I just spent way too many hours rebuilding a rear caliper. I wanted to document the process before I forget exactly what has to be done to get these thing apart and back together correctly. I had pulled the left rear caliper off the maroon GT because it was completely frozen. I knew I had a working one that I had pulled off the black GT when I went to the rear Wilwood setup. I installed it to find out quickly it was leaking brake fluid right out the rear seal. Time for internal look.
1. In vice pull the emergency brake spring off with pliers, and remove the 17mm nut underneath the spring. Do not try pull the shaft/lever out yet!
2. Unscrew the brake piston (counter clockwise). I use a narrow wrench around a 15 mm to turn. If the piston is rusted in (frozen) a pipe wrench works well to free up the piston. If the piston is frozen the chance of the piston being re-usable is very slim. Either way if you tighten the pipe wrench up around just the head of the piston it doesn't do too much damage to the sealing part of the piston.
3. Once you unscrew the piston all the way you can carefully pull the piston out of the dust boot seal. Spray a little around the sides of the dust boot before sliding the piston out.
4. Once the piston is out you can remove the piston dust boot seal. If it is frozen into the seal bore try using some nylon picks after spraying it down with penetrating fluid or oil.
5. With the piston dust boot out you see the front piston seal. This should be removed with a nyon pick or simlar tool. I found this came out intact even in a badly corroded caliper.
6. With the piston front seal out you can see down the insides to see the first snap ring. None of the snap tool will reach this. You can use really thin flat head screw driver and wedge it in behind the head of the snap rings. With a second screwdiver at angle wedge it under the head of the snap ring and pop it up. It take a little practice. I would wedge/pry both sides of the snap ring a few times to free the snap ring up from the channel and narrow the spread of the snap ring.
7. With the first snap ring out you can pull spring with spring housing out. If the caliper is badly rusted spray the inside with some brake clean several times to start dislodging the rust build up.
8. Underneath the spring housing is a washer; remove it be flip the unit upside down or grab it with a needle nose pliers.
9. Underneath the spring housing edge is another snap ring. You can use the same method above, or you can use a really long straight pliers ground down to fine point that will fit in the tiny snap ring head holes (standard snap ring pliers will not fit in the diameter of the hole). The Channel Lock Snap Ring pliers fine ends will fit, but it won't reach to the bottom. Either way remove the 2nd snap ring.
10. Underneath the 2nd snap ring is a plate that fits around the center spiral thread rod that screws into the backside of the piston. To remove the plate I found it is as easy as screw the piston back into the thread spiral rod and pry up on the piston using something to create a fulcrom next to the caliper open edge (I used a wood handle of a hammer, and a large flat head screw driver). This will pull the rod and the plate out together along with an o-ring rear seal. At the base of the sprial rod is a cup that small rounded rod fits into. Be careful not to loose that small rod if it comes up with the cup.
11. Pull the small rod out if it didn't come out.
12. Now you can pull the e-brake rod out the back of the caliper housing. Also remove the rear dust boot that goes aroudn e-brake rod/lever.
13. Inspect all parts carefully. The caliper that was functional that I had bought a while back as a remanufacture caliper from Rockauto was never rebuilt correctly. One it was missing the outer snap ring and they had pitted the metal landing where the e-brake rod dust boot seals around when they media blast the original part. I had to sand down the rod as best I could working up to a 1500 wet/dry sand paper.
14. I hammered all imperfections out of the snap rings and lightly filed their edges before re-using (top and bottom side). If you can find matchng new snap rings I would definitely recommend that. I also used the Channel Lock snap ring pliers and spread the snap rings back out a ways. Failure to to these steps will result in a lot wasted time.
15. There is one source of rear caliper brake rebuilds on Ebay. I'm not even sure if they are correct. I'm ordering them. It looks like it comes with two pistons, two piston dust boots, two piston seals, two o-rings, hopefully two rear dust boot seals. I'll update when the kit comes in and verfiy that it is correct. It is not cheap.
16. The rear o-ring was the culprit on rear caliper that I opened. I cleaned everything down and put a new o-ring on before starting the install. Make sure you clean out the channels where the snap rings go.
17. I used some white lithium grease on the e-brake parts, the rod hole, and the spiral rod cup, and the rod itself.
18. Align the spiral piston rod so the plate dowel pin lines up with the hole on the caliper itself. Failure to do this will result in lots of wasted time. I did do this, but failed to cleaned off the extra grease that prevent the dowel pin going all the way down in the hole. Once the plate is dowel pin is in the hole and the spiral rod is correctly aligned lightly tap on the end of the spiral piston rod. I found that it moved in about a 1/16" more and this was enough to waste hours and hours of time.
19. With spiral piston rod and the plate seated correctly make sure you can fully see the first snap ring groove just above the top of the plate. If not something is not seated fully.
20. Carefully lightly guided the snap ring down. Easier to have the opening face the open end of the caliper. Use the same long narrow flat head screw driver to bend the snap ring heads in on both sides to pass by the first snap ring groove. Lightly tapping down in a circle sort of like installing a tire pattern the snap ring should pop right in place. Don't forget to put the small washer in above the plate.
21. Next verify that the spring housing end is flat; if it is not you can light tap on the top if it is on a solid flat surface to help re shape the ends or use a flat punch. Lower the housing with the spring in it into the caliper around the sprial piston rod. Carefully lightly guided the snap ring down to rest on top of the spring housing end.
22. Use a 9/16 or even 1/2" (1/2') deep socket and place the 1/2" end over top of the spiral piston rod and directly on to the top of the spring housing. Using a large c clamp tighten down the 9/16" socket onto the spring housing using the thread end of the c clamp on the socket. The other end of the c clamp fits around the flat bottom end of the caliper. Slowly tighten until the spring housing bottoms out (don't over tighten it). You can then use the same long handle thin flat head screw driver and push down on snap ring work around in a circle which if the prep is donw will snap easily into place.
23. Install the piston seal with some grease that is safe for o-rings. This was easy to do. If the rebuild kit has the correct part I would always replace.
24. Next apply of o-ring saft grease all over the dust boot sealing surface and lightly coat the piston.
25. Slide the dust boot over the head of the piston making sure you have it the right way. Pull the dust boot all the way past the dust boot channel until the dust boot is almost off the piston, but not too far.
26. Holdoing th piston above the hole work the dust boot channel into its own groove in the caliper bore. Don't let the caliper slide back down or pinch the boot. It takes some finesse.
1. In vice pull the emergency brake spring off with pliers, and remove the 17mm nut underneath the spring. Do not try pull the shaft/lever out yet!
2. Unscrew the brake piston (counter clockwise). I use a narrow wrench around a 15 mm to turn. If the piston is rusted in (frozen) a pipe wrench works well to free up the piston. If the piston is frozen the chance of the piston being re-usable is very slim. Either way if you tighten the pipe wrench up around just the head of the piston it doesn't do too much damage to the sealing part of the piston.
3. Once you unscrew the piston all the way you can carefully pull the piston out of the dust boot seal. Spray a little around the sides of the dust boot before sliding the piston out.
4. Once the piston is out you can remove the piston dust boot seal. If it is frozen into the seal bore try using some nylon picks after spraying it down with penetrating fluid or oil.
5. With the piston dust boot out you see the front piston seal. This should be removed with a nyon pick or simlar tool. I found this came out intact even in a badly corroded caliper.
6. With the piston front seal out you can see down the insides to see the first snap ring. None of the snap tool will reach this. You can use really thin flat head screw driver and wedge it in behind the head of the snap rings. With a second screwdiver at angle wedge it under the head of the snap ring and pop it up. It take a little practice. I would wedge/pry both sides of the snap ring a few times to free the snap ring up from the channel and narrow the spread of the snap ring.
7. With the first snap ring out you can pull spring with spring housing out. If the caliper is badly rusted spray the inside with some brake clean several times to start dislodging the rust build up.
8. Underneath the spring housing is a washer; remove it be flip the unit upside down or grab it with a needle nose pliers.
9. Underneath the spring housing edge is another snap ring. You can use the same method above, or you can use a really long straight pliers ground down to fine point that will fit in the tiny snap ring head holes (standard snap ring pliers will not fit in the diameter of the hole). The Channel Lock Snap Ring pliers fine ends will fit, but it won't reach to the bottom. Either way remove the 2nd snap ring.
10. Underneath the 2nd snap ring is a plate that fits around the center spiral thread rod that screws into the backside of the piston. To remove the plate I found it is as easy as screw the piston back into the thread spiral rod and pry up on the piston using something to create a fulcrom next to the caliper open edge (I used a wood handle of a hammer, and a large flat head screw driver). This will pull the rod and the plate out together along with an o-ring rear seal. At the base of the sprial rod is a cup that small rounded rod fits into. Be careful not to loose that small rod if it comes up with the cup.
11. Pull the small rod out if it didn't come out.
12. Now you can pull the e-brake rod out the back of the caliper housing. Also remove the rear dust boot that goes aroudn e-brake rod/lever.
13. Inspect all parts carefully. The caliper that was functional that I had bought a while back as a remanufacture caliper from Rockauto was never rebuilt correctly. One it was missing the outer snap ring and they had pitted the metal landing where the e-brake rod dust boot seals around when they media blast the original part. I had to sand down the rod as best I could working up to a 1500 wet/dry sand paper.
14. I hammered all imperfections out of the snap rings and lightly filed their edges before re-using (top and bottom side). If you can find matchng new snap rings I would definitely recommend that. I also used the Channel Lock snap ring pliers and spread the snap rings back out a ways. Failure to to these steps will result in a lot wasted time.
15. There is one source of rear caliper brake rebuilds on Ebay. I'm not even sure if they are correct. I'm ordering them. It looks like it comes with two pistons, two piston dust boots, two piston seals, two o-rings, hopefully two rear dust boot seals. I'll update when the kit comes in and verfiy that it is correct. It is not cheap.
16. The rear o-ring was the culprit on rear caliper that I opened. I cleaned everything down and put a new o-ring on before starting the install. Make sure you clean out the channels where the snap rings go.
17. I used some white lithium grease on the e-brake parts, the rod hole, and the spiral rod cup, and the rod itself.
18. Align the spiral piston rod so the plate dowel pin lines up with the hole on the caliper itself. Failure to do this will result in lots of wasted time. I did do this, but failed to cleaned off the extra grease that prevent the dowel pin going all the way down in the hole. Once the plate is dowel pin is in the hole and the spiral rod is correctly aligned lightly tap on the end of the spiral piston rod. I found that it moved in about a 1/16" more and this was enough to waste hours and hours of time.
19. With spiral piston rod and the plate seated correctly make sure you can fully see the first snap ring groove just above the top of the plate. If not something is not seated fully.
20. Carefully lightly guided the snap ring down. Easier to have the opening face the open end of the caliper. Use the same long narrow flat head screw driver to bend the snap ring heads in on both sides to pass by the first snap ring groove. Lightly tapping down in a circle sort of like installing a tire pattern the snap ring should pop right in place. Don't forget to put the small washer in above the plate.
21. Next verify that the spring housing end is flat; if it is not you can light tap on the top if it is on a solid flat surface to help re shape the ends or use a flat punch. Lower the housing with the spring in it into the caliper around the sprial piston rod. Carefully lightly guided the snap ring down to rest on top of the spring housing end.
22. Use a 9/16 or even 1/2" (1/2') deep socket and place the 1/2" end over top of the spiral piston rod and directly on to the top of the spring housing. Using a large c clamp tighten down the 9/16" socket onto the spring housing using the thread end of the c clamp on the socket. The other end of the c clamp fits around the flat bottom end of the caliper. Slowly tighten until the spring housing bottoms out (don't over tighten it). You can then use the same long handle thin flat head screw driver and push down on snap ring work around in a circle which if the prep is donw will snap easily into place.
23. Install the piston seal with some grease that is safe for o-rings. This was easy to do. If the rebuild kit has the correct part I would always replace.
24. Next apply of o-ring saft grease all over the dust boot sealing surface and lightly coat the piston.
25. Slide the dust boot over the head of the piston making sure you have it the right way. Pull the dust boot all the way past the dust boot channel until the dust boot is almost off the piston, but not too far.
26. Holdoing th piston above the hole work the dust boot channel into its own groove in the caliper bore. Don't let the caliper slide back down or pinch the boot. It takes some finesse.
