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light brake pedal pulse

16K views 47 replies 9 participants last post by  istambull 
#1 · (Edited)
I've been chasing down some strange feedback at the brake pedal for a few weeks. All started after returning from a trip to Colorado, it rained epic amounts on the way there and back but they symptoms only surfaced after I made it home. Feels is very similar to ABS or when ATRAC activates but not nearly as aggressive. It mostly occurs with light breaking at 20 MPH or lower but can not be produced consistently. My first thought was a rotor with some run-out so I swapped all of the brake wear components, sadly no change. The speedometer also has occasional irregular behavior mostly above 60 MPH where the needle jumps around +/- 3 MPH. When this occurs cruise control is still available but no fun to use.

Dash Lights - None of the typical trio lights are lit up. No ABS or a check engine either.

Codes - Had the truck scanned at O'Reilly's a couple times and it showed faults with both rear wheel speed sensors. All have been cleared with the reader but I suspect they will be back.

Parts Changed
4 new rotors
4 new pads
4 brake sensors not new but from a working vehicle. Thanks @RichJacot

Service - Cleaned sensors at all 4 corners and removed the grease from their mounting holes. Disconnected, cleaned and inspected wheel speed connectors and where the 2 rear meets the harness above the passenger spring. All were cleaned with QD contact cleaner spray. No breaks or obvious damage to the wires or connectors. Cleaned/Polished the plunger assembly in the brake accumulator.

Here is what we have done to "fix" it and where it gets weird.
***incorrect***Unplugged the black connector at the hydraulic brake booster and all symptoms are gone but at the cost of no ATRAC (possibly more) and the brake indicator light is on. I believe this is the Skid Control Unit that is integrated? into the brake booster.


Has anyone seen this and know a solution? If it turns out to be the brake booster how difficult is the swap?

Thanks,
J
 

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#3 ·
This may sound crazy at first read but I have experienced it first hand. A wheel bearing starting to go out will start to shed very fine metal "dust". That metal will work its way into the wheel sensor area and cause false readings. Obviously that may not be your problem but it is a place to checkout. You won't be able to simply pull the sensor and wipe off and say your done. Pull the wheel and inspect the wheel bearing with your eyes and feel it by spinning with your fingers.


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#4 ·
Funny you should say that, I have two front bearings due for delivery today. One side has obvious play the other will get swapped regardless. There is no noticeable play at the rear on either side, fingers crossed the front is the culprit despite the codes pointing to the rear.
 
#5 ·
I understand your codes pointed to the rears. Still a factor tor consider. I simply don’t trust the primitive code structure with the FJ so I also factor that in. I won’t rule something out just because of what codes may or may not show up.


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#8 · (Edited)
Significant improvement after last night's swap but still not 100%. At least I'm back to having all electrical components connected. Hope to change the other in a couple days then if need be I'll move to the rear.

Anyone know how long the codes remain after clearing them? Zapped them on Sunday but have only logged about 30 miles since then.
 

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#11 ·
Perhaps a sticking caliper? I had this happened on the fronts of my '07 FJ. It started as a mild pulsation when applying the brakes at freeway speeds. About 1,000 miles later, I dynamited the brakes and it vibrated violently, with a hard pull to the right. Took it to the shop and new calipers, rotors, pads and a $1,000 later all was good....
 
#12 · (Edited)
I have had two issues with funny handling. The steering on mine started to wander on gravel roads when going around turns. I could feel some tugging in the steering that should not have been there. It seemed to me like it was getting some bad help from the traction control system. I had it aligned and the problem went away. The wheel alignment was a little out but basically ok. The VSC Calibration (Vehicle Stability Control) was 30degrees off. I believe resetting the VSC was what solved problem.

Second issue: The anti-lock brake system would kick in at some funny times. Dry, good pavement not even a panic stop. Lots of pulsing through the pedal and double the stopping distance. It prompted some shoulder driving. It had done this a few times since new. I was able to get it to happen with two quick stabs at the brake. The dealer said "they are supposed do that". I changed out the brake fluid at 70thou and found the left rear wheel had a whole lot of air in it. I mean a whole lot of air. That was the first time the brakes had been touched. I have tried to get the antilock to kick in a couple of times since then (pavement, dirt roads) and have not been able to replicate the issue. I read you have changed everything out but you should do your own bleed just to take the issue off the table.

I hope this helps.
 
#13 · (Edited)
Back from the dead. Sorry for the delay guys, had surgery and the holidays... The vibration problem is still present and my initial "fix" was incorrect. Since my original post I've noticed that even with the black plug disconnected the pulse is there. I have moved on to disconnecting the smaller gray plug that some manipulate for the TC hack and the black plug is connected again. This deactivates traction control, VSC OFF and VCS TRAC. You will get 3 yellow dash lights and the brake light will be on but with this you can at least drive without fighting traction control and ATRAC is functional should you need it. Still eager to find the source but I very much like the sound of a fluid flush and bleed being a possible fix, needed to do this anyway as its been 4-5 years.
 
#14 ·
@istambull. I hope you are feeling better and recover fast brother. It maybe worth looking into this as well, I say do this first before you flush the system.
https://youtu.be/5eR4bwgbSZs


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#16 ·
I'd go back to your very first assessment (front rotor runout) and VERIFY, by measurement, that the runout of BOTH faces of BOTH front rotors is less than Toyota's spec of 0.002" maximum. This is actually a very tight runout spec, and even though you replaced both rotors I will assume that you did not actually measure runout with the new rotors in place. Obviously, the target is zero runout.

Mount a .001" resolution dial indicator on a magnetic base, attach the base to the spindle, and measure runout ~ 15mm in from rotor's OD. Toyota's recommendation for dealing with rotor runout is:

1. Make sure that the mating surfaces of rotor and hub are surgically clean. Carefully wire-brush all mating surfaces to remove any traces of corrosion; you may need to use a gasket-scraper to make sure the surfaces are dead flat and clean.

2. If the runout is small (slightly over .002"), re-index the rotor on the hub and re-measure. The hub will always have some small runout value due to machining tolerances, as will the rotor. Depending on how the parts are "clocked", in some cases the runout of both parts is additive, and in some cases you can clock the parts so the runout tends to cancel. You have six different possible orientations to evaluate via assembly and runout measurement.

3. If steps 1 and 2 don't yield a good runout value, then measure the runout of the hub. If the hub runout is good, then you likely have a defective rotor, even if it is brand new.
 
#18 ·
If you don't gag too much buying Chinese tools, the Harbor Freight 63656 looks like it should work, although I haven't actually tried it. It has a modified "Vise Grip" type base that clamps onto your spindle or other attachment point near the rotor, a conformable/lockable indicator support arm, and the dial indicator itself for <$35.

There are many other "articulated-arm" type dial indicator supports with clamp-on or magnetic bases that are US, Swiss, or German made if you don't mind shopping on eBay.

One thing I forgot to mention is that lug nut torque and torquing sequence can also be critical in minimizing brake pulsation. It is highly recommended that you use a torque wrench to get the nuts uniformly torqued in at least two stages.

After making sure that all mating surfaces on wheel and hub are surgically clean, install the wheel, taking particular care with aluminum wheels not to scrape the wheel against the studs and create aluminum filings that might get trapped between the wheel and the hub.

Then, tighten all lug nuts "hand tight" only, installing them in an alternating pattern on opposing studs.

Next, tighten the nuts to ~50 ft-lbs, again using the alternating-opposing pattern.

Finally, lower the jack so the tire just touches the ground, but does not bear the full vehicle weight, and tighten the nuts to 75 ft-lbs, again using the alternating opposing pattern.

I always go back a few days later and re-check torque on all nuts, tire-on-ground, using the torque wrench set at 75 ft-lbs.
 

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#21 ·
I remember another issue.
Since you have the Currie rear axle, it is worth looking into the rear “HUBS”.
When Currie machined the rear hubs they failed to mashie the outter center hubs in 2 stages.

The first stage which the wheel is going to seat is 106MM the second stage is 108MM which will “CENTER” the Rotor on the hub and will seat flush against the wall of the hub.

The Currie axle shafts and hubs are one unit just like the OE hubs, but they have machined the entire outer lip to 106MM.

The only way this can be fixed is to get an 106mm to 108mm centric wheel adapter.

This has happened to one of my wheeling friends since he has the exact same Dana 60 like yours. I am 99% sure your hub is machined to 106mm.

Measure the “vertical run out” and I am positive it will be huge.
Hope this is what causing the pulsation in the brake pedal.

I have called my friend and he will bring his truck tomorrow morning and will take the wheel oof and take some photos and will post it.

OEM HUB.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/283102446931


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#24 ·
I remember another issue.
Since you have the Currie rear axle, it is worth looking into the rear “HUBS”.
When Currie machined the rear hubs they failed to mashie the outter center hubs in 2 stages.

The first stage which the wheel is going to seat is 106MM the second stage is 108MM which will “CENTER” the Rotor on the hub and will seat flush against the wall of the hub.

The Currie axle shafts and hubs are one unit just like the OE hubs, but they have machined the entire outer lip to 106MM.

The only way this can be fixed is to get an 106mm to 108mm centric wheel adapter.

This has happened to one of my wheeling friends since he has the exact same Dana 60 like yours. I am 99% sure your hub is machined to 106mm.

Measure the “vertical run out” and I am positive it will be huge.
Hope this is what causing the pulsation in the brake pedal.

I have called my friend and he will bring his truck tomorrow morning and will take the wheel oof and take some photos and will post it.

OEM HUB.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/283102446931

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There may be some confusion here on the difference between "radial runout" and "axial runout", and which type of runout creates brake pedal pulsation vs tire balance problems.

The 106mm/108mm locating diameter you mentioned is intended to center the rotor and the wheel on the hub. If the rotor (or wheel) is not centered (not coaxial), the rotor or wheel will have runout at the outer diameter (radial runout), but will run true (no wobble or axial runout).

Slight radial runout of the rotor will not cause brake pedal pulsation, but it can cause a tire imbalance problem since the entire mass of the wheel + the tire will not be turning coaxially with the hub/wheel bearings.

Axial runout caused by a warped or mis-machined rotor, bent or mis-machined hub, or debris between the hub and the rotor will cause axial runout that will inevitably cause brake pedal pulsation.

There is also a theory that non-uniform deposits of brake pad friction material deposited on the face of the rotor can also cause brake "grabbiness" that can feel like pedal pulsation, even though the rotor is running true.
 
#23 · (Edited)
And I didn't intend to come across as promoting HF tools, just that for a once-or-twice a year "home mechanic" use, the HF tool will probably do the job, and is very inexpensive (bearing in mind that you get what you pay for).

It really discouraging to see how many long-established US name brands, who earned their reputation for quality with their US-made products, are now sourcing some (or many) of their products in China. Even Starrett is now selling Chinese-made tools under the Starrett brand.

For an interesting read, check out "Poorly Made in China", a book by Paul Midler. Touted as "An Insider's Account of the Tactics Behind China's Production Game", it accurately reflects my own experiences in dealing with vendors in China and Taiwan.

Business ethics and codes-of-conduct that are SOP in dealing with vendors in the rest of the world are essentially non-existent in China; "signed contracts" in many cases have no real meaning and are non-enforceable. Quality and pricing may initially be acceptable, but as soon as you are "locked-in" to a specific vendor, quality may decline, prices may suddenly increase due to "unforeseen circumstances", and if you don't accept the crappy quality or price increase, there may be "unforeseen delays" in receiving products that you have already been paid for.

Personally, I do everything I can to avoid purchasing anything made in these countries, unless there is absolutely no other option. Unfortunately, with the decline is US manufacturing, many times there just are no options.

(End of rant ...)
 
#25 ·
Appreciate all the input here guys. I'm in no shape to turn wrenches and pull a tire at the moment but am willing to get the spacers in transit for when I am. At $20 its worth a shot. Usually go overboard with cleaning anything that comes off the truck. If it isn't spotless I always clean it before reinstall.
 
#26 · (Edited)
Crap photo is crap but according to my eyes my Currie hubs were not machined with the step down to 106 mm. Nothing but the typical Currie rust. Having said that I have not pulled the wheel and measured just yet. Gonna try to have a friend over this weekend to help with the heavy lifting. Thanks in advance @RichJacot When compared to the front which has with Spidertrax spacers installed the gap around the hub centric ring is comparable to the rear. I did ditch the Method center caps which kinds serve as a spacer but those have been gone for well over a year, maybe two, and the problem only began in Oct.



What's left of the Method caps


How I have em now.
 
#30 ·
Sorry guys I'm confused. Are the 106 mm to 108 mm rings intended to center the rotor on the hub or the wheel to the hub? There seems to be a few Toyota threads where these were used to clean up wheel shimmy and I assume they installed them on the wheels.
 
#31 ·
The 106mm will center the wheel and the 108mm will center the rotors.
You can compare your rear hubs to the front. You will see your front hubs are machined in 2 stages, and when installing the rotors, on the front or rear they should have no “PLAY” on the hubs what so ever, it needs to be nice and snug.

“Edit “

You may have the same symptoms like my friend had some 2 1/2 years go, with his Currie axle and this is a simple fix.

I hope this will solve your issues with the break panel.


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#32 · (Edited)
Okay clearly I am struggling with the machined step on OEM or Currie axles but we wade some progress! Thanks @RichJacot . Only problem is I'm not exactly sure what we did that helped. For now I'm back to having the ABS plugged in, no brake pulse and the wheels are rolling smoother than they have in months.

Today's session:
Cleaned hub and brake surfaces where they touch and around the circumference.

Checked runout with harbor freight dial gauge. One side was .003, technically out but just barely, and the other about .018, very out. Had the worse of the two turned but didn't see any improvement on the dial gauge once back at home. Clocked the rotor 180, also no improvement on the dial.

Cleaned and lubed the guide pins.

Installed the 106 - 108 aluminum rings from China. I DO NOT have the machined step down in the Currie hubs seen above. My rotors are tight on the hubs and measure 106, no play here. The only place I could see these being installed and providing any improvement was over the hub after the rotor was on. The Method wheels were machined to allow use of a center cap which got pitched months ago. I guess the new al rings help me center wheel to the hub similar to what the Method caps were doing? IDK for certain here since I ran without the caps for nearly a year before any problems surfaced.













 
#42 ·
Okay clearly I am struggling with the machined step on OEM or Currie axles but we wade some progress! Thanks @RichJacot . Only problem is I'm not exactly sure what we did that helped. For now I'm back to having the ABS plugged in, no brake pulse and the wheels are rolling smoother than they have in months.

Today's session:
Cleaned hub and brake surfaces where they touch and around the circumference.

Checked runout with harbor freight dial gauge. One side was .003, technically out but just barely, and the other about .018, very out. Had the worse of the two turned but didn't see any improvement on the dial gauge once back at home. Clocked the rotor 180, also no improvement on the dial.














Sounds like you only turned one side of the rotor?
 
#34 ·
How many miles on the rear axle?


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#37 ·
Pic test #1

Currie axle hubs and the brake rotor bores measured right at 106 mm, no play here.

Aluminum 106 mm to 108 mm spacer from China.

Spacer fits nicely in the center bore of the Method 105 without the center cap.

Snug fit but was able to install the rings without any troubles.
 

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#44 ·
You replaced the rotor right after you noticed the pulsing (from what I read on page 1)? With what brand and did you bed the pads? I'm inclined to say that runout is enough to make some odd vibes and when the run out is not significant enough to cut the rotors even, you'll still get pulsing. Happened to my dad's lexus and it was my fault that I didn't bed the pads in (even if the directions state to slowly bed them over xxx miles). Someone else in household drove my dad's lexus for an evening and the next day it had pulsing on hard braking. I believe that bed-in procedure is outdated and when you transfer any pad material within that time, you might experience the funny pedal feel. Not saying it's the fix but you may need to replace rotors again if all other drive train components are behaving correctly (bearings/hub/axles).
 
#46 ·
StopTech

....Not saying the old equipment wasn't toast but man I'm really lost here.
Good stuff. Doubt it's the hardware you replaced then but still questioning... You bought that rearend used from another member? I've heard of drive train vibes but not necessarily pulsing on braking which seems strange to me. Usually the vibration would be on acceleration.

If you haven't already, I would get a second opinion at a mechanic's shop. Instead of replacing everything, maybe a test drive by a professional can tell you what you should and shouldn't be looking at. Besides, most will test drive for free :thinkerg:
 
#47 · (Edited)
Not opposed to having the other rotor turned or getting another set of eyes on this. The new brakes were bedded according to StopTechs recommendations, apply force just prior to activating ABS and don't come to a complete stop or activate the e brake while hot. I'd even replace pads/rotors on one or both sides if I knew definitively that would solve the problem. I think what bothers me most is not knowing and if I swap bearings, brake parts and fluid all at once I may never know and that will drive me nuts. Guess I'll start with clearing the coded another time and double checking my work with the bearings are in transit.
 
#48 · (Edited)
Finally decided to pick this back up and surprisingly made some progress. Drove the FJ for the first time in 3 + months without wanting to drive it into a ditch.

Ran about a liter of new dot 3 fluid through and saw great improvement. Did my best to exercise the ABS pump on the road. Is there an easier way for us at home to get new fluid through the ABS components or is the activation at start up sufficient?
 
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