Whacked Out Brakes / Speed Sensor?

[eric_rosenwald]

I bought my 2000 4Runner used, in May. The engine still sounds new! I had it inspected, and I was told the brakes were in great condition.

Not long after I got it, I noticed that at highway speeds, when I stepped on the brake pedal, a loud shimmy/vibration started that resonated through the whole car. I assumed it was an alignment, etc. issue. I had it aligned and had a front left tie rod end replaced -- The tech said that it wasn't about to fail and wasn't an urgent fix, but I got it replaced anyway. The brake/vibration problem was so occasional that it was impossible to tell if the vibration problem was solved. In general, it seemed to work. I did feel some vibration a few times though.

About a month later, I went on a long road trip. I was coming down a steep road from a 12,000ft mountain, and I completely forgot to put it in 2nd gear! The brakes had quite a workout, but like I said... There was plenty of life in them. When I got to the bottom of the mountain, I noticed that I had that same brake problem again, except this time it was more intense and loud. Then I noticed a bad smell. I pulled over immediately and noticed that the left rear wheel was stinking of something burning. I figured I had killed my brakes because it was so steep and I wasn't using engine braking.

So not long after, I took it into a shop. The guy showed me everything. It turns out the brakes were fine! What he noticed though was that the axle was leaking oil... He said that it's a common problem on 2000 T4Rs -- they need new rear axle seals. He had a brilliant explanation for the smell. Considering the fact that I was using the brakes so much, the axle/wheel/brake area was getting very hot. Because there was a leak and a widespread film of half-burnt oil had developed in the area, it started to burn a little when the brakes got hot. No problem with the brakes at all. He said the seal issue wasn't urgent, either.

A few thousand miles down the road, I got the rear seals/whatever fixed in the axle. It was good to go. But not long after, I noticed that when I was idling, and I let off the brake just as I started to roll, the entire vehicle started shaking violently. I stopped immediately and it would go away. When someone else drove it, I noticed that the rear left tire (the one where oil was leaking out a lot into the brake area) locked up! The other wheels were rolling, but that tire was dragging. It was going about 2mph when this happened, so nothing major resulted. I assumed it was some kind of transmission issue. This violent shaking would happen ONLY when I had just started up the 4Runner, at that slow idle speed. There was no problem, otherwise. When I finally got home, I took it in to several shops to get it inspected... and see if there was a transmission problem. Because it was so irregular (didn't do it every time I started up... maybe every 10th time), they said "come in when you can replicate the problem". It was frustrating, but I don't blame them. They couldn't see any problems.

So I looked up the issue on the forum. Based on what others said, I had a theory that when that differential oil (or whatever oil) was leaking out of the axle and covered the brake area, it left a film or goop of semi-burnt oil. Getting the new seals worked fine, but in the process, the guys must not have cleaned off all of that gunk that was left behind, and ended up leaving some that interfered with the speed sensor. When the 4Runner started to roll at idle, it thought that the rear left wheel wasn't spinning, and activated ABS. Keep in mind, I had no engine lights or ABS lights throughout any of this. The reason that the ABS light didn't come on was because it didn't think there was a problem -- it simply thought that the left rear wheel wasn't spinning, and freaked out by kicking in ABS. So a few days ago I took it into a shop to have the brakes, and the brake area / axle area cleaned, and told them to clean the ABS sensor. I don't think he paid much attention to the story, though. I took it out of the shop and there wasn't a problem. My theory was confirmed. It was gunk that was covering the ABS wheel speed sensor.

Then... something new came up after a few days. I have to steer slightly to the right, and that left side (I think the problem left rear area) seems to be extremely touchy with the brakes. Super sensitive. I know I don't have an alignment problem because it was absolutely spot-on perfect before this (when he cleaned it, he didn't touch the front wheels). After cleaning it, the original violent low-speed ABS activation stopped. But now it's something new.

I'm sick of dealing with this, and I'm considering just taking it into the dealership -- even though it's more expensive. An easy theory would be that the speed sensor is shot, but if that were the case, why did the super-annoying low-speed ABS activation problem stop, after it was supposedly cleaned? Also -- why is the 4Runner wanting to tug to the left (especially when I brake) if it just got cleaned? Shouldn't there be less friction on the left side? I have to steer slightly to the right at all speeds, but it tugs even more to the left when I brake.

Any thoughts or suggestions? Thank you for being willing to read this long post!

 

[ajonesnv]

These trucks are notorious for warping rotors, hence the Tundra Brake Upgrade being so popular.

There could be a combination of issues. Possibly warped rotors and the lines need to be bled. If the rear seals were done then the brake lines were removed, if the lines weren't bled after the fact there could be air in the line, which will cause squishy and pulsating brakes. Also, if the seals were leaking the shoes have to be replaced...they can't be cleaned and reused, which will add to the issues.

Good luck

 

[eric_rosenwald]

These trucks are notorious for warping rotors, hence the Tundra Brake Upgrade being so popular.

There could be a combination of issues. Possibly warped rotors and the lines need to be bled. If the rear seals were done then the brake lines were removed, if the lines weren't bled after the fact there could be air in the line, which will cause squishy and pulsating brakes. Also, if the seals were leaking the shoes have to be replaced...they can't be cleaned and reused, which will add to the issues.

Good luck

Thanks!

Do you think the fact that it could be a combination of issues means that it's a good idea to go to the dealership, where they have more knowledge and can look at the problem in a more detailed, thoughtful way (the way you just did)? I rarely ever go to a dealership for the obvious price reasons, but is this a good situation to do that?

 

[ajonesnv]

Thanks!

Do you think the fact that it could be a combination of issues means that it's a good idea to go to the dealership, where they have more knowledge and can look at the problem in a more detailed, thoughtful way (the way you just did)? I rarely ever go to a dealership for the obvious price reasons, but is this a good situation to do that?

No, I would just start "eating the elephant one bite at a time." Personally I would bled the brakes first. (Rear Passenger, Rear Driver, Front Passenger, Front Driver.)

Then would check with who did the seals to determine if the shoes were replaced. If not do that next.

As far as the front brakes go, I would do the Tundra brake upgrade...you will be hard pressed to ever warp another rotor again. The dealership won't do this, so it is up to you. There are a couple threads that are VERY informative on this subject, i.e. this one: http://www.toyota-4runner.org/3rd-g...ements-231mm-13wl-tundra-calipers-rotors.html

Edit: Based on your avatar you would have to do the 199mm upgrade and not the 231mm due to the type of wheels you have.

 

[eric_rosenwald]

No, I would just start "eating the elephant one bite at a time." Personally I would bled the brakes first. (Rear Passenger, Rear Driver, Front Passenger, Front Driver.)

Then would check with who did the seals to determine if the shoes were replaced. If not do that next.

As far as the front brakes go, I would do the Tundra brake upgrade...you will be hard pressed to ever warp another rotor again. The dealership won't do this, so it is up to you. There are a couple threads that are VERY informative on this subject, i.e. this one: http://www.toyota-4runner.org/3rd-g...ements-231mm-13wl-tundra-calipers-rotors.html

Edit: Based on your avatar you would have to do the 199mm upgrade and not the 231mm due to the type of wheels you have.

By the way, I installed Billstein 4600s and OME coils in the rear since the last photo (my new one is updated).

Thanks for the advice!

As far as the pulling to the right (as if there were an alignment problem, which there isn't), how would that be happening? Is that where a warped rotor might be to blame, or the shoe is touching something it shouldn't? It just seems so weird that I traded in one problem for another. It's interesting to me that it tugs even more when I hit the brakes. I had never heard about the air bubble thing.

I'm wondering if it's had the same subtle problem for the entire time I've had it (since May... the original high-speed unnecessary ABS activation). If I change things around (lift kit, new seals, got rear brakes cleaned) it changes the behavior, but it ultimately has one root cause that I haven't discovered. I don't know much about brake systems, but I sure hope bleeding it like you recommended works.

I'm taking it in first thing tomorrow, and telling them to do exactly what your advice is. I'm noticing more guys at shops saying, "did you check online for any possible causes?" I'll also call the guys in Seattle that did the seals. I hate these phantom problems.

 

[ajonesnv]

By the way, I installed Billstein 4600s and OME coils in the rear since the last photo (my new one is updated).

Thanks for the advice!

As far as the pulling to the right (as if there were an alignment problem, which there isn't), how would that be happening? Is that where a warped rotor might be to blame, or the shoe is touching something it shouldn't? It just seems so weird that I traded in one problem for another. It's interesting to me that it tugs even more when I hit the brakes. I had never heard about the air bubble thing.

I'm wondering if it's had the same subtle problem for the entire time I've had it (since May... the original high-speed unnecessary ABS activation). If I change things around (lift kit, new seals, got rear brakes cleaned) it changes the behavior, but it ultimately has one root cause that I haven't discovered. I don't know much about brake systems, but I sure hope bleeding it like you recommended works.

I'm taking it in first thing tomorrow, and telling them to do exactly what your advice is. I'm noticing more guys at shops saying, "did you check online for any possible causes?" I'll also call the guys in Seattle that did the seals. I hate these phantom problems.

The pulling problem can definitely be related to the brakes, especially since you say it gets worse when you brake. Could be a failing caliper or rear cylinder. If you end up doing the Tundra Brake Upgrade you have to replace the front calipers anyways.

Also, when you got your seal replaced did they do anything with the rear bearing. Typically the reason the seals go is because of a bad bearing, the wobble ruins the seal. If the shop didn't charge you 600-800.00 then he didn't do that and a bad bearing will just ruin another seal, which will put you back into needing new rear shoes and so on.

If you are going to take it in, have them inspect the rear for another leaking seal, a bad bearing, and do a thorough inspection on the rear brakes. I would definitely have the shoes replaced if they are going to bleed the lines.

One thing is for sure, gear oil will ruin the shoes.

 

[eric_rosenwald]

The pulling problem can definitely be related to the brakes, especially since you say it gets worse when you brake. Could be a failing caliper or rear cylinder. If you end up doing the Tundra Brake Upgrade you have to replace the front calipers anyways.

Also, when you got your seal replaced did they do anything with the rear bearing. Typically the reason the seals go is because of a bad bearing, the wobble ruins the seal. If the shop didn't charge you 600-800.00 then he didn't do that and a bad bearing will just ruin another seal, which will put you back into needing new rear shoes and so on.

If you are going to take it in, have them inspect the rear for another leaking seal, a bad bearing, and do a thorough inspection on the rear brakes. I would definitely have the shoes replaced if they are going to bleed the lines.

One thing is for sure, gear oil will ruin the shoes.

I found the receipt and these are the parts:
seal, axle
bearing, rear axle
retainer, rear wheel bearing
seal, rear outer wheel

It looks like they didn't change the shoes!

When I had the brakes cleaned a few days ago, they said they looked fine. Are bad shoes easily visible?

I'm certain a good bit of gear oil got all over the place... They may have cleaned the brakes assembly a few days ago, but if they were covered in half-burnt, stinking gear oil, I see why the shoes would be bad. Could bad shoes cause that pull, or is that only going to be caused by a caliper/drum issue like you said?

 

[ajonesnv]

I found the receipt and these are the parts:
seal, axle
bearing, rear axle
retainer, rear wheel bearing
seal, rear outer wheel

It looks like they didn't change the shoes!

When I had the brakes cleaned a few days ago, they said they looked fine. Are bad shoes easily visible?

I'm certain a good bit of gear oil got all over the place... They may have cleaned the brakes assembly a few days ago, but if they were covered in half-burnt, stinking gear oil, I see why the shoes would be bad. Could bad shoes cause that pull, or is that only going to be caused by a caliper/drum issue like you said?

It seams unlikely that just bad shoes will cause that kind of pull, but yes if gear oil got on them they will soak up the oil like a sponge and won't clean out.

If the pull is brake related then my best guess, without having driven it, is that the caliper or rear cylinder isn't releasing when you let off the brake and overcompensating compared to the other corners when you apply the brake.

Wish you were a tad closer, I'd come and help you out with this.

 

[eric_rosenwald]

It seams unlikely that just bad shoes will cause that kind of pull, but yes if gear oil got on them they will soak up the oil like a sponge and won't clean out.

If the pull is brake related then my best guess, without having driven it, is that the caliper or rear cylinder isn't releasing when you let off the brake and overcompensating compared to the other corners when you apply the brake.

Wish you were a tad closer, I'd come and help you out with this.

Should I definitely replace those shoes, or is it possible to inspect them to see if they're OK?

How would they diagnose if it's a caliper issue? What would they be looking at? Is it the kind of thing where you can spot a problem visually, some kind of test, or by touch? Or is it a situation where you want to change/fix them because it seems like the most likely thing, without there being direct evidence of it?

Either way, considering that it might be that... do you still think replacing the shoes and bleeding the brake lines is a good first start?

Thanks man, you're equipping me with all of the knowledge I need when I go down there tomorrow

 

[ajonesnv]

Should I definitely replace those shoes, or is it possible to inspect them to see if they're OK?

How would they diagnose if it's a caliper issue? What would they be looking at? Is it the kind of thing where you can spot a problem visually, some kind of test, or by touch? Or is it a situation where you want to change/fix them because it seems like the most likely thing, without there being direct evidence of it?

Either way, considering that it might be that... do you still think replacing the shoes and bleeding the brake lines is a good first start?

Thanks man, you're equipping me with all of the knowledge I need when I go down there tomorrow

Yes on the shoes.

Bleed the line before you replace any calipers though, because if there is air or a lack of fluid it can cause the calipers to act up, which might cause your problem.

--If it is a bad caliper or rear cylinder you can typically tell by a visual & function inspection. Those that you have looking at it should be able to identify any problems.--

If it were my truck step 1 would be replacing the shoes and bleeding the brake lines. Step 2 would be doing a front brake job, but like I said in the past few posts, I would do the tundra upgrade to avoid future (inevitable) rotor warping.

 

[JohnMc]

The axle locking up is strange. I'd suspect a (badly) failing axle bearing - the leaking oil can wash out the bearing's grease, then when the oil stops (seal fixed*) the bearing goes dry, then starts to fail after a while. But it likely would be noisy, not come and go with such grace, plus they replaced it.

Oil on the brake shoes isn't good, it's bad, no doubt about it. But I have a hard time picturing ways that oil soaked brake shoes would make the brake grab on that wheel.

I do know that leaking brake fluid will make a drum brake really 'grabby' - very prone to locking up and sliding even under light braking when it's leaked inside the drum and gotten everything wet.

But that still wouldn't explain why this is holding and locking when the brakes are released. I'd almost suspect something with the brake shoes wasn't reassembled properly - that a shoe isn't properly being pulled back away form the drum by the spring, and occasionally it just gets stuck outward against the drum - by the drums movement. Drum brake shoes are commonly configured like that to add a certain degree of self activation. The springs are there to prevent them from engaging like that until the pedal is applied, but perhaps a spring is out of place, or an incorrect spring (too weak) was used?

I'd say that the ABS system won't do that, can't do that, but the ATRACS system could possibly do that. But that's not on an '00, is it? I thought that was 01-02 model years. The ABS braking only system on the earlier cars won't activate until the pedal is down. And even then on a braking only system, it will only bleed down the pressure on a wheel, not pump it up. Newer systems using the brakes for traction control and vehicle dynamics (preventing spins, etc) can do that, but that's a significant hardware/software enhancement.

* - PS: Many times, the seal is leaking because of a plugged/stuck breather. Sure, the seal is leaking, but it's still good.

 

[eric_rosenwald]

problem solved!

The axle locking up is strange. I'd suspect a (badly) failing axle bearing - the leaking oil can wash out the bearing's grease, then when the oil stops (seal fixed*) the bearing goes dry, then starts to fail after a while. But it likely would be noisy, not come and go with such grace, plus they replaced it.

Oil on the brake shoes isn't good, it's bad, no doubt about it. But I have a hard time picturing ways that oil soaked brake shoes would make the brake grab on that wheel.

I do know that leaking brake fluid will make a drum brake really 'grabby' - very prone to locking up and sliding even under light braking when it's leaked inside the drum and gotten everything wet.

But that still wouldn't explain why this is holding and locking when the brakes are released. I'd almost suspect something with the brake shoes wasn't reassembled properly - that a shoe isn't properly being pulled back away form the drum by the spring, and occasionally it just gets stuck outward against the drum - by the drums movement. Drum brake shoes are commonly configured like that to add a certain degree of self activation. The springs are there to prevent them from engaging like that until the pedal is applied, but perhaps a spring is out of place, or an incorrect spring (too weak) was used?

I'd say that the ABS system won't do that, can't do that, but the ATRACS system could possibly do that. But that's not on an '00, is it? I thought that was 01-02 model years. The ABS braking only system on the earlier cars won't activate until the pedal is down. And even then on a braking only system, it will only bleed down the pressure on a wheel, not pump it up. Newer systems using the brakes for traction control and vehicle dynamics (preventing spins, etc) can do that, but that's a significant hardware/software enhancement.

* - PS: Many times, the seal is leaking because of a plugged/stuck breather. Sure, the seal is leaking, but it's still good.

So I took it in... The guys who did the work said that they didn't notice anything. They seemed like they just didn't want to accept that there was a new problem ONLY after they did work.

So I took it to Brake Masters. They were cool about everything. I told them to change the shoes, even if they didn't think it was necessary. Both shops said, "If the shoes aren't wet/oily, then they don't need to be replaced. It looks like the axle seal leak was minor. Shoes don't need to be replaced in this circumstance." No one seemed to understand that after axle work like that, you need to change them.

So I told them to do it anyway. After I left the shop, the brakes felt much better, but the alignment was still having that same problem (steering to the left). So I took it to a third shop (Big O Tires). They were actually attentive! There are a lot of issues with my problem, and they were patient. They clearly enjoyed the diagnosis problem. It was a challenge for them. So the alignment WAS bad! They fixed it. It must have been a complete coincidence, or maybe some of the brake problems did something to throw it out. I don't know.

But either way, the shoe replacement was key. The truck brakes better than it ever has. It's got this velvety smooth feel, but it's still firm. It's hard to describe, other than 'perfect'.

I ended up finding a great new shop to go to. The owner is awesome, and he hires SMART people who actually enjoy the diagnosis part. Everyone mechanic should, but unfortunately most don't. So many mechanics fail to fully understand that a vehicle is a complex system of feedback loops. They don't realize that they make all kinds of false assumptions. This one guy said, "well, if the ABS light doesn't come on, there's no ABS problem." I said, "yeah, but what if the reason the ABS light doesn't come on is that the computer doesn't think there's a problem. Just because there isn't a clear indication of a problem doesn't mean the problem doesn't exist." He just stared blankly at me.

So I really wanna say thanks for the help and wisdom. Your advice was spot-on. The problem is 100% solved, and she's back to her usual, almost-brand new performance.

 

[ajonesnv]

So I took it in... The guys who did the work said that they didn't notice anything. They seemed like they just didn't want to accept that there was a new problem ONLY after they did work.

So I took it to Brake Masters. They were cool about everything. I told them to change the shoes, even if they didn't think it was necessary. Both shops said, "If the shoes aren't wet/oily, then they don't need to be replaced. It looks like the axle seal leak was minor. Shoes don't need to be replaced in this circumstance." No one seemed to understand that after axle work like that, you need to change them.

So I told them to do it anyway. After I left the shop, the brakes felt much better, but the alignment was still having that same problem (steering to the left). So I took it to a third shop (Big O Tires). They were actually attentive! There are a lot of issues with my problem, and they were patient. They clearly enjoyed the diagnosis problem. It was a challenge for them. So the alignment WAS bad! They fixed it. It must have been a complete coincidence, or maybe some of the brake problems did something to throw it out. I don't know.

But either way, the shoe replacement was key. The truck brakes better than it ever has. It's got this velvety smooth feel, but it's still firm. It's hard to describe, other than 'perfect'.

I ended up finding a great new shop to go to. The owner is awesome, and he hires SMART people who actually enjoy the diagnosis part. Everyone mechanic should, but unfortunately most don't. So many mechanics fail to fully understand that a vehicle is a complex system of feedback loops. They don't realize that they make all kinds of false assumptions. This one guy said, "well, if the ABS light doesn't come on, there's no ABS problem." I said, "yeah, but what if the reason the ABS light doesn't come on is that the computer doesn't think there's a problem. Just because there isn't a clear indication of a problem doesn't mean the problem doesn't exist." He just stared blankly at me.

So I really wanna say thanks for the help and wisdom. Your advice was spot-on. The problem is 100% solved, and she's back to her usual, almost-brand new performance.

Very glad to hear! Simple diagnosis can get out of hand quick if you are not dealing with experienced people, and frankly, these Toyotas have some very specific design items that are not as common as other vehicles. Essentially, a mechanic that doesn't see many Toyotas will typically under or overestimate the problem.