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1G How to rebuild rear brake calipers

Posted by Calan, Feb 21, 2010

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  1. Calan

    Calan DSM Wiseman

    6,015
    274
    Joined Jan 16, 2007
    OKC, Oklahoma
    This article will describe how to rebuild the rear brake calipers on a 1G DSM. Much of the information also applies to the front calipers, but there are some major differences. You may want to read my article on How to rebuild front brake calipers before tackling the rears.

    As I've stated before:

    DISCLAIMER: Screwing around with your brake system is not something to be taken lightly. If you don't feel that you are 100% capable of taking on a project like a caliper rebuild and doing it correctly, leave it to a professional. Duh.

    Note: This article assumes the calipers are on the bench and ready to be rebuilt. Refer to the factory service manual for instructions on removing them from the car. Also, this is based on the rear calipers from a '92 Talon TSI, but other models will be similar.

    caliper_1.jpg

    What You'll Need

    • rear caliper seal kit (for '92 TSI AWD - O'Reilly's #15228 )
    • a dull flat blade screwdriver
    • a 1/4" strong spring hose clamp
    • some type of bushing approx 9/16" OD x 3/8" ID. (more on this later)
    • circlip ("c" clip) pliers
    • special tool for removing the piston, or medium-sized vice grips.
    • needle nose pliers
    • a source for compressed air
    • rags
    • brake cleaner or Simple Green, etc.
    • high-temp lithium grease or equivalent
    • 1500 or 2000 grit sandpaper or emery cloth
    • DOT3 brake fluid
    • a dental pick or something similar
    • latex gloves (unless you like that warm fuzzy feeling of brake fluid under your nails)
    • factory service manual (highly recommended as always)

    Note: I used the O'Reilly's kit because it is only about $3 a side, and appears to be the same quality as OEM or NAPA kits that I've used in the past. It doesn't come with new pin boots, but mine were in good shape and could be re-used.

    FSM_1.jpg
    FSM_2.jpg

    Disassembly

    The biggest difference between the front and rear brake calipers on a 1G is that the rears include a mechanism for the emergency brake that is integrated with the piston. Because of this, there are some major differences in how the calipers are disassembled and rebuilt. I will say up front that removing and reinstalling the emergency brake mechanism inside the caliper can be a total PITA, unless you use the right approach and have some patience.

    Once the caliper is off the car and the bracket and pads are removed, the first step is to get the piston out of the bore. Unlike the fronts, the rear caliper piston screws in and out of the bore rather than just pressing in. The manual recommends a special tool to do this, but if you are careful not to scratch the piston you can use some pliers to carefully thread the piston out of the bore. A better way is to cut notches into a piece of 1 inch dia pipe that fits the top of the piston...either way will work though.

    The FSM states to remove the boot and then the piston, but I find it much easier to remove the piston first and then the boot. After threading the piston out a few turns, slip the boot down out of the piston groove and then thread the piston all the way out. Be prepared for fluid to drain out of the caliper once the piston comes past the seal. Once the piston is out, remove the boot and then pry the boot ring out with a flat blade screwdriver, being careful not to scratch the bore. You can also go ahead and remove the piston seal at this point, but it will be easier if you wait until everything else is out of the way.

    remove_piston.JPG

    Next, remove the guide pin boot, lock pin sleeve, and lock pin boot if you haven't already. Slide the lock pin sleeve out, and then carefully work the boot free from the caliper. Once it's unstuck, you can fold it in half and work it out of the caliper.

    And now for the fun part (or not)...

    Removing the auto-adjuster spindle assembly can be either relatively easy, or mind-numbingly frustrating. The FSM states to use a piece of 3/4" pipe to press down on the spring, and then remove the c-clip. Apparently whoever wrote this has a great sense of humor. Unless you have very skinny circlip pliers with long tips, there is no way you are going to get them down between a piece of pipe and the cylinder wall... much less actually get it into the clip to compress and remove it. After modifying my pliers and trying every piece of pipe and socket that I could get my hands on (and about 2 hours of inventing new derogatory words), I came up with a much better method.

    Note: To be perfectly honest, I did eventually manage to wrestle the clip out by depressing the spring case with a small socket and somehow getting lucky with my modified pliers. But it was incredibly difficult, and putting it back together was completely impossible with this method.

    What I came up with was to slide a bushing over the auto adjuster spindle and into the spring case (which keeps everything centered), and I then put a small spring hose clamp over the spindle to hold the bushing in place. This keeps the return spring compressed and still allows room for the pliers to grab and compress the clip. The bushing needs to be slightly less than 9/16" OD to slip inside the spring case, with a 3/8" ID to slip over the spindle.

    I used a flare fitting that I drilled out to 3/8", and it works perfectly. For the clamp I used a stock vacuum hose clamp. Just be sure the clamp is stout enough to hold the bushing down. Here is the flare fitting I drilled out and the clamp I used:

    clamp_and_bushing.JPG

    The following image shows how the bushing and clamp sit on the adjuster spindle, and how the pliers were then positioned to remove the clip (The clip was already removed when I remembered to shoot the pic).

    remove_c-clip.JPG

    With the c-clip removed, you can lift out the spring case, spring, stopper plate, and spindle. There is also a little bullet-shaped connecting link that sits at the bottom of the spindle. It just floats loose and is held in place by grease, so it may or may not come out with the spindle. If not, just use a screwdriver or some skinny needle-nose pliers to carefully get it out. Also note the o-ring around the bottom of the adjuster spindle.

    Note: The FSM shows both a stopper and stopper plate at the bottom of the spindle, but my calipers had just a single piece here.

    Once the auto adjuster spindle assembly is out, remove the large brake lever return spring. If you want to separate the parking brake lever from the spindle lever for cleaning, it is much easier to break the nut loose while the spindle is still in the caliper. Remove the nut and lock washer, and then pull the lever and spindle out of the caliper together. The brake lever will probably be stuck onto the spindle, but can be knocked loose with a few taps from a mallet or hammer. (Be careful not to scratch up the spindle getting it off). The easiest way to do it is to screw the nut back onto the spindle threads, insert the spindle into a large deep-well socket, and then tap the nut with a hammer until the spindle pops out of the lever.

    Note: Some WD-40 will help here, since the nut will probably be rusted onto the spindle.

    Here is the caliper with all the parts removed. You can see the bushing I made and the small clamp circled in red at the lower right. Also notice the brake lever, still pressed onto the lever spindle at this point.

    disassembled.jpg

    Once the brake lever and spindle are out, you'll notice a rubber boot and a needle bearing inside the rear of the piston bore that the brake lever spindle rides in. The FSM shows the boot to be removable, but on my calipers it is actually pressed in and bonded to the caliper and can not be removed. Fortunately the boots and needle bearings were in good shape on both calipers, although nasty and full of crud. My guess is that if either of these are damaged, you'll be looking for a new caliper.

    You can see the needle bearings in the image below, after everything has been cleaned up. Also notice the small rubber "stopper" that came out of the end of the guide pin housing. I removed this so I could clean the inside better, but it can be a PITA to reinstall without tearing a hole in it.

    needle_bearings.jpg

    The last step is to remove the piston seal if you haven't already. The easiest way to do this is to use an exacto knife, razor blade, or sharp dental pick to carefully stab the seal and work it out of the groove enough to grab hold of. You can also remove the parking brake cable bracket from the caliper if you wish.

    Cleaning

    With everything apart, clean the inside of the cylinder bore and piston as much as possible with some brake cleaner or something similar, and check for any deep pitting or scratches. If the piston has some slight surface rust, you can lightly wet-sand it with some 1500 or 2000 grit sandpaper. Just don't over do it or scratch the piston.

    Use a wire brush in a hand drill or drill press to remove all the rust and grease from the outside of the caliper, and then go over it with some Simple Green and a stiff brush. Be sure to clean the brake line and bleeder ports, and remove all the old grease and dirt from the needle bearing and the bottom areas of the bore. (I sprayed the needle bearings with cleaner several times and used my pinky to spin them around and work the cleaner in). Be sure to get down around the bottom of the bore really well. Rinse everything off and use some compressed air to help dry it out as quickly as possible to keep rust from forming before you get it back together.

    To clean all the internal parts, I used some Simple Green and hot water in a small bowl. After thoroughly cleaning the parts, I dried them with some compressed air to prevent any rust from forming. The emergency brake bracket, parking brake lever, and caliper mounting bracket were blasted with 80 grit glass media, and then cleaned with paint thinner before painting. I also taped off areas of the caliper and cleaned it with thinner as well.

    blasted.jpg
    ready_to_paint.jpg

    If you want to paint the calipers, you can do it now or wait until it goes back together. If you do it before reassembly, make sure to plug and block off the cylinder bore really well, and plug the brake line and bleeder ports. Also block off the brake lever boot and needle bearing. Be sure to use a good quality paint designed specifically for calipers, and expect to do some touch-up after assembly.

    For mine, I blocked off the brake lever boot and bearing with a tight-fitting plastic cap, and taped the guide pin boot area. I then painted the calipers with red Duplicolor caliper paint, and the brackets got a coat of gloss black engine paint.

    painted.JPG

    Assembly

    With everything cleaned up, coat the new piston seal with some brake fluid and work it into the groove in the cylinder bore. Next, work some high-temp lithium grease into the needle bearing, and coat the brake lever boot and lever spindle with grease as well. Fill the cutout in the spindle with grease, and then insert the spindle into the caliper. Notice that the needle bearing has an open side; this needs to be oriented toward the piston bore, and the cutout in the spindle needs to line up with this opening in the bearing. Once the brake lever assembly is in place, re-attach the brake lever return spring.

    Note: You can put the brake lever, washer, and nut back onto the spindle before assembling it to the caliper, or afterwards (which is easier). If you put the brake lever on after the spindle is inserted, put a spare bolt into the cable bracket bolt hole on the caliper to act as a stop for the lever, which gives you something to tighten the nut against. In the pic below, you can see the hole I'm referring to at the far right of the caliper, partially hidden by the brake lever.

    lever.JPG

    And now for that pesky auto adjuster assembly...

    Rather than inserting each piece one at a time and then fighting with the spring, we are going to make a temporary assembly on the bench using the bushing and clamp that we used for disassembly. Make sure the o-ring is in place on the auto adjuster spindle and coat it with high-temp lithium grease, and fill the end of the spindle with grease as well. Next slide the stopper plate over the spindle, making sure that the pins are towards the o-ring side. Next comes the spring (small end towards the o-ring), followed by the spring case. Now slide the bushing over the spindle and into the spring case, and place the vac clamp onto the spindle while compressing the spring case as far as possible. The vac clamp should keep the spring and case compressed once you release it.

    Note: On one of my calipers, the o-ring was dried out and starting to tear. I found a replacement at Ace hardware, which was 13mm x 17mm x 2mm. I was a little concerned as to whether it would hold up in the brake fluid and heat of the caliper, but I've had good luck with them before...so I went with it. Time will tell...

    Here are the parts that make up the auto adjuster assembly, after a good cleaning:

    adjuster_parts.JPG

    And here they are assembled with the bushing and clamp holding the spring compressed:

    adjuster_clamp.JPG

    Insert the small connecting link into the grease in the end of the spindle, or into the grease in the cutout in the brake lever spindle in the bottom of the bore. Either way will work, as long as the link doesn't fall over and ends up between the auto adjuster spindle and brake lever spindle like it should. I shot the following pic to show how the link will sit in the adjuster spindle end, but it's actually easier if you put the link into the lever spindle in the bottom of the bore and then install the adjuster spindle assembly down over it.

    adjuster_pin.JPG

    With any luck, you should now be able to insert the entire auto adjuster assembly into the cylinder bore while the clamp keeps the return spring compressed.

    Note: Before inserting the auto adjuster assembly, make sure that the connecting link is still parallel with the bore. Also pay attention to the two alignment pins on the bottom of the stop plate; these need to line up with the matching holes in the bottom of the bore.

    You will have to work the spindle into the bore due to the o-ring resistance, and you'll probably have to use a screw driver to line up the spring case with the lower bore as you push everything into place. Once the spring case is inside the lower bore, you can use a screw driver on each side of it to work it and the vac clamp down as far as possible. If everything goes as planned, the spring should still be compressed and you should be able to see the groove for the c-clip above the lower lip of the spring case.

    Next, compress the c-clip with the pliers and work it into place. The opening in the clip should point towards the bleeder, and it may take a few tries to get it to seat properly. If you can get it partially compressed and one side of it into the groove, you may be able to carefully remove the pliers and then use a screwdriver to finish seating it. (This isn't quite as hard as it sounds...but it will take some patience and maybe a few attempts to get the hang of it.) Once the clip is locked into place, use some needle nose pliers to remove the clamp and bushing. Then move the brake lever back and forth a few times while pushing against the end of the auto adjuster spindle, and ensure that it moves about 3/16" or so in and out as the lever is turned.

    Here is the cylinder bore with everything assembled and the clip in place:

    c-clip.JPG

    If you've made it this far without loading any weapons, the rest is cake :D

    Coat the inside of the cylinder bore with some brake fluid, and thread the piston onto the auto adjuster spindle. Use the special tool (or pliers, etc) to tighten it all the way down. You should end up with the grooves on the top of the piston oriented towards the top and bottom of the caliper. Use a bit of brake fluid to lubricate the boot, and place it over the piston and into the cylinder bore. Carefully work it into the grooves in the cylinder and the piston.

    The seal kit I used was from O'Reilly's and cost about $3. It came with a new seal, boot, and boot ring.

    seal_kit.JPG

    Mitsu sells a kit that also contains replacement pin boots, and I'm sure NAPA sells them as well. I'll update this article with more info and part numbers on these other kits when I get it.

    Getting the boot ring to sit properly in the boot can be a bit difficult the first time you try it. The boot has a "lip" on the outside edge that sits perfectly flush in the cylinder groove if it isn't stretched and is seated properly. I use a dull flat-head screwdriver to CAREFULLY work my way around the boot, pressing the lip outwards and into the groove. There shouldn't be any wrinkles in the boot, and the outside edge of it should pretty much dissappear into the cylinder.

    Once the boot is seated properly, install the retaining ring by starting at one end and working your way around the cylinder. The ring pushes against the outer edge of the boot, about 1/8" down from the top. The boot has a very shallow groove in it for the ring, which you can just barely see and feel as your working the ring into place. If you aren't careful, it's easy to get the ring under the boot edge, or to roll the boot edge over the ring. When it's correct, the ring should be about half way into the cylinder wall against the boot, and barely visible while looking straight down into the cylinder at the edge of the boot.

    Refer to my article on How to rebuild front brake calipers for more information and pics on inserting the boot ring.

    As a final check, I like to slowly inject about 5-10psi into the brake port to partially extend the piston, to make sure the boot is seated properly and isn't torn or leaking. If you do this be VERY CAREFUL and put a piece of thick wood between the piston and outer caliper wall, to prevent over-extending the boot and piston.

    Note: This may also make it easier to insert the boot ring.

    boot.JPG

    Finally...install the pin boots, grease the outside of the pin sleeves and boot lips with some high-temp lithium grease, and reattach the pins and caliper bracket to the caliper.

    pins.JPG

    A little paint touch up and some new pad clips, and it's ready to bolt back up to the car. (Oops...still need to attach that brake lever return spring that I repainted).

    done.JPG
     
    Last edited by a moderator: Jul 2, 2014

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    1992 Eagle Talon TSi AWD
    15.2 @ 89.300 · 1G DSM
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