dragging break (1 Viewer)

[Stecz]

I have a strange issue on my LX (305k miles)
the left front break is dragging. I know this because it wore out the pads on that size, twice as fast as the right, it also has a bunch of brake dust on the left wheel, but not the right. I also used an IR thermometer and when I got back from a short drive, the left rotor was about 165 degrees and the right one was more like 115.

It doesn't pull to the left at cruise, or while braking, so it's not horrible.

I figured the caliper was sticking, so I replaced the left caliper, but it's still dragging.

Any good ideas on how to troubleshoot? The other rotors are even temps, so it's just the left front. That makes me think that it's not the master cylinder. ABS pump seems unlikely given that everything works. That leaves flexible brake lines?

Any ideas?
thanks
John S.

 

[Stecz]

I can't believe I misspelled "Brake" in the title.

 

[jpoole]

Since it's just one wheel I agree with your thinking so far. A possible test that may be helpful could be to:

• lift the one wheel in question after chocking the other wheels and shifting the transfer case into neutral so that the wheel in question can spin freely
• depress the brake pedal until the brakes on that wheel start to drag/bind with the pedal released
• crack the brake bleeder or brake line on that wheel (briefly to avoid getting much air into the system) to see if releasing the hydraulic pressure removes the dragging/binding (will need to rebleed after this)
• if the dragging/binding doesn't seem to be caused by hydraulic pressure inspect/wiggle/etc. the pads/pins to see if there is mechanical binding on the slide pins or caliper sticking.

Once you figure out if the binding is hydraulic vs. mechanical you can go from there. You can retest the hydraulic binding further up the circuit to figure out if or which hose is causing this or if it's another part of the system causing the pressure retention. Unless your brake hoses are old and need replacing I'd figure out what's causing the problem before I started throwing more parts at it since you have to do bleed cycles when you change parts/etc.

Did you reuse the old slide pins on the new calipers? I've seen crusty slide pins cause brake drag also. Wire brush and then a light grease coat can resolve that. I've also seen collapsed inner hoses cause this issue before and have had weird binding from calipers and master cylinders which is why I'd do some testing to track it down as a next step.

 

[Stecz]

I'm sure the brake hoses are old, I assume they are original from 1997, so 23 years and 300k miles.
I'll run this test shortly and see what I find.

The brake caliper is new, with new slide pins, but I will take them out and grease them just for completeness. (after the test)

The other thing I thought about is, if there is play in the hub (wheel shakes), that could be it also. I didn't check that yet.

 

[jpoole]

Good point on bearing looseness. That's really common with these it seems probably in part due to the FSM torque procedure. You can read up on this forum to learn more about front wheel bearing torque in case you want more info and here is one of many discussions on the topic:

Inner Nut Torque Front Wheel Bearing Preload?

I have read anywhere from 10 ft/lbs to 25+ ft/lbs for the preload of front inner wheel bearing nut. Is there a correct setting or are people just doing different torque setting for personal preferences?

forum.ih8mud.com

Google Search:

fzj80 front wheel bearing torque site:forum.ih8mud.com

 

[Tanner H]

The brake caliper is new, with new slide pins, but I will take them out and grease them just for completeness. (after the test)

I could be wrong but I dont believe there are any slide pins in the front calipers, just the four pistons that press on the back of the pads.

Could be a tight bearing causing the drag. That wouldnt explain your uneven pads...but maybe you had both a sticky caliper and a bad bearing.

I'd lift the front and remove the wheel. try and rotate the brake rotor and take note of how much resistance there is. then remove the caliper and carefully sit it on top of the hub or hang it up. then rotate the rotor with your hand to see if there is a significant change in resistance. if the rotor rotates easily then you are still having a caliper issue (might try bleeding again since thats free).

if the rotor still has a lot of resistance with the caliper removed then sounds like a tight bearing.

 

[Stecz]

I don't think it's a tight bearing. The temp on the left hub was within 1 or 2 degrees of right hub, but the temp difference between the rotors was substantial.
I'm going to go troubleshoot now, I'll post what I get.

 

[Stecz]

ok, did some troubleshooting....

No play in the hubs on either side.

removed both front wheels, tried to get a feeler gauge in between the rotor and pad, couldn't get the smallest feeler gauge in on the good side or bad. Inconclusive

I pressed hard on the brakes, with the engine running and neither side seem to drag the pads much. I then pressed hard on the brakes again and cracked the bleeder and no fluid squirted out. Seems like it's not hydraulic.

I then pulled the pads, noticed 2 things. One there was brake dust built up on the anti-rattle spring (new), but only where the interface for the outboard pad and rotor is. None where the inner pad and rotor interface is. HMMM.

I pulled the pads and noticed that the paint(?) on the edge of the outboard pad backing plate (where it slides on the sides of the caliper) seemed like it had been scraping, not just rubbing. On the outboard pad, didn't notice that. So I filed a bit off of the edges of the pads, then greased the edges, the pins and the anti-rattle spring where it rubs on the pads.

A quick test drive indicates that maybe I fixed it. I typically have a very distinct rubbing noise right after I brake, when the brakes are cool, but I didn't hear it.

I'll have to take a longer stop and go drive and check the temps.

I'm skeptical this is the fix since I was having this problem with the old set of pads in the old caliper, new pads (same powerstops) in the old caliper and the new pads in a new caliper. But still could be the problem.

 

[Stecz]

I could be wrong but I dont believe there are any slide pins in the front calipers, just the four pistons that press on the back of the pads.

Could be a tight bearing causing the drag. That wouldnt explain your uneven pads...but maybe you had both a sticky caliper and a bad bearing.

I'd lift the front and remove the wheel. try and rotate the brake rotor and take note of how much resistance there is. then remove the caliper and carefully sit it on top of the hub or hang it up. then rotate the rotor with your hand to see if there is a significant change in resistance. if the rotor rotates easily then you are still having a caliper issue (might try bleeding again since thats free).

if the rotor still has a lot of resistance with the caliper removed then sounds like a tight bearing.

When I read your message the first time, I was thinking wrong. I was thinking of the retention pins as slide pins, but you are right, the caliper doesn't slide together like a lot of calipers, it's just the 4 pistons. However, I did grease the retention pins where they slide through the holes on the caliper.

 

[jpoole]

Right,

I was probably unclear but we are on the same page now. The calipers/pads work differently and terminology varies between front/rear calipers on the 80s and from one car to another but the general concepts are the same. Mechanical stickiness can lead to brakes dragging because they can't release and depending on where the sticking is you may also see uneven pad wear, get weird pedal feel, etc. Hydraulic pressure can also cause brake drag, sticky caliper pistons and bearing issues possibly also...

In any case it can be helpful to break down the larger possible source areas and test to rule out a large chunk of potential issues at a time until the scope of possible issues is smaller. Esp. with brakes if you can confidently avoid the rabbit trail of premature hydraulic component replacement and system bleeding then you'll get your issue resolved much more quickly.

 

[jpoole]

Also, the pads slide on the pins and the pins don't really slide through the caliper during operation on the front calipers on these. That means that cleaning (hard with wire brush to remove the chunks) the whole length of the pin, particularly the areas that contact the tabs on the brake pads and applying high-temp brake grease lightly to the pins will be most effective. You can inspect/test to make sure that the pins are smooth and not corroded/etc. in a way that may lead to pad binding on them. If you see irregularities new pins may be in order.

 

[Stecz]

Also, the pads slide on the pins and the pins don't really slide through the caliper during operation on the front calipers on these. That means that cleaning (hard with wire brush to remove the chunks) the whole length of the pin, particularly the areas that contact the tabs on the brake pads and applying high-temp brake grease lightly to the pins will be most effective. You can inspect/test to make sure that the pins are smooth and not corroded/etc. in a way that may lead to pad binding on them. If you see irregularities new pins may be in order.

The pins are brand new, so they are smooth. I did lightly grease them.

I went on a drive this evening and measured temps when I got back and the left and right were close in temperature. Previously, the left was 45% higher.

I'll have a better sample tomorrow and I can decide if I think it's really fixed.

 

[Stecz]

I forgot to post the above just now, I should have editted it. I went on a longer stop and go drive today and it seems pretty even, I've never measured brake temperatures like this, so I'm not sure what to expect as far as a normal variance, but the right side rotor was 140ish, the left was maybe 155ish.

The outside of the calipers were pretty even at about 80, so I'm not heat soaking the left brake.

So it may not be perfect, but it's much better and it seems to be mechanical.

 

[jpoole]

I'm glad you were able to get such a big improvement so quickly.

Do you think this is what made the improvement:

"So I filed a bit off of the edges of the pads, then greased the edges"​

If so it seems like the powerstop pads you were and are running may not be a perfect fit for the calipers you had and have now. Care to post up a picture of the pads or more info on them for future reference in case others run into this?

 

[jonheld]

tried to get a feeler gauge in between the rotor and pad, couldn't get the smallest feeler gauge in on the good side or bad.

Disk brake pistons do not retract when you release the brake pedal. The pads are always resting on the rotors.

 

[Stecz]

Disk brake pistons do not retract when you release the brake pedal. The pads are always resting on the rotors.

I have always heard that the pistons retract them a tiny bit, and of course they get pushed back based on the runout of the rotor (which should be really small)
But I agree with you based on my feeler gauge experiment.
I'm going to do some more temperature tests and make sure I'm happy that I resolved the issue by filing down the edge of the backing plate.

 

[Stecz]

I'm glad you were able to get such a big improvement so quickly.

Do you think this is what made the improvement:

"So I filed a bit off of the edges of the pads, then greased the edges"​

If so it seems like the powerstop pads you were and are running may not be a perfect fit for the calipers you had and have now. Care to post up a picture of the pads or more info on them for future reference in case others run into this?

Sure. I was thinking I should have made a video when I did the initial troubleshooting. I guess I'm not much of a youtuber.

I'll get some pics and write up a quick article.

 

[jonheld]

I have always heard that the pistons retract them a tiny bit,

While there is a very small amount of negative fluid pressure when you release the pedal (as evidenced by doing a fluid flush into a bottle), it is nowhere near enough to move a single piston. Basically is it pressure on/off. Assuming a flat rotor, the movement of full brake pressure to no pressure would be measured in microns.
If pistons retracted even a little bit, it would yield a very soft/ineffective pedal.

 

[jpoole]

As I understand it the retraction is not the result of the fluid/hydraulics but of the seal. The page below and picture I grabbed from it supports this:

Brake Piston Seals Brake Drag and Pull

Sticking brake caliper piston seals cause a vehicle to pull to one side. This seal retracts the piston into its bore providing clearance between the brake rotor and the brake pad.

www.freeasestudyguides.com

 

[jpoole]

Interestingly they seemed to have installed the pistons in the calipers backwards in that diagram