Brakes? Stumped - JeepForum.com
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post #1 of 25 Old 06-03-2021, 02:30 PM Thread Starter
KeepOnTruckin
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Brakes? Stumped

About 6 months ago, I had somebody do brakes for me for the first time in over 30 years. My 2014 GC Limited had an occasional mis-firing cylinder code and I couldn't isolate the problem, and it wouldn't repeat while a well-recommended mechanic twice tried to figure it out. So I had him install my previously-purchased 4 Amazon Detroit Axle rotors and Extreme Power-Stop pads on front and NAPA premiums on rear. (While doing the brakes, he was able to figure out the fuel injector was bad, and everybody was happy. New brakes, and no CEL.



Six months later, driving home from BJs with new tires, I think I'm feeling a very slight shaking in the front end when braking. I assumed a tire wasn't balanced right, but when I got home, I saw a lot of brake dust on the front wheels. I promptly forgot about the tire possibility and brought the vehicle back to the brake guy.


He says the front rotors were warped. He changes them, and still no good. He then changes the rear rotors, and still no good. He then says maybe the front Extreme pads are too aggressive, and they showed some cracks in the braking material, and he changes those. Still no good. So he checks the tires, claims they're all out of balance and one of the front tires is way out of round. He re-balances them and puts the supposedly out-of-round tire on the back. He claims it's better, but it's really not. Coming off the highway, awful shaking through the steering wheel.


BJs checks the tires for me, says they all need re-balancing, likley b/c the mechanic has a dynamic balancer and BJs has a static balancer, or visa-versa, and no tires are out-of-round anywhere close to being an issue. They showed me the tires rotating on the balancer.


The mechanic says that when the new rotors still seemed to shake, he took them off and took them to a machine-shop friend, and that there was no discernible run-out. He also says that he hooked up some hydraulic hose and gauge which showed that the pistons are properly retracting, and that he can move everything with 1 finger.


When I check the temperature of the rotors with an IR thermometer, the fronts are about 20 degrees hotter than the rears.



I've found another mechanic that has just done some good work on my JK, and after test-driving the WK2, he suggests changing the rotors and calipers, and I have scheduled that for a couple of weeks out.


The first guy says he'll do anything I suggest, as he knows it's not right but can't really figure it out. Says he'll run-out the rotors again, and go from there. He can't get it in until 2 days before the new guy.


Are we missing something? Am I being out-and-out lied to by somebody? Who would YOU bring it to?



I note, again, that the first guy was well-comprehended, and wouldn't take any money the first 2 times I had it in there for the CEL, because he said he hadn't done anything; I only let him do the brakes so he'd stick with the CEL, which he found and fixed. The (new) JK guy replaced the oil pressure sensor (and the spark plugs while he was in there) for less than half what I would have expected to pay a dealer based on what I paid one a year ago to replace the oil cooler (and plugs) on the WK2.


Anyway--ideas appreciated. Thanks, as always.


KoT

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post #2 of 25 Old 06-03-2021, 03:13 PM
Bilko
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There are a lot of things going on here, if the vibes only happed after your new tires that would be the first place to look, what tires did you get?

Regarding the brakes, the front disks will be hotter, they do most of the braking. If the shaking is down to brakes you need to swap out all the Amazon sourced gear for some quality parts. If you don't want to pay Mopar prices go to your local Autozone, if they don't work you can return them.

Most of the problems I see with brakes are related to so-called "performance" brake parts you can buy on Amazon. these range from air bubbles in the rotors to pads that disintegrate or the pad material detaches from the metal backing plate when they get hot.
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post #3 of 25 Old 06-03-2021, 03:18 PM
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I forgot to ask an important question. Do the vibrations occur in normal driving or only when you apply the brakes
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post #4 of 25 Old 06-03-2021, 03:40 PM
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Thinking out loud.... A lot of brake dust may just be the power stop pads, they stop well but shed a lot of dust.

If its not the tires, rotors or calipers, then its likely a wheel bearing or CV joint. Problems with WK2 wheel bearings can mislead the best techs, and the hub moving in and out just a little will affect brake feel. You can feel worn CV joints in the steering sometimes, if you don't hear them click.

Were any of the lug nuts changed? The WK2 uses long studs and long nuts. Replacement nuts can bottom out and you have a loose wheel (or broken studs).

I just got lost in thought. It was unfamiliar territory;
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post #5 of 25 Old 06-03-2021, 03:46 PM Thread Starter
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Quote:
Originally Posted by Bilko View Post
I forgot to ask an important question. Do the vibrations occur in normal driving or only when you apply the brakes

The tires are Bridgestone Turanzas.



The shaking only occurs when applying the brakes. Not at all when simply traveling along. Barely noticeable at 20-30 MPH. More so at higher speeds, and when exiting the highway after a long run, can be downright scary if you firget and put the brakes on hard. When I got off the highway after picking it up the first time and assuming it was fixed, I got a very rude awakening. Almost as bad as an old Wrangler's death wobble. At the slower speeds, it's not really shaking, so much as "slow down/drag more-slow/drag down less", etc., as you roll to a stop.



As I always anticipate my braking anyway, even without this problem, it's manageable for now, but obviously needs to be remedied.
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post #6 of 25 Old 06-03-2021, 03:55 PM
Bilko
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I am a Bridgestone fanboy because they make high-quality tires that meet and probably exceed my needs. I doubt these are going to be the issue.

Usually, the braking vibes increase when they are hot. My guess is poor-quality rotors and pads but you should also check if you have any leaks. if you have an oil or AT transmission cooler leak, the leaking fluids can be blown along the front driveshafts and contaminate the the brake pads.

Check out Youtube, changing the disks and rotors on a WK2 is really easy and only takes about 30mins. Focus on the front brakes because the rears are unlikely to cause the problems you are experiencing.
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post #7 of 25 Old 06-03-2021, 04:34 PM
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Given that he's had a couple competent techs changed rotors and pads, sounds like a couple times, and can't figure it out (techs that may not familiar with independent suspension Jeeps). I'm going to guess they would have noticed contamination on the rotors.... or pads... but that just may be me.

I had a set of rear calipers freeze/stick where the first indication was the brakes pulsing when stopping hot. The hotter the brakes the more pulsing. Lots of brake dust is a symptom of frozen or stuck calipers.

If you are sure its not calipers, rotors, or tires, then something is loose. Lug nuts, caliper bracket bolts, calipers installed wrong, bearings, ball joints, tie rods, bushings, crossmember bolts...
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I just got lost in thought. It was unfamiliar territory;
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #8 of 25 Old 06-03-2021, 04:53 PM Thread Starter
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Originally Posted by ColdCase View Post
Given that he's had a couple competent techs changed rotors and pads, sounds like a couple times, and can't figure it out (techs that may not familiar with independent suspension Jeeps). I'm going to guess they would have noticed contamination on the rotors.... or pads... but that just may be me.

I had a set of rear calipers freeze/stick where the first indication was the brakes pulsing when stopping hot. The hotter the brakes the more pulsing. Lots of brake dust is a symptom of frozen or stuck calipers.

If you are sure its not calipers, rotors, or tires, then something is loose. Lug nuts, caliper bracket bolts, calipers installed wrong, bearings, ball joints, tie rods, bushings, crossmember bolts...

I'm not sure of anything except what the first guy told me. He also said he checked out everything in the steering and suspension for anything obvious, and found nothing. I've always done my own brakes and had no troubles. The second guy is just going by what he thinks after test-driving it with me. He thought that one of the front rotors was hotter than the other. I just don't know which one of them to have work on it next.


I guess I'm superstitious about noticing it after picking the vehicle up from BJs with the new tires, but BJs says the tires are fine, and I don't see how a tire problem would show up only when braking.


No wheel bolts or nuts have been changed.
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post #9 of 25 Old 06-03-2021, 06:16 PM
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It just seems strange that a reputable repair shop would install parts a customer bought on Amazon. They have no way of knowing the quality of the parts yet the fact they install them would expose them to liability issues if they don't work. They must either have a very good insurance policy or don't give a F!!!
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post #10 of 25 Old 06-03-2021, 07:56 PM Thread Starter
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Quote:
Originally Posted by Bilko View Post
It just seems strange that a reputable repair shop would install parts a customer bought on Amazon. They have no way of knowing the quality of the parts yet the fact they install them would expose them to liability issues if they don't work. They must either have a very good insurance policy or don't give a F!!!
He's a one-man shop and it was my understanding ahead of time that he is willing to install supplied parts. I thought it odd, but as I said, he was well-recommended, and by a friend who runs a small one-man used car dealership. I retired to Maine from Massachusetts 4 years ago and have had to start building a new set of folks for maintenance and repair-type things.
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post #11 of 25 Old 06-04-2021, 06:46 AM
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Just some info (probably unrelated...)
Pulsing brakes can be 100% in spec, no out of round, no warping, no thickness issues. BUT there can be "hot spots" on the rotors. Basically parts of the surface are different hardness than others, so as it rotates it slips/grips/slips/grips with each rotation. This typically happens when braking hard to a stop, then sitting still. So the extremely hot rotor is covered partly by the pads, so that area cools slower then the exposed parts which can "work harden".

BUT you said that new rotors didn't change anything, so either someone is wrong about what they did, or something is off. Don't rule out a wheel that isn't seating correctly, or something bent like a caliper pin.
Also, have someone lean out the window and look at each wheel under breaking and see if any wobble is noticeable.

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post #12 of 25 Old 06-04-2021, 09:09 AM
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I have one thought for you, based on your description of when it happens. As you likely know, there's a common theory that some "warped rotors" are actually uneven brake pad deposits on the rotor, causing vibrations etc. during braking. Powerstop pads have a good reputation, but I also saw multiple comments about buying from Amazon...are you sure they actually are Powerstop? Poor pads could get hot enough to deposit and cause the vibration. Similar to what Overland described, but on the pad side, and when the pads are cold they could clean the rotors (a lot of the BMW guys do this for track days - run race pads which get hot and ablate evenly during the event, but scrape off the ablation on the cooler drive home. Then they can change the pads back to street pads without issue).

So maybe check by driving until you experience the vibration, then rolling straight into the shop?

Good luck!

Cheers

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post #13 of 25 Old 06-04-2021, 09:40 AM Thread Starter
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Quote:
Originally Posted by WK2Overland4X4 View Post
Just some info (probably unrelated...)
Pulsing brakes can be 100% in spec, no out of round, no warping, no thickness issues. BUT there can be "hot spots" on the rotors. Basically parts of the surface are different hardness than others, so as it rotates it slips/grips/slips/grips with each rotation. This typically happens when braking hard to a stop, then sitting still. So the extremely hot rotor is covered partly by the pads, so that area cools slower then the exposed parts which can "work harden".

BUT you said that new rotors didn't change anything, so either someone is wrong about what they did, or something is off. Don't rule out a wheel that isn't seating correctly, or something bent like a caliper pin.
Also, have someone lean out the window and look at each wheel under breaking and see if any wobble is noticeable.

The mechanic that can't figure it out said the new rotors didn't change anything, prompting him to remove them and check them on a lathe at a local machine shop. As they were good, he then replaced the aggressive pads and put on NAPA Premiums. Still no good.


I like the idea about hanging out the window to see what we can see. I had forgot doing just that 30 or more years ago on an old CJ-5, but it had huge tires that were easy to see....


Thanks for the reminder.
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post #14 of 25 Old 06-04-2021, 09:45 AM Thread Starter
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Quote:
Originally Posted by TXTrailhawk View Post
I have one thought for you, based on your description of when it happens. As you likely know, there's a common theory that some "warped rotors" are actually uneven brake pad deposits on the rotor, causing vibrations etc. during braking. Powerstop pads have a good reputation, but I also saw multiple comments about buying from Amazon...are you sure they actually are Powerstop? Poor pads could get hot enough to deposit and cause the vibration. Similar to what Overland described, but on the pad side, and when the pads are cold they could clean the rotors (a lot of the BMW guys do this for track days - run race pads which get hot and ablate evenly during the event, but scrape off the ablation on the cooler drive home. Then they can change the pads back to street pads without issue).

So maybe check by driving until you experience the vibration, then rolling straight into the shop?

Good luck!

Cheers

Thanks -- Those Powerstops are gone now. But when I had had them put on 6 months ago with the new Amazon-bought rotors, I did do the "break-in" as recommended. My wife was following me home in the JK and said it stunk pretty bad. And then the brakes were great for 6 months.



Still undecided on what to do. Maybe see if a Jeep dealer will diagnose it for me?
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post #15 of 25 Old 06-04-2021, 10:38 AM
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Quote:
Originally Posted by KeepOnTruckin View Post

I like the idea about hanging out the window to see what we can see. I had forgot doing just that 30 or more years ago on an old CJ-5, but it had huge tires that were easy to see....
.
Some here stick something like a GoPro camera on the body or frame. Its a good troubleshooting tool and you don't have to hang out the window.
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