Who says the calipers rust and freeze up? It's R-U-S-T ! 
Here in PA they put everything from salt to raw ashes that can cut your tires on the roads, so Yeah, these calipers RUST.
A few important Tips:
Rear brakes
1. Make sure the two halves of the caliper can move by hand. Yep, that means remove the brake line, pull them off. Drain the fluid out of the caliper first.
2. Put a can or something under the hanging brake line. It will continue to drip the entire time. Just be sure to top off your master cylinder when done. A little fluid drains and in effect flushes that line and does a partial change of your fluid.
3. Make sure the piston can push back into the caliper by very strong hands (fluid must be removed). Simply forcing it back into the caliper isn't enough, it must move freely and the dust boot must be in place
4. Remove the metal clips from where the brake pads insert into the notches on the caliper. Remove any rust or debris from this area (descale and/or file to remove rust), then replace clips. The clips should remain in shape and not be curled. If they curl, they have junk under them and will bind the brake pads.
5. Ensure the guide pins are free within the rubber bushings. These bushings will rust and eventually tear. They're about $6 a set. I like to put a little never-seize on the pins and inside the bushings. Hint, if the rubber bushings are twisting as you turn the pins to remove, they are likely compromises and are sticking to the pins- time to replace.
Front brakes
1. Those metal slider pins (about 1/8" diameter with the cotter pin) are one screwed up design! They rust between the halves of the caliper and refuse to be punched out. Scrape, file, whatever it takes to descale them and use a punch just slightly smaller than the pins to knock them through. I've used vise grips to grab the middle of the pin and spin it back and forth to loosen it up.
A grinder cleans up the pins nicely. I put a taper on the end, as it will mushroom as you punch it out. A little anti-seize on the pins helps a bit, but there's no good way to avoid punching them out.
Have new cotter pins ready, you'll need them. If the cotter pin breaks within the pin, be sure to file it down and don't leave even a minimal bump- else the pin will likely get stuck in the caliper when you try to punch it out.
2. Make sure the pistons push back in with reasonable force. I don't normally take these ones off. Just loosen the cap on your reservoir and loosen your bleeder.
3. Also make sure the clips don't have rust or debris under them, same as the rear.
4. Use a piece of wire to hang caliper from one of the coils over the shock to avoid putting stress on the brake line.
5. DON'T remove the bolts that separate the caliper itself! Remove the mounting bolts instead.
(Sorry, it's been a while since I did the front brakes, but I just did the rear and the info is fresh).
IMPORTANT: Make sure you refill your master cylinder before turning on your ignition key when finished with your brake job. The system pretty much takes care of most of the priming of the line electrically.
Don't forget to bleed the brakes. Don't be afraid to waste a little fluid here. Getting air out is important and it flushes your line.
Rotors
1. Remember to use brake cleaner to clean the new rotors before installing them. Don't get any on anything else. Brake fluid and brake cleaner are very bad for any finished surfaces (like paint!)
2. Chip away any corrosion between the center hub and the rotor and spray this area with PB Blaster or similar product.
3. Tap the "stepped" middle section of the rotor with a medium hammer all the way around (striking it towards the center hub). As an example, you will be striking litely straight down when tapping the top of this area. This frees up any debris and the parking brakes. Do this all the way around the rotor. You don't have to hit it hard, it's the vibration you're after.
4. If the rotor is really seized, you may have to put some Blaster around each of the studs to penetrate through the holes in the rotor.
5. Wiggle, tap, etc. You can also use the two threaded holes in the rotor to tighten properly sized bolts (I don't remember the size) just enough to put outward pressure on the rotor, then tap the rotor again as above. If you try to just drive the rotor off with only these bolts without tapping and working the rotor, you will likely strip your bolts and have a mess.
Wheels
1. Jack up vehicle, insert jack stands for safety, use a sledge on the inside of the TIRE ONLY. Strike the tire firmly, but not too hard to pop the wheel off the hub. (Yeah, Einstein, remove the lug nuts first! )
2. When putting the wheels back on, put the lug nuts on by hand first, wiggleing the wheel. These are concentric wheels and the lugnuts are designed to draw in and center the wheel. You just have to be sure not to bind the wheel during this process, hence the advice above.
3. Remove any "junk" stuck to the inside of the wheel, such as brake dust, mud, animal parts, etc
Wheels/Tires
1. Not exactly brake related, but these alloy wheels corrode like mad, too. When you are putting tires onto the wheels, be sure to clean up the sealing surface (bead area), as the flakes will cause slow air leaks.
2. If you haven't yet, replace the metal valve stem caps with plastic ones. Else they WILL corrode and MAY TWIST OFF the valve stem. It happened to me within the first year, leaving my TPMS useless as I had to use a regular valve stem, then removed my spare and the system won't function with only 4 sensors, regardless of dealer programming.
So these are some tips that I hope will make your 4Runner brake maintenance routine go smoother.
-DD
Here in PA they put everything from salt to raw ashes that can cut your tires on the roads, so Yeah, these calipers RUST.
A few important Tips:
Rear brakes
1. Make sure the two halves of the caliper can move by hand. Yep, that means remove the brake line, pull them off. Drain the fluid out of the caliper first.
2. Put a can or something under the hanging brake line. It will continue to drip the entire time. Just be sure to top off your master cylinder when done. A little fluid drains and in effect flushes that line and does a partial change of your fluid.
3. Make sure the piston can push back into the caliper by very strong hands (fluid must be removed). Simply forcing it back into the caliper isn't enough, it must move freely and the dust boot must be in place
4. Remove the metal clips from where the brake pads insert into the notches on the caliper. Remove any rust or debris from this area (descale and/or file to remove rust), then replace clips. The clips should remain in shape and not be curled. If they curl, they have junk under them and will bind the brake pads.
5. Ensure the guide pins are free within the rubber bushings. These bushings will rust and eventually tear. They're about $6 a set. I like to put a little never-seize on the pins and inside the bushings. Hint, if the rubber bushings are twisting as you turn the pins to remove, they are likely compromises and are sticking to the pins- time to replace.
Front brakes
1. Those metal slider pins (about 1/8" diameter with the cotter pin) are one screwed up design! They rust between the halves of the caliper and refuse to be punched out. Scrape, file, whatever it takes to descale them and use a punch just slightly smaller than the pins to knock them through. I've used vise grips to grab the middle of the pin and spin it back and forth to loosen it up.
A grinder cleans up the pins nicely. I put a taper on the end, as it will mushroom as you punch it out. A little anti-seize on the pins helps a bit, but there's no good way to avoid punching them out.
Have new cotter pins ready, you'll need them. If the cotter pin breaks within the pin, be sure to file it down and don't leave even a minimal bump- else the pin will likely get stuck in the caliper when you try to punch it out.
2. Make sure the pistons push back in with reasonable force. I don't normally take these ones off. Just loosen the cap on your reservoir and loosen your bleeder.
3. Also make sure the clips don't have rust or debris under them, same as the rear.
4. Use a piece of wire to hang caliper from one of the coils over the shock to avoid putting stress on the brake line.
5. DON'T remove the bolts that separate the caliper itself! Remove the mounting bolts instead.
(Sorry, it's been a while since I did the front brakes, but I just did the rear and the info is fresh).
IMPORTANT: Make sure you refill your master cylinder before turning on your ignition key when finished with your brake job. The system pretty much takes care of most of the priming of the line electrically.
Don't forget to bleed the brakes. Don't be afraid to waste a little fluid here. Getting air out is important and it flushes your line.
Rotors
1. Remember to use brake cleaner to clean the new rotors before installing them. Don't get any on anything else. Brake fluid and brake cleaner are very bad for any finished surfaces (like paint!)
2. Chip away any corrosion between the center hub and the rotor and spray this area with PB Blaster or similar product.
3. Tap the "stepped" middle section of the rotor with a medium hammer all the way around (striking it towards the center hub). As an example, you will be striking litely straight down when tapping the top of this area. This frees up any debris and the parking brakes. Do this all the way around the rotor. You don't have to hit it hard, it's the vibration you're after.
4. If the rotor is really seized, you may have to put some Blaster around each of the studs to penetrate through the holes in the rotor.
5. Wiggle, tap, etc. You can also use the two threaded holes in the rotor to tighten properly sized bolts (I don't remember the size) just enough to put outward pressure on the rotor, then tap the rotor again as above. If you try to just drive the rotor off with only these bolts without tapping and working the rotor, you will likely strip your bolts and have a mess.
Wheels
1. Jack up vehicle, insert jack stands for safety, use a sledge on the inside of the TIRE ONLY. Strike the tire firmly, but not too hard to pop the wheel off the hub. (Yeah, Einstein, remove the lug nuts first!
)2. When putting the wheels back on, put the lug nuts on by hand first, wiggleing the wheel. These are concentric wheels and the lugnuts are designed to draw in and center the wheel. You just have to be sure not to bind the wheel during this process, hence the advice above.
3. Remove any "junk" stuck to the inside of the wheel, such as brake dust, mud, animal parts, etc
Wheels/Tires
1. Not exactly brake related, but these alloy wheels corrode like mad, too. When you are putting tires onto the wheels, be sure to clean up the sealing surface (bead area), as the flakes will cause slow air leaks.
2. If you haven't yet, replace the metal valve stem caps with plastic ones. Else they WILL corrode and MAY TWIST OFF the valve stem. It happened to me within the first year, leaving my TPMS useless as I had to use a regular valve stem, then removed my spare and the system won't function with only 4 sensors, regardless of dealer programming.
So these are some tips that I hope will make your 4Runner brake maintenance routine go smoother.
-DD
