Braking Pulsation

toyota
4runner

#1

I have had repeated instances of pulsation coming from my brake pedal during braking. Initially, the auto repair shop suggested a front brake job…which was needed to be done anyway (april 2009). A few months after the front brake job, the pulsation returned and they suggested that the rear axle seal had failed and axle fluid was now on my rear brakes causing the pulsation (Sept 2009). After having that replaced, this past weekend (Jan, 2010) the pulsation returned yet again. Upon returning to the shop, they suggested that my front calipers were sticking which had caused warped rotors. Me being not to happy with this, I brought the vehicle to another shop which discovered the rear seal was leaking again from improper installation, in addition telling me that my calipers were just fine (of which I have no symptoms of sticking calipers, overheating, pulling to one side during braking, etc). And that my warped rotor may have been caused by overcompensation due to my rear brakes failing.

So back to the original shop (MIDAS) I went to inform them of the under warranty repair they needed to make. But this time they told me that rear axle fluid on my rear brakes would not cause pulsation, which of course confused me. So the root of my question is, will rear axle fluid on my rear brakes cause pulsation? Or does it cause a chain of events leading to warped rotors?

I have conflicting opinions from a few shops and am wondering if anyone has any insight.


#2

Rear axle fluid (oil) will not cause the brakes to pulse, but they still need to fix the seal that is leaking.

Pulsing can be caused by warped rotors or a build up of residues from the pads. It seems to be getting more common lately, and most noticeable about a couple thousand miles after new pads are installed. First try making a couple of hard 60-5 decelerations. Don’t lock up the brakes, just hard braking, but don’t come to a complete stop. The heat from a hard deceleration will burn off the residues, if any.

If you come to a complete stop after hard braking, you will trap that heat on the part of the rotor under the pads, but the rest of the rotor will start to cool down, and that could lead to warping. If you don’t see a noticeable improvement after two of these decelerations, then the rotors are probably warped.

Warping could be caused by some braking technique you are using, cheap rotors, lug nuts improperly torqued or something else, but I really doubt that it is technique, it happens to a lot of people.