Brake Caliper Rebuild (2 Viewers)

[Slomo]

I finally decided to tackle my front birfield repack, front and rear wheel bearings, etc and my rotors already had a pretty good warp so I finally got to replace them as well since I was in there. Mars recently did an excellent write up on caliper replacement with reconditioned units but I couldn’t find anything on rebuilding the brake calipers so I thought I would write it up in case anyone could use a good reference. It seems intimidating to many people but I think it is something any 1 - 2 banana mechanic could tackle. The benefit is that the two kits together cost less than one rebuilt caliper and each kit rebuilds both respective calipers front or rear. A little extra time spent to save a good bit of money. Tools required: Set of picks – for getting out rings and seals etc. 17 & 14 mm socket and ratchet 10mm brake line wrench 6 mm allen wrench 1 Small and 2 medium flat blade screwdrivers Air compressor with blow nozzle FSM Brake bleeder - available at Harbor Freight for $20 Parts: 04479-60030 Rear Cylinder Kit 04479-60020 Front Cylinder Kit 3-4 cans of brake cleaner Roll of paper towels Extra non moly grease, I used Redline synthetic 2 small or 1 large bottle of brake fluid This is the obvious time to do a brake fluid flush, which is often overlooked (see FAQ), as well. I first used a 60cc syringe (a turkey baster will do) to drain the reservoir. This is not necessary but it does make for a little less mess and fewer drains of the brake bleeder. I then went to each caliper and removed the two mounting bolts and used the brake bleeder to suction all the brake fluid I could by inverting each caliper independently so the bleeder valve (normally the highest point on the caliper) was the lowest. This gets the most fluid out so less will come out when you remove the pistons. Brake fluid is very caustic and damages paint so use caution. Pic 1 Front caliper mounting bolts Pic 2 Rear caliper mounting bolts closest to shock body Pic 3 Two rebuild kits from cdan, It has been said many times before but thanks for the help cdan.

 

[Slomo]

I then chose to cut the axle to caliper brake lines as I was replacing them with Slee stainless lines anyway. If you are not replacing the lines then remove the banjo fittings with a 14mm socket and take care not to loose the copper washers. You may be able to re-use them if they are not compressed too much but it is definitely better to replace them. IIRC the front kit came with replacement washers but the rear did not, not sure why, anyone? I removed all four calipers and cleaned them with brake cleaner then moved them to a bench to sit down and rebuild them. They are going to be very dirty with brake dust; mine were still so even after a generous spraying with Brakekleen. You may want to use degreaser or some form of solvent with a brush and really scrub it for less mess during rebuild but I was too lazy.

I took the front calipers and set them on a shop towel with all the tools listed above. *I recommend completely rebuilding one caliper at a time so you always have one for reference on re-assembly*. You need to remove a metal ring and rubber dust boot off of each of the four pistons in each front caliper. These come off easy with a small screw driver to push the metal ring off and a gentle pull with your fingers. Now comes the slightly tricky part of removing the pistons. The easiest way I found was to put the compressor nozzle against the end of the cut (in my case) or intact brake line or brake line opening in the caliper using a small section of tubing (1/4” rubber fuel line works well but you have to hold it into the caliper) and pop a piston out. Be sure to wrap a towel around the caliper to catch the fluid and piston as they come out with a pretty good pop and can fly onto the floor and damage the piston but won’t hurt your hand when it does pop out. This will most likely only remove one of the four so you should replace the displaced piston just enough to re-seal it in its cylinder at the level of the rubber ring and put a spacer, I used a small box, to fill the gap in front of it and re-apply the air pressure to displace another. You will need to do this for all four pistons and you may need to get creative to get each respective one out without completely displacing the rest.

1. Tools and parts for the rear on the bench.
2. This is an after shot of the front caliper but it shows the metal ring better.
3. This is a staged shot with the rear caliper to show but you should wrap a towel around the whole thing to catch the piston as it comes out and the brake fluid that will spray too.

 

[Slomo]

You can also use two screw drivers to very gently work the piston out with many short pushes back and forth side to side. You must use extreme caution so you don’t mar the sides of the piston or it will develop a leak and ruin the sealing ring in the future. Also never pry on one side only as the piston has a very precise fit and can get wedged in its cylinder and be very difficult if not impossible to get out without damage, use tiny increments side to side. Using air is the preferred method. As you remove the pistons you should place them in same order that they came out of the caliper or number them along with the caliper so they can be re-installed into the same cylinder. Once out remove the sealing rings from of each cylinder with a small angled pick, again being careful not to mar the cylinder walls. Now clean all cylinders and pistons with a clean paper towel and brake cleaner. You may need to use a pick or very small flat screw driver to get all gunk out of the piston and cylinder channels crevices. There may be some deposit that is difficult to get off the piston sides, if so you can use a razor blade and “shave” the piston side. Never use the tip of the blade and be very careful not to damage the surface, think like a razor shaving hairs with no nicks.

1. This is the two screwdriver method but be VERY careful if you do this, it really is easy to mess up the piston.
2. Using a 90* pick to remove the piston ring.
3. The removed pistons on the bench, the front left is a before and the front right is an after cleaning. I just used a clean rag, brakekleen, and a fresh razor blade.

 

[Slomo]

Now you need to install four of the cylinder rings into their respective channels in the caliper. Use the supplied lube to place a generous coating at the rings and I like to put a very thin layer on the pistons themselves as well. You will probably run out of the grease supplied with the kit which is why I used some of my synthetic grease. This will prevent damage to the piston sealing ring on insertion of the piston. Put one piston boot on each piston in its groove and carefully push each piston all of the way in. Now gently work each boot over the metal ridge of the caliper that surrounds each cylinder. Take a metal ring and place one end of it against this ridge on top of the boot and work it onto the full circumference of each of the four pistons boots holding them to the caliper. I found that it is easiest to start with one end of the ring and work circumferentially around until the entire ring is on holding the boot to the caliper. Use a flat screwdriver to carefully push each ring to ensure it and the dust boot are completely on. You can now install your new or replace your old brake pads per FSM or FAQ and repeat on the second caliper.

1. This shows two cylinders cleaned with the one on the left empty and the one on the right with the new ring installed.
2. The piston with new boot installed.
3. Pushing the boot retaining ring on completely with a small screwdriver.

 

[Slomo]

The rear calipers are a little easier to get apart but have a few more parts to replace. Start by taking the caliper halves apart. You can simply slide the non piston side of the caliper off of the guide bolts or you can use a 17mm socket and remove the guide bolts. An air gun makes this very easy on the bench or you can break them loose in a vice or break them loose before removing them from the truck to hold the caliper steady. Take a towel and wrap it around the piston side of the caliper and use the air nozzle to blow the piston out as done on the front calipers. The rears are easier in this respect since they only have one piston to remove. Use a pick to again remove the cylinder ring and clean the cylinder and piston with brake cleaner like the front. Install the cylinder ring in the inner most channel and lube it and the piston with supplied grease. Take a piston boot and slide it over the piston past the channel it normally goes in on the piston till it almost comes off the inside end of the piston.

1. The two guide bolts loosened for removal.
2. The cylinder half and the removed piston.
3. You need the boot this far up for the next step, just before it comes of the end. Make sure you orient it correctly.

 

[Slomo]

Now hold the boot/piston up to the cylinder and work the lip of the boot into the outer channel of the cylinder wall. This is a bit tricky and takes some patience. You can use a small blunt object to push the last of the boot into the channel but be very careful not to cut the boot. I accidentally poked a hole in one of the boots but it is not a major deal as the ring placed in the caliper itself seals the piston and the boot just keeps dust out which it can effectively do with a small hole poked into it. I was able to work it in almost entirely with my fingers but I have small girly hands. During this step you will have the piston and boot in your hand and the piston will not be in the cylinder at all until you get the boot in place in the outer cylinder channel. Without allowing the piston to slide out of the boot or the boot to pop out of its channel in the cylinder gently push the piston in with your finger tips. Do this very slowly and do not force it, if you do you can easily damage the boot or the cylinder wall. After getting the piston started in push it about half to two thirds of the way in and gently work the end of the boot around the piston into the channel in the brake pad end of the piston and push the piston the rest of the way into the cylinder.

1. This is how the boot and piston should look after you have the boot installed in it’s channel in the cylinder and the piston just started.
2. This is how it should look with the piston installed and fully depressed.
3. Removing the short dust boot.

 

[Slomo]

Now take the non piston side of the caliper and remove the small rubber button, short dust boot and the full length dust boot on the other side off and clean the guide bolts and small cylinders with brake cleaner. Take the dust boot and full length dust boot and install them into the small cylinders. The short one will go on easy but you may need to use a little Wd40 on the outer surface of the full length boot to get it to slide in. You can use a small blunt object to get the closed end to “pop” out the cylinder but be very careful not to poke through. It is best to wait to install the rubber button to close its respective small cylinder until the guide bolts are installed or else it might pop out due to the increase in air pressure. Use a q-tip to lube the inside of both of the small cylinders and boots as well as a thin film on the two guide bolts. Screw the two guide bolts by hand into the piston side of the caliper and gently push the other side onto the two guide bolts until the two boots “pop” onto the raised ridge of the bolts next to the other caliper half. You can then put the rubber button in its hole and you are done. Each rear caliper will have a large R or L on it to identify which side it goes on. The fronts do not have identifying marks but you can tell which is which by always positioning them so the bleeder valve is at the highest point.

Congratulations you have just saved yourself a good bit of money, learned how your calipers work and made your rig safer to operate.

1. Removing the “long” boot.
2. Reassembling the two halves just prior to the boots popping onto their seats on the through bolts. Notice the little bit of lube on the bolt and boots. Be sure to use just enough to get them on and seated.
3. The two halves installed together and the new pads being installed.

 

[OGBeno]

Its good, technically accurate posts like this that make me really love MUD.

Good job indeed. FAQ material par excellence.



-o-

 

[Slomo]

Much appreciated. Hope the roads in New Mexico are treating you and your 80 better than the ones in Ohio.

 

[KLF]

Here's a tip for getting the pistons out of the caliper, works really well, especially if you're pistons are really stuck and rusty. No amount of air pressure will get a stuck piston out, it can be a real fight. BTDT...

Before opening any brake lines or draining any fluid out, go around and pull the pins and brake pads out of the calipers (leave the calipers mounted). Then just get in the truck and stomp on the brake pedal. The hydraulic pressure will force the pistons out. Stuck or not, they will all come out if you press hard enough. Works every time!

 

[Slomo]

Excellent idea, I used a small wooden box to duplicate that but freehand on a bench, this would be much easier and everyone has the rotors.

 

[vkfzj80]

thanks for a great write up. got the rebuild kits, now I just need a some time to tackle this project

 

[LandCrusher'70]

NICE WORK!

I really need to do my brakes. I was going to replace the calipers, but now I'm gonna re-build.

Thanks Mo!

 

[rockclmbr]

Hey Slomo,

Can you post any positive improvements in braking after doing this rebuild?

 

[Slomo]

Hey Slomo,

Can you post any positive improvements in braking after doing this rebuild?

As a matter of fact I can. The braking is hugely improved. For a recap I went from factory rotors f/r, factory 80 pads f/r, ss lines from the frame to axle f/r and factory lines from axle to caliper. I now have all stainless braided, DBA slotted only rotors f/r and OEM 80 pads rear and OEM 100 series pads front. I didn't do any actual stopping distance tests prior but from the seat of the pants it is much much better. My old rotors were warped in the front and had some small heat cracking. I followed DBA's breakin verbatim and allowed them to cool fully. I have approx 250 miles on them now and am very happy. They stop much better with the same pedal pressure and they haven't faded on me yet but I haven't used them in the mountains yet either. I noticed prior that the stopping power of the brakes would reach a point where more pedal pressure made no difference, they would sort of "max" out and become mushy. I assume this is due to the gas build up between the pad and rotor but it didn't used to be so bad about a year ago. I now have a better stopping more progressive feel to just before lock up when the ABS kicks in. So after all that nonsense they are better and I am very pleased.

 

[IdahoDoug]

Beautiful posts, Mo.

DougM

 

[SOCALFJ]

Thanks for taking the time to post this.. it's truly appreciated man.

 

[Slomo]

Thanks again, glad it could be of some use. I found it very interesting to work in the innards of an often overlooked but important part. Happy others do too.

 

[turbocruiser]

Excellent Write Up Mo!!! Very easy to read, very easy to understand and with the wonderful sequential pictures, very easy to see. I have one question about the Slee SS Lines - I have the one set only but did you use / re-use the stock retaining clips for the lines or the ones that are provided with the SS? Thanks so much for taking the time to spell it all out for us. FAQ Material all the way in my opinion!!!

 

[Slomo]

Excellent Write Up Mo!!! Very easy to read, very easy to understand and with the wonderful sequential pictures, very easy to see. I have one question about the Slee SS Lines - I have the one set only but did you use / re-use the stock retaining clips for the lines or the ones that are provided with the SS? Thanks so much for taking the time to spell it all out for us. FAQ Material all the way in my opinion!!!

Thank you very much, I was hoping it would be useful and to contribute something back since I have gotten so much from this site and especially the 80 series tech section.

I used the clips that came in the Slee kit but I think you could re-use the factory clips. As far as I could see by just eyeballing them the factory clips have a little more "offset" with thinner metal and the ones that Christo uses are made of thicker metal but less "offset" and achieve the same thing. I am not sure of the technical name but by offset I am refering to the space that the clips take up when installed to hold the brake line tight in its bracket.