I *suspected* that one of the calipers was sticking on my explorer, because it was making a harmonic type sound (kinda like running your finger around a wet glass rim) and as soon as I touch the pedal, it goes away.
The rotors are new, as are the pads (carbon metallic).
I pulled the caliper off, and took it apart to see if it was corroded or anything, and found it to be pristine !.... the stainless pistons were perfect looking, as were the bores. and without the seals, the pistons slid freely in and out full travel.
So now I don't think it IS the caliper anymore. I put it all back together, and it's working for now, but I didin't really do anyting to fix it, so i am expecting it to return.
What year explorer? The ones prior to 95-96? had a different designed slider for the calipers. These were famous for needing frequent lubrication. If not lubricated the pads would freeze and mantain contact with the rotors and many a rotor was warped this way. This was one reason that the design was changed.
Whenever I perform a brake job, I always make sure that I clean the caliper surfaces with a wire brush (with the exception of the hose [rubber]). Next clean them with brake cleaner and allow the cleaner to evaporate. Finally after the pads have been loaded into the caliper, apply a light coat of anti-seize on all parts that slide back and forth (not the drift pins and NEVER the rotors or pads). Also remember to use the anti-seize sparingly as it gets EVERYWHERE. This will prevent the sticking or hanging caliper 99% of the time.
Additionally while you are at it, take a turkey baster (my wife freaked the first time she saw my TB in the garage, she didn't know that I had bought her a new one [it is a wonderful prank to play on your significant other =) ]) and remove all of the brake fluid from the master cylinder and empty it into a plastic container. Then open all of the bleeder screws on the system and allow the fresh new fluid to "gravity" bleed, this takes about 15 minutes or so, but you should have clean clear fluid by that time. Once you do close off the Right Rear side, then Left Rear, then Right Front and finally Left Front. Remember to add fluid as needed so that you do not have any air pockets in the system as you are bleeding the brakes. Also do NOT pressure bleed new systems (you remember, pump the brake then quickly open the bleeder, then close it once it hits the floor and repeat), like I used to do on old cars as it can damage the anti-lock sensors. One more note that is important, is that if you have a brake warning light on after bleeding the brakes the centering valve could be forced one way or the other. To correct this issue, open one bleeder screw and bleed the system a little a time until the light extinguishes. If it fails to, then try the opposite axle (front or rear).
If you were performing a rear brake job with drums you would also want to apply the cleaning sequence from the calipers above for the drums. I also recommend using a coolant drain pan to catch the brake cleaner after you completely hose down the drum hardware and shoes with brake cleaner. Remember if the hardware is wet than the brake dust is less likely to become airborne. You also may want to consider replacing brake springs completely as the price of kits has dropped significantly in the last few years. Oh yeah, only do one side at a time as well, that is a good rule of thumb even for the most seasoned mechanic.
I hope that I have mentioned something that will prove valuable to you.
Yes, these need to be lubed often with silicone dielectric compound. It is an easy job - remove the caliper slide pins, grease then and channels and put em back. I do mine yearly.
I assume you don't believe in the idea that the caliper seals pull the pads back slightly when the pressure is released? I am not sure I do, but I have seen the concept described in a shop manual.
Regards,
Ed White
Tim Tompk> Not to put too fine a point on all of this!
The pads on disk brakes are always in very slight contact with the rotors. There is no retraction mechanism as in a drum brake with springs to pull the shoes back when pressure in the wheel cylinder is released.
In reality the pads are pushed back by the small amount or run out that is always present as well as the heating due to friction of the pad to rotor contact. And there is usually a check valve in the master cylinder that keeps a very small amount of residule pressure in the hydraulic system. The result is a ever present beit slight pad to rotor contact.
Try this, measure the amount of torque required to rotate the rotor with the caliper and pads in place and then remove the caliper and measure the torque again. You will find that there is a difference due to the constant contact between pads and rotor.
In most applications the calipers 'float' and the slide/guide pins must allow free lateral movement. If the caliper does not move freely there will be squeel, chatter, excessive pad wear, warped rotors and probably a slight pull in the steering.
Interesting advice about draining the fluid like that.
As far as anti-seize compound, I think it's better to stick (pun alert?) with the dielectric compound. That's what Ford recommends, and I'm sure it could have recommended anti-seize if that were better. It is interesting that Ford engineers actually went through the effort to change the spec, from petroleum-based caliper lube to the di-electric stuff. So they thought about what is best to use.
Like you, I also wire brush the slide rails and the rear pad slots and clean everything really nicely. A coat of Rustoleum black keeps the outside of the calipers really nice looking, if that matters. I DO use a small bit of anti-seize on the back of the aluminum wheels, which prevents them from bonding to the surfaces, especially to the rear drums on my 92. The first time I took the wheels off, they bonding really made the job difficult. But I make sure I do not get ANY anti-seize on the studs, since that would have a force multiplying effect and skew the lug nut torque readings.
I should add that that dielectric compound, which seems gluey when you apply it, gets very slick and seems to have very good staying power. I really like it.
There may be a slight force to pull the pistons back from the seals, however I believe that is is so slight that it is insignificant in the whole scheme of things.
Once the brake pedal is released the check valve closes and leaves a very small pressure in the system that is probably more than the force from the piston seals.
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