Hi. I have the 13WL upgrade, calipers originally sourced from Napa. I've had the setup for about six years now. I've always used Centric Blank rotors and OEM pads.

I've noticed for a long time now when I press the brakes, especially at lower speeds coming to a stop, and pressing somewhat hard, that the 4Runner will consistently pull to the passenger/right. It's been doing this for a long time now. I just did a brake job a couple of months ago hoping that would go away, but it did not. I again did new OEM pads and Centric blank rotors. Still getting the same pull to the right.

Long story short, coming down a mountain pass (after the recent brake job) my brakes got HOT (learned quickly that you have to ride your gears when traveling through Colorado). Anyways, I noticed both sides were extremely hot and both the rotors had turned purple passenger/driver, however the right/passenger side was noticeably hotter than the driver side.

Given all of this, I'm pretty certain my front passenger side caliper is producing more force than the drive side, for whatever reason.

I'm not even sure where to begin diagnosing this. Is it the caliper itself? Is it the actual brake line pressure on the passenger side that's causing the uneven pressure? Is this just a common symptom of a bad/seized caliper (and if so, is it the driver or passenger that's bad?)? Or is this just how every 3rd gen 4Runner behaves?

Pic for attention...

I’d start with a brake bleed if your brake hoses are not cracked.


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I'd replace the front brake hoses and rebleed, but typically a pull when braking is worn control arm bushings so check those as well. Have someone drive straight while you watch each front wheel for a change in toe when they brake to see if it's a control arm bushing issue.

When my bushing went south I could feel play with my finger as my wife wagged the steering wheel.


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I’ll also say that between replacing the hoses (were beyond shot) and the LCA bushings my slow sharp right hand turn with foot on the brake activating the ABS is gone.


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I appreciate all of the help! Apologies, I forgot to mention that I did a full flush and bleed after replacing pads and rotors.

The lines are not cracked and there's no sign of leakage I can detect on the calipers. Running SS braided lines, installed maybe 50k miles ago by Sonoran Steel when they installed my lift at the time. It might be worth replacing just to be safe as they've got a few years and miles on them now.

This occurs when braking straight so I don't think it's a symptom of ABS activating when turning.

I'll check for play in the bushings. When I did the lift (again, maybe 50k miles ago), I also installed new OEM lower controller arms at that time. So the bushings should be good on lowers, but the uppers are original and likely needs replacing regardless.

^ Question on the above, if it were a bushing/joint, would the passenger side brakes also get noticeably hotter than driver side like I observed? Not sure how uneven toe during braking would cause the uneven heat as well.

Am I overthinking this and it could just be a seized caliper?

It could be your left front caliper has a seized piston and causing an uneven braking force. Do you have an infrared thermometer to compare the temps of each side?

Any chance the alignment is not right? Mismatched L/R alignment (mostly camber) can do that too. That would be assuming that the difference in heat you felt Left to Right was imagined, not real (sunny on one side, you were looking for a difference in temp, etc.).

-Charlie

Ah, so driver-side isn't producing as much force, making it seem like the passenger side produces more force. Interesting!

I do, yes. However, when I heated the brakes coming down a mountain, the passenger side was noticeably hotter to the touch (at the hub). I can retest, just need to heat up the brakes real good again I'm thinking.

This issue persisted between alignments. I had it aligned right before I went on a trip to Colorado in June. The pull was the same before and after alignment, and remains consistent after 2k miles of road tripping since last aligned.

Yes, that is possible that I was biased in thinking the passenger side was hotter, and in reality it was some other variable like that sun. I touched the hub, and am fairly certain I noticed the difference because passenger side was too hot to hold on, but drivers side wasn't quite as bad (but again very hot). But looking back I was coming through some twisties so I don't think the sun had a chance to bake one side more than the other for too long. You could be onto something though.

I'll see about going for a drive again and testing temps when I can.

How are you bleeding the brakes?

Please don’t tell me you’re pumping them to make pressure and then opening the bleeder………all that does is takes a few big air pockets and turns them into a million micro-bubbles that migrate everywhere.

I always start with a good gravity bleed using synthetic DOT 3 or 4 fluid then I do the below with a helper. If no helper I have a long board I use to hold the brake against the floor while I operate the bleeder.

You….open bleeder-depress brake pedal to the floor-close bleeder-take foot off brake pedal.


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Those are great instructions. I believe I do properly bleed them. Fortunately/unfortunately the race car requires bleeding before every race weekend (and sometimes at the track), so it's something I've gotten a lot of experience with. That said, the pull was consistent before and after the flush so I don't think that's causing the issue since it's persisted, but I'll take a look and do a quick bleed just in case to be thorough.

If you flush and bleed alone, Motive makes a really nice manual power bleeder that has come in handy for me many times. Does a better and quicker job than gravity bleeding I've found, but it does waste some fluid in the process I've noticed.

Hopefully I'll find some time this weekend to diagnose this a bit more. My money is on a bad caliper (hopefully that's it because they are NAPA lifetime covered), but we'll see. I'll check bushings, joints, and anything else while I'm under there and report back.

I have the pressure bleeder also.

Edit: I left fluid in the pressure bleeder and it sat a while and when I went to use it earlier this year the hose was cracked. It’s a simple fix it’s just that using that universal cap is a pain and I can’t put more than 5psi on the tank before I get leaks


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TLDR: driver-side caliper was seized, new calipers fixed the issue


Closing the loop here. The problem was that the driver-side caliper was seized. The driver-side produced less braking force compared to the passenger-side, causing the uneven pull to passenger side when braking.

I debated between taking my Napas back for the lifetime warranty, but decided to try out the PowerStop remanufactured instead. Anyways, the issue is gone and when I brake the 4Runner brakes straight with no more pull to passenger side. Fixed!





Thank you very much for all of your help and suggestions!

You could rebuild that bad caliper if you kept it. Speedy's Garage has a good video on the subject.

Hopefully your rotors survived the purple. Sounds like they did. I had this happen once in my Cherokee and the rotor got warped. If you got to keep the caliper like the other man said it's simple to rebuild. Enjoy the sweet rig 🙏