AMP76

Hey all. I had noticed some clicking coming front my front end for the past month or so now. Today I left to get some coffee, accelerated up to 55 on the highway, and I was braking to a stop down the exit ramp when I felt this thump/wobble whenever I applied the brakes. I managed to stop at the bottom of the ramp, then accelerated smoothly but slowly (not faster than 30) to the store, and didn't feel the thump when braking this time, although I noticed the brake light in the dash had come on. Before leaving the store I checked the e-brake and looked behind the tire for anything obvious. I noticed a lot of greasy crud under the U-joint, but the U-joint itself was clean. I drove back home the back way, not going over 35, and I didn't feel the thump again.

I did some reading online and found this forum and read up on "death wobbles" and u-joints and clicking and then did some more looking around underneath and discovered my passenger side u-joint slides in and out about 1/4 inch each way. I think that accounts for the clicking I've been hearing, but would that affect braking in any way?

I also added a very little bit of brake fluid to top things off. After turning my Jeep on and pumping my brakes the brake light went off. I started it up and went back on the highway without experiencing the problem. I got up to 60, and got off the very next exit. As before, it started to thump/wobble when I applied the brakes, would stop when I let off, then thump again until I stopped completely. The brake light came back on as I was stopping. I drove back to my gf's place (I'm 200 miles away from my house and tools, btw) not going over 35 and didn't get the problem again.

SO... I think, judging by what I've read, I can replace the u-joint with just a trip to Napa, my lugwrench, and my sockets and wrenches that I have onboard. But, I'm not sure that the u-joint is the cause of the braking problem. Any ideas??

Caish

I would jack it up and try to move the wheel, not rotate but in and out checking for a bad wheel bearing.

caged

sounds like you have a bad/leaking caliper.

littleredXJ

You should get a gf closer to your house and tools...

Jamie57

Might be a broken Caliper bolt. Had that same thing happen to me.

Your axle shaft moving in and out has me concerned. Thats if both halfs of the axle are moving. Sounds like the spindle nut has backed off. If thats correct your whole wheel could fall off! Not fun at speed!!!

AMP76

Just to follow up...

I ended up getting a remanufactured caliper and slapping it on, band-aid style, until I get back home and can do a (long-overdue) whole new brake job on both sides.

The new caliper definitely fixed the thump/wobble (the old one was leaking), but the brake light still comes on.

I also still notice the clicking, which makes me think even more that it's associated with the u-joint, since I didn't do anything with that yet. I tried pulling on my tire to check the bearings and it was solid.

Thanks for the help!

AMP76

Did I say the new caliper "definitely" fixed the wobble? It was fine for the test drive yesterday, but today, after getting up to 55 or so, the thump/wobble came back, although this time it was more the brake pedal itself pumping up and down on its own during the thumping, rather than the tire itself doing the thumping.

As before it's OK at slow speeds, but once I apply the brakes after getting up to speed I'm f'd... Thanks in advance for any insight.....

Jamie57

Sounds like you have a seriously warped rotor. OR it's not seating properly on the axle hub.
Is the wheel and tire wobbling? Do you have anyone who can stick their head out the window and look? You don't have to be going 55 to see a wobble.
A warped rotor should NOT make your wheel wobble. A not properly seated rotor WILL. or worse yet you have a fubar'd hub and bearing assembly. Not terribly expensive but a PITA to change

Went and reread your first post. The brake light coming on has me concerned. It will come on when your fluid level has dropped to a certain point. The only way the fluid can drop is a leak (broken line, leaking wheel cylinders, calipers) or the brake parts have worn so much that the puck in the caliper, or the wheel cylinders is almost out of their bore.
Sounds like something is seriously loose or worn out.
I suggest you do a complete overhaul of your front brakes NOW or have a mechanic do it before you head on down the highway again.
I don't want to be reading about you in the newspapers!!


A P.S. here.
ALL brakes when being serviced should have new parts on BOTH sides. If you replace one caliper you should replace both. If you replace one rotor you should replace both. If you replace one set of pads you should replace both. If you reuse the rotors get them both machined so the pads have a new surface to work on. Brakes are so much cheaper than hospital bills or lawsuits

AMP76

Hmmm... hopefully it's just not seated right. It didn't appear warped when I replaced the caliper, although I didn't specifically check. I'll pull the tire off and look.

Would the rotor not seated right cause the brake pedal to pump itself in and out while I'm applying pressure to it?

Also, I'm not even sure that the wheel itself is wobbling, but what I feel is a thumpish/wobblish sensation... before I replaced the caliper, I felt it more in the front end, whereas now I feel mainly in the brake pedal (though still a bit from he front end).

Jamie57

Unless you have a straight edge it's almost impossible to eyeball a warped rotor. There are also high spots an experienced mechanic should be able to spot. those two things will cause a pedal to pulsate from the pads pushing the puck back into the bore of the caliper. Remember that the pads "Float" against the rotor all the time. not like a drum brake where the shoes don't touch the drum unless the brakes are applied.

The thumping is a concern. something is moving that shouldn't be. If it's not your brake components it could be as simple as a control arm bushing or as serious as a ball joint about to let go. Triple check everything. your life (and others) is depending on it

Caish

Did you check for bad wheel bearing when you had the wheel off or was you just throwing parts at it?

As to replacing parts in tandem, as in calipers, etc. Calipers there is no reason to replace both because one went bad. That would be like the doctor putting both arms in a cast because you broke your right one.

Brake rotors that have not been run to the metal and have a nice even surface on both sides of the rotor there is nothing wrong with replacing only one there too if needed.

XJcountry

You should always do brakes in axle sets i.e front brakes all together/ or rear brakes all together. However you do not have to replace calipers in sets, but calipers aren't that much money anyway so its never a bad idea if one does fail.

Jamie57

WRONG!!!!!!!!!!!

Tell everyone where you work as a licensed mechanic so they will know where to stay the hell away from!
There is every reason in the world to replace them in tandem.
Most of them are little sons and daughters who happen to run into the street to fetch the ball.
Calpers are CHEAP!! at most $25 bucks each. Not cheap like you!
You want the brakes to be balanced. BOTH WHEELS stopping with the same force.
And yes you can go without turning the discs but for the cost involved WHY THE HELL wouldn't you.
Don't you get it? Any goof can get a vehicle to go fast. I want to be able to STOP too.
Who are you to gamble with the lives of others just cause your to penny pinching cheap to fix your brakes THE RIGHT WAY?
Oh wait I know. Your saving those pennies cause Budwisers on sale at the 7-11.

AMP76

No, I replaced the caliper because it was leaking and the brake light was on, and because I only experienced the problem when braking. I originally thought that the braking problem was somehow in connection with my u-joint, which does have a little play on the passenger side. But since the caliper was obviously leaking (and since I'm away from home with quickly diminishing funds), replacing the caliper parking-lot style seemed like the best move to make. And the problem did go away, initially. I took it out last night with no problems at all, except that the light came back on. I also did pull on the tire to check the bearings and there was no give... is there another method?

I think I do have a metal straight edge around here somewhere I can use to check the rotor. That's exactly what it feels like under my foot, that the puck is pushing back on the pedal as the high spot comes around...

Caish

Your logic is good, but its not actually reality.
My reason still stands, one bad caliper does not make the other one bad. EVER! No reason to replace two, but when your in the auto repair business (as I use to be) I understand your markup on parts is 100% typically and then add in the extra $70 for a second hours labor.
So we all know where your coming from. your pocket BOOK so you can afford the Buds or what ever kind of crap canooks drink up there.

Again the only reason to turn rotors is if you go to long and wear it down to the metal. Then you've got an uneven and rough surface to brake against. Go ahead charge them $10 each to turn them knowing the whole time that your going to turn them thrice and then sell the customer a new set of rotors when in reality if there is no metal to metal wear or cracking in the rotor there is no reason to change it.

That being said I can also understand liability reasons from a shops side of things too. But thats a commercial shop. When the real world comes into play, and you've done literally 100's of brakes over the last 25 years as I have you know what to expect and what not to expect.

There is no reason to pull all your teeth because you have one cavity just as there is no reason to replace both calipers because one went bad. If after replacing the one and test drive it does pull one way (opposite the one you just put on) then be all means go ahead and replace the other one or at least replace the brake pads on the other side if you hadn't done it.

Brakes....
If you only replace one side brake pads (time constraints whatever since they come in pairs to both sides) your car truck whatever will still stop straight. It doesn't matter if the caliper is extended 40% or 10% there is still XXX pounds of pressure across the same area of piston. The physics doesn't change just because one side is extended more than the other.

The only thing that I ever replace in pairs is the brake pads and shoes. I've never had a brake related wreck, actually I haven't had a wreck in 20 years, much less a brake related accident and I always do my own work, so I guess that tends to back up my explanation.

So go ahead and keep telling all your customers that so you can keep buying your beer at the 7/11. You can have mine too since I don't drink, and everyone will be happy in your wonderland. Welcome to the real world where people do what they have to and don't always have hundreds of dollars to toss at a problem and pay your $90 hour to replace things that don't need replacing.

BTW welcome to the Internet where your not always the smartest guy in the room with the most experience or even the best looking. Your not in your shop with some banker that knows jack about mechanical things and has to go YOUR advice alone. There is nothing wrong with replacing parts in tandem but in reality its not needed.