so it's been sitting for a couple months now, but I'm ready to be driving my car again... I'd just drive it around the neighborhood and see what happens but I'm concerned about them getting stuck again, starting a fire, or going out entirely (we live in the mountains, so a sudden brake failure means I'm going straight into the river or through someone's living room window.)

Front brakes were replaced almost exactly 2 years ago after a stuck caliper issue and the Jeep has mostly been driven long distance between Albuquerque and Southwestern Colorado. Not much daily commuting. No other brake issues until the almost-catching-on-fire-on-the-country-road incident, except that they were a little soft in general. When jacked up with the tire off, there is no visible corrosion.

I'm ready to get up in there and get whatever it is fixed, but I haven't the slightest idea where to start. Just replace the brakes altogether? Could the issue have been caused by an air bubble in the brake line? Bleed the brakes and see what happens? Could the issue be caused by the fact that it sits a lot and is used more for long distance travel versus a daily driver? Are there insidey parts or pins somewhere that aren't a standard part of a brake change that could be corroded?

Any ideas or suggestions would be great. Vehicle is a 1991 Cherokee Laredo 4.0. It is definitely old and rusty in places, but like I said, the brakes were replaced fairly recently and don't have a lot of miles on them compared to a daily driver. We do live in an area where the only paved road is the highway, so there is a lot of dust. Jeep was purchased about 5 years ago from a family who drove it on the beach for years, so salt and dust could both be involved.

 

Is there a groove worn into the knuckle where the pads make contact? That's a common cause of pads not releasing properly. Also, be sure the guide pins are properly lubed.

 

Try replacing the brake hoses. Sometimes they collapse internally.

 

On prior brake work did you just replace the pads or have the calipers been replaced or reconditioned. The guide pins should be cleaned and lubricated with special brake grease on every pad change or they can seize up and do as you describe.

 

all good suggestions above, can also be a faulty master cyl

I would 1st check the steering knuckes for any groove where the caliper slides..it must be smooth...a worn groove can be welded and ground smooth

next replace the front hoses..cheap, and they are old

if that fails you are up to rebuilding or replacing the calipers or master cyl

 

+1 for checking your knuckles for grooves. I've heard that as a half-baked stopgap, you can carefully blend them out with a fine file.

On the lighter side, I'm assuming you travel US550...one of my favorite drives. You are in the enviable position of being able to stop for a bite to eat at El Bruno's while you let your brakes cool. The closing of the Cuban Cafe was a regrettable occurrence.

 

On top of the other suggestions, if you choose not to replace a caliper or brake hose, bleed both front brakes before you drive it. When they overheated, fluid may have boiled leaving air pockets in the system. While bleeding, check the colour of the brake fluid. If it looks black to start with, that's a good sign that something rubber is deteriorating in there.

I personally had the worn grooves in the knuckles and it was an easy weld and file down repair.

You can also remove the caliper and carefully pull the seal away from the piston and check for any signs of rust in there. If it is rusty, it's best to replace the whole caliper as it won't get any better.

 

Has anyone tried using WJ knuckles? They have bolt on caliper brackets and dual piston calipers. It might be a problem using XJ rotors though. If not, you'd have to switch to 5x5 WJ hubs. Too much work.

 

I haven't done it, but looked into it. Can be done with a little bit of fab work, or at one time Rusty's had a conversion kit. You can run XJ hubs but they have to be spaced out from the knuckle. Have to run WJ knuckles, calipers, and rotors. It also converts the steering to a crossover style arrangement.

 

Yeah, But! How do you run WJ rotors on XJ hubs? The bolt pattern is different.

 

Ahhhh, yes you are correct. I looked through my research notes and links and can't come up with an answer. Everything basically says "reuse your XJ hubs" and "new WJ rotors". Kind of glosses over the fact XJs are 5x4.5 while WJs are 5x5.... There were a number of reasons I ended up not liking the conversion, and this is just another one.

 

Yes! We live in Ouray and I was in Albuquerque for law school through most of this Jeep rebuild business... I used to stop at the Cuban Cafe all the time. So you know why I can't just drive up Red Mountain Pass with questionable brakes...

 

Thanks for the tips everyone! It is 100% grooves in the knuckles. They're nasty deep. We've just been all up underneath the front end this afternoon.

So my next question is this. We were looking into getting a welder anyway, but now that we're shopping around, have decided we can't make that purchase right now. Filing them down also doesn't seem like an option. They're just too deep and it would be doing more damage than good to the knuckle itself. Instead, we're looking at replacing the knuckles. While we're down there with everything taken apart, does anyone have strong feelings about whether there are other front end repairs we can make? Everything seems to be in pretty good condition considering the dirt / mud / salt / age of the vehicle, but I feel like while we're replacing the knuckles, it would make sense to do some preventive maintenance on the rest of the front end so we don't have to take it all apart again in a few weeks. The Jeep is generally at that age where "everything is great, except..." then we fix the except and another one springs up immediately out of the blue. You know the dance...

The only other possibility we're aware of is that when I got new snow tires put on in December, the guy at the tire place said that one of the front wheel bearings was going. I have had zero symptoms of an unhappy bearing, and checking it out just now we weren't able to even determine which side this supposed bad bearing is on. Everything seems fine. But for the sake of just in case, would it make sense to replace the bearings and the brake knuckles at the same time? Or not bother because they seem to be just fine... or anything else we should just scrap and replace while we're down there...

Finally, are there any brake changes or modifications we could easily make right now while a major part needs to be replaced? Like is there a different type of system that anyone recommends that this would be a good opportunity for us to switch to? Or just fix what we have and wait for the next thing to break.

Again, thanks for the diagnostic help! Now I just need to make some choices about how to best address it.

 

I'd check your ball joints for any play and also check your universal joints on the front axle. You have to remove the front axle shafts to do the knuckles anyway so all of the work to get at the UJ's is done. Same story with the ball joints, everything you'll remove to do the knuckles, you'd have to remove to do the ball joints.

Depending on if you have the time and parts availability, while sorting the knuckles you'd remove the bearing hubs. When removed it'd be rather easy to tell the condition of the bearings, providing that you checked for up/down left/right play prior to removing the wheel and found nothing. If the bearing seems to have no play then once removed, give it a spin by hand. It should have slight resistance if it is still greased and should feel smooth with no noise. A greased bearing that spins freely is a greased bearing with no grease left.

Another tip, if you feel up/down play at the wheel, get someone to press the brakes and try again. If the play goes, it should be bearing, if it remains, ball joints. The brakes end up locking the hub and wheel together bypassing bearing play.

 

The reality is every part of a 25yr old XJ suspension will be worn, and could justify replacement, thing is you cant go cheap on some parts

If you replace the knuckles, be aware used ones are often grooved..you would have to do the ball joints, it would make sense to do the unit bearings & uni joints as a minimum

honestly, it is easy to clean up the groove, pre-heat, weld, grind & file smooth & nice...I personally feel this would almost justify the purchase of a MIG...does yr XJ have any rust in it lol?

ie you can have it fixed and back on the road today for less cost than any other method...and you will own what I consider a necessary tool for auto repair work