I have had this problem for a few months. While driving, when I mash the brakes I can feel the steering wheel pull to the left and right as I slow down I can tell that the problem is in the braking system. I noticed that the right front beake pads weren't wearing evenly. I thought that it might be a warped rotor so I replaced it. It worked fine for a few days but it came back. I thought it might be another warped rotor, but it's hard for me to believe that.
I know that other 4Runner owners have had this problem, so could you tell me what did you do?
Do you think it's the caliper?
Opinions welcome
Are the pads wearing uneven from top to bottom or uneven from the outside pad as compared to the inside pad? On my 03 I had to replace both calipers as the lower piston on both inboard sides had frozen up and could not compress them for pad replacement.
It is a fixed caliper with 2 pistons on each side. The outside pad is wearing more than the inside. It's uniform from top to bottom. I replaced them about 2 months ago because of this problem. I put new pads on and bought a new rotor thinking ithat the old one was warped. It was fine for a few days but the problem came back. I took the wheel off yestorday and found the samething, the outside is wearing more than the inside again. It's not that bad yet but I have to do something soon.
Other people have posted this problem and were told what to do but I have not seen any follow-ups to whether it solved their problem or not. I greased the slides but that didn't solve my problem. When I replaced the pads I didn't have a problem pushing the pistons back into the caliper.
Just thinking here, could the inside pistons have more resistance on them than the outside? What would cause this? It's hard to believe that the problem is in the brake fluid because you would think it would be happening to the other wheels.
What I would do to troubleshoot the problem is remove the caliper from the mount and put a piece of wood between the pistons and depress the brakes and see if the pistons can move out at the same distance on each side. Caution make sure the piece of wood is thick enough as to not let the pistons come out all that way and make a big mess. But you do want to go out far enough to make sure they are smooth and all is well. On the suspect pistons you want to make sure they do not hang up going out, and are smooth when compressing them.
Thanks Jetwhine,
Sounds like a plan. I will try that this weekend. I'll get a friend of mine to mash the brakes while I watch to see if the pistons move freely. I might try removing the pad on the inside first and hopefully I can put the lug nuts back on to support the rotor if not i will try to support it some how, maybe washers. I'm thinking if I put some resistance on the outside pad the inside should move freely and vice versa. I'll let you all know what I find.
You don't have to worry about holding it nothing will happen to you if you keep your fingers out of harms way. I would use the wood as you can watch it closer that way. Don't mash too hard as this makes it hard to get the pistons out of the wood.
All four cylinders/pistons in the caliper move therefore they are not seized. I noticed when we mashed the brake the lower one extended first and once it contacted the wood the top one extended. This is true for both sides. Knowing a lot about hydraulics I can understand that.
From what I saw and what I know I feel that there is nothing wrong with the caliper except that I think it's a bad design. Two cylinders pushing one pad. Sounds good but bad design. The pressures inside of them have to be fluctuating back and forth as soon as you mash the brakes.
I will have to analyze the situation a little longer before I figure out my next move.
Hey Jetwhine,
Didn’t have to worry cylinders moved so slow I could have put my fingers in between there with no problem LOL. I don’t know what kind of pressure it takes to move those little cylinders, but I am sure it isn’t much. The pressures that I deal with at work are like 5000psi. and the cylinders are capable of producing 800,000 thousand pounds of load in the matter of seconds. So every part of you better be clear, if you know what I mean.LOL
I know too well what high hydraulic pressure can do. As far as I am concerned if they are not wearing uneven from top to bottom then I would say they are ok and not worry about it.
OK,
Here is a follow-up, took the rotor off the right side had it turned, cleaned the pads and caliper then reinstalled. Better but still not good. Did the samething to the left front side, problem solved.
Rotor on left front did seem to be a little uneven ( high spots). Pads and caliper were good. Cost $32.84
Good another happy 4runner owner.
I replaced my rotors at 100,000 mi. and have not had any issues.
Usually when you do a pad job you should have the rotors turned as they will be true with the new pads. Just something I do when replacing the pads and saves trouble later when pads start to wear.
not sure anyone mentioned pads. what are you using? Always go with toyota pads. You can turn or replace rotors all day long but the problems will eventually come back with a crappy pad.
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