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Brake Issue (Pedal Fade)

11K views 21 replies 12 participants last post by  Blown383 
#1 · (Edited)
Hey guys,

Not new to the FJ and been lurking here for a few years. I'm having a braking issue that recently popped up. Here's my setup:

I'm running a Dirt King LT setup +3.5" on a 2012. Kings at all four corners. With the long travel setup I installed extended SS brake lines. All was good after the install until just recently. I am getting some major brake pedal fade when I make a hard, LEFT TURN ONLY. I can replicate it every time. Low speed, u-turn or turning into a parking space. I loose about 80% of my pedal immediately after making the turn and as soon as I hit the pedal a second time it's back to normal. Everything is normal under all other driving conditions.

Here is what I've already done:

The entire brake system has been bled per Toyotas specs! Brake lines, accumulator pump, and master cylinder solenoid have all been bled using an intelligent tester (toyota scan tool). There's no air in the system. There are no kinks in the lines when turning to full lock in either direction.

All sensors have been checked and are functioning correctly. Throwing no codes! YAW sensor has been zero calibrated. Speed sensors were logged during diagnostics and are functioning properly.

Hub assembly, axle nut, brake calipers, brake lines and all suspension components are torqued to spec.

Wheel bearings are good. Nothing wandering around up front that could possibly collapse the caliper while turning.

I've been racking my brain for two weeks trying to get this resolved. Anyone here ever run into a similar situation?
 
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#2 ·
Have you checked to see if any calipers have seized pistons in them? It's a known issue. Typically the bottom piston.
 
#4 ·
you have checked everything!! it sounds like the issue some have with a panic stop, but yours is left turn only. you can not see everything all the time in a scan tool either, rust or corrosion on a sensor or reluctor?? chevys have an issue like this and it activates the abs, you can not see it, it just does it, good luck!
 
#5 ·
Nos2Fly -

Can you clarify exactly what you mean by " I am getting some major brake pedal fade" and "I loose about 80% of my pedal"?

"Brake fade" is typically what happens when pad material becomes grossly overheated, and its coefficient of friction is reduced. The pedal is hard, but braking effect is severely reduced. Direction of turn during braking doesn't affect "fade".

When you experience this:
1. Does the brake pedal suddenly go "hard" (loss of hydraulic boost)?
2. Does the brake pedal suddenly go "soft", and have increased travel?
3. Does this happen on paved or other high-traction surfaces, or only on low-traction surfaces, or on all surfaces?
4. When you say you "lose about 80% of your pedal", what exactly do you mean?
5. Do you detect any hint of ABS actuation when this happens?
6. Is ride height carefully matched at L and R front?
7. Do you have a lot of extra weight on the front end: aftermarket bumper, winch, 2nd battery, etc.?
8. When you say "turning left", is this a gently. dog-on-the-front-seat turn, or is this an abrupt, sliding or tire-squealing turn?
9. Likewise what level of braking is taking place: gentle deceleration, or near-max slowdown?
 
#8 · (Edited)
Nos2Fly -

Can you clarify exactly what you mean by " I am getting some major brake pedal fade" and "I loose about 80% of my pedal"?

"Brake fade" is typically what happens when pad material becomes grossly overheated, and its coefficient of friction is reduced. The pedal is hard, but braking effect is severely reduced. Direction of turn during braking doesn't affect "fade".

When you experience this:
1. Does the brake pedal suddenly go "hard" (loss of hydraulic boost)?
2. Does the brake pedal suddenly go "soft", and have increased travel?
3. Does this happen on paved or other high-traction surfaces, or only on low-traction surfaces, or on all surfaces?
4. When you say you "lose about 80% of your pedal", what exactly do you mean?
5. Do you detect any hint of ABS actuation when this happens?
6. Is ride height carefully matched at L and R front?
7. Do you have a lot of extra weight on the front end:b aftermarket bumper, winch, 2nd battery, etc.?
8. When you say "turning left", is this a gently. dog-on-the-front-seat turn, or is this an abrupt, sliding or tire-squealing turn?
9. Likewise what level of braking is taking place: gentle deceleration, or near-max slowdown?
FJtest,
I guess brake fade was a bad description. What I'm experiencing is the pedal suddenly goes soft and an increase in travel. To me it seems like low pressure from the accumulator pump but as soon as I hit the pedal a second time it's back to a normal pedal. I've noticed it mostly at low speeds, under normal driving conditions and on paved and dirt roads. The pedal will go soft and not firm up until it almost engages the ABS. About 80% of the pedal travel. It never engages the ABS. All of this is under normal braking conditions.

Don't know if this matters or not but the first time I had really noticed the issue it was after I had to do an emergency braking maneuver getting onto the freeway. Everyone decided they needed to stop at the end of the ramp before they merged. It was a hard braking effort and the ABS was engaged. Pedal felt normal during the event.

Let's talk ride height for a second, drivers side is lower than the passanger side but preload is equal on both sides. Drivers side is right at an inch lower than the passanger side. Funny thing with the LT setup is it never sits at the same ride height twice and goes down the road pretty damn level. I'm also running a DO flat top bumper with no winch. So not an extreme amount of added weight up front.

So when you ask "Is the ride height carefully matched at L and R front" what are you thinking? This is really the only thing that sticks out at me from your questions that I hadn't really thought much about.

Thanks everyone. Some brainstorming is what I need from someone on the outside. Look at it too long and everything looks the same.
 
#6 ·
Wow, that really is a strange one. I can see that from your description that you have pretty much looked at everything. Are all of the brake related components well out of harms way up front through the entire steering arc right to left? I'm thinking like maybe a brake line or ABS sensor wire might be getting pinched or stretched during that hard left turn causing the brake system to modulate and cause the issue/symptoms you are having.

In my limited knowledge of the system, if an ABS sensor wire loses continuity during the hard turn, the system will see the signal loss from a wheel and activate as if the wheel has locked. Once you turn back straight the wire might touch again and act as if all is normal. It could be a wire on either side of the rig, perhaps not just the left side. Perhaps the wire was damaged internally during work or mods to the suspension, and the problem is not visible (or barely visible). Zip ties can sometimes cause damage to a wire internally that shows up as a problem later. I know that when I went to the 4130 UCAs on my FJ, the ABS wires no longer had a place to bolt the stock wire guides, and I used zip ties to secure them. I had to slide the protective wire sheath to a different place along the wire to protect it properly.

Again, that's a strange one indeed. Lots of luck with it! Oh, and please let us know what you find that fixes it. :bigthumb:
 
#11 ·
Had a similar issue & my Rt front wheel speed sensor was dirty due to the wheel bearing coming apart. I would check the wiring as suggested & remove & clean the sensors with contact cleaner. After I rebuilt my front end. I was tepid driving away from my house as i was unsure if i had fixed the issue . Within 100yards problem went away. Also had long pedal travel but firm no air, no codes, either. I feel pretty confident that you have a bad sensor. Look on Ebay that finally have these sensors that are affordable when I had this issue, 250$ from Toyota & 125$ rock Auto.
 
#15 ·
Still having the same issue. Still no codes and only happens when I turn left but it has to be a sharp left turn with the wheel almost at full lock. I've been over this thing multiple times and can't for the life of me figure out what is going on. The one and only thing I haven't done is swap out the wheel sensors but in theory they should be eliminated by disconnecting at the booster which I've done and the results are the same. I've pulled the wheel sensors and he hubs to clean them with no change. It sucks for sure! Hopefully I'll get it figured out or someone else will.
 
#16 ·
Thanks for updating. Just by the nature of the problem I think it has to do with hydraulic pressure. My first guess is a sticky caliper. One mechanic told me the abs modules can go out (the one attached to the master cylinder) and cause a low pedal which would usually go away if you activate the abs and it pumps the pedal right back up to the top. I sure hope that's not what anybody here is experiencing because those units are pretty expensive.
 
#17 ·
when I make a sharp left/right/u-turn my abs activates and pulses which is really annoying. I'm not sure if my issue is caused by my tire just barely rubbing my body mount or maybe a sensor going out. My sharp turn issue is much different from your soft pedal though.
 
#21 ·
Has any one come to a resolution for this issue.
I have a had the soft pedal issue now for a year. No codes no dash light.
Once on a second pump I was almost put through the windshield.
I remember when it was a rock solid pedal.
296,000km's (183,925.87miles) on my 2007 FJ
 
#22 · (Edited)
Nos2fly and I had the same issues and the same resolution. Be sure to check and see if there is any play in the wheel bearing, make sure your brake caliper and hub bolts are tight. My issue was a bad wheel bearing Nos2Fly's issue was loose wheel hub bolts.

Here's a video of my bad wheel bearing

http://youtu.be/OLkACgUoWHA

https://youtu.be/CGQofS8iLzg

https://youtu.be/GZFzznNNibM

Keep us updated on your progress.

-B
 
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