Per Jim Millet, 3/15/2005 Not too difficult a job. Rears are easier than fronts to access. You ll need the following gasket sets: Front caliper gasket set, P/N 34 11 1 157 037, MSRP $13.58 Rear caliper gasket set. P/N 34 21 1 158 578, MSRP $17.50 Some folks also replace the guide bushings, P/N 34 11 1 157 038, MSRP $12.67. The brand name to get is ATE (ah -tay). You ll need a 14mm (13mm for stainless lines) flare wrench to break loose the brake hose from the caliper housing and you ll need a 14mm (13mm) crows foot to torque the brake hose to 17-19 N*m. You ll need some compressed air to blow the piston out of the caliper housing. I wrap the caliper in an old towel so I don t blow brake fluid all over the place. I use Gumout Carb & Choke Cleaner to clean up the caliper and alcohol and compressed air for the final cleaning of the caliper housing cylinder and piston. The trick is to get the new dust boot seated in the caliper housing prior to pushing the piston into the cylinder. The below procedure works for me. Brake Caliper Rebuilding Tips First tip: I think it was Pat Donahue who gave a tip about covering the master cylinder with plastic wrap when removing the calipers to keep the fluid from leaking out. This works, but I found it was difficult to get a perfect seal with the flimsy plastic. I ended up using the palm of a latex glove purchased at an auto parts store under the cap of the Motive Power Bleeder. About four drops of fluid leaked out in all. Tip II: Removing the piston is best done with an air tool. There is an attachment for air hoses available that is perfect for this purpose. It's simply a nozzle with a pointed rubber tip and a trigger handle. The rubber tip creates a seal in the hose fitting. I read several instructions on web sites (thanks to all who maintain that type of stuff for us) that mentioned blowing air into the fitting for the brake line of the removed caliper to force the piston out, but they didn't mention the tool. I've tried the pumping the brakes with the calipers removed from the brackets but still attached to the lines, but that can get brake fluid all over everything as well as damaging your master cylinder when the pedal goes to the floor. Wrapping the caliper with a rag and placing a block of wood under the pedal is a must if you do it this way. The air tool is much easier. When using the air tool, everyone said to use a block of wood to catch the piston in order to prevent it from flying across the garage and damaging the piston. Good idea. However, I'll add that it's a must to wrap the caliper with a rag along with using the piece of wood under the piston. There will be a small amount of brake fluid left in the caliper. Under pressure, it will fly. And although I am a hack, I hate seeing machined hydraulic parts flying towards other metal parts at high speed without protection. When you wrap the caliper, stuff a bit of the rag in between the wood and the piston - helps keep things from getting dinged. Using the air tool, the piston pops out in a second. This is the way to go if you have an air source within walking distance. Tip Three: Those cheap, simple caliper spreaders used to press the pistons in during pad swaps work really well for installing the piston. I've tried a C clamp, but there's not a good flat surface centered on the piston to use. You always end up with a little tilt that forces you to start over. Using the spreaders to reinstall the piston worked flawlessly. Use an old pad to spread the force over the piston.
page 2 Tip Four: The Tricky Step Installing the outer rubber booties can be a major PITA if done incorrectly! I don't know how the ace mechanic does this, but I settled on this way after tearing one boot up (yes, I buy spares when I'm doing the work). Installing the boot is easy when there is no piston in the caliper. Installing the piston is easy when there is no boot. And therein lays the quandary. What I found works very well is to install the boot on the piston first. Slide it down from the open end of the piston to the closed end of the piston. Extend the boot down so it's hanging off the end of the piston. The end of the boot that seals around the piston will be inside out at this point. Now you can fit the ridge of the boot that seals to the caliper into the slot on the caliper rather easily, since the piston is still not in the caliper. Now press the piston in the caliper with the spreader. As you go, slide the boot up the piston. When the boot reaches the slot at the top of the piston, the little ridge will pop in the slot reversing itself to right side out and you're done! No more ugly looking bulges in the boots or wondering if the boot is sealed properly all around where you can't see. Another Explanation (source unknown): For reassembly the key trick to know is how to install the dust boot. Lube the caliper bore and piston seal with a little brake fluid on your finger. With the new seal assembled to the piston, and the piston out of the caliper bore, fit the dust boot to the piston (get the orientation right). The dust boot is normally folded, accordion style. Extend it fully in the direction of the caliper. You're now holding the piston at its outside end, and the inside end of the piston and its seal are hidden under the extended dust boot, which sticks out past the piston's inner end. Now with your finger, seat the outer rim of the free end of the boot into the corresponding groove in the piston bore, WITHOUT pushing the piston itself into the bore. You should now be holding the still free piston, which is joined to the caliper body only by the installed dust boot. Now line up the piston and push/twist it into the caliper bore, allowing the dust boot to fold up again. Tap it gently in with a soft mallet if necessary. The issue here is that with the piston already in its bore there's not enough clearance to get the boot's rim into its retaining groove. That's why the piston has to come out and the boot be seated first. This may sound obscure, but once you have the parts in hand it should make sense. AND another (source unknown) explanation on installing caliper seals: 1. Attach boot to piston FIRST -- This is the key! 2. Lubricate caliper well with something (brake caliper lubricant is best, #2 is brake fluid). 3. Now, bring piston/boot "assembly" close to caliper, and fit the boot into the caliper. You want to get it so that when you place the piston into the caliper, the piston keeps the boot from coming back out. Slowly push the piston into the caliper -- the better you lubed it, the easier it is to push it against the caliper/piston seal. As I recall, I believe these are my next steps: Pull the dust boot over the outside of the piston and let it ride about halfway down the (polished) sides of the piston. I don't think that will "overstretch it". This keeps it from being too much "pull" on the boot and will allow you to place the outside lip into the caliper and not have it pop out immediately. Then, as you sink the piston down into the caliper bore, pull the dust boot up, and eventually it (the inside lip) will pop into place on the top of the piston. Miscellaneous: The air tool is also great for cleaning out the caliper. High pressure air will get out tiny bits of dirt that you can't see or feel. Use it to clear the line fitting and bleeder fitting as well as generally around the inside of the caliper. Latex work gloves are also a must for this work. A fresh clean pair when performing the final cleaning of the caliper ensures you won't leave any dirt, grime, oils, etc. in the caliper. Clean is good for caliper work.
page 3 Pictures from Ron Stygar s Let s Brake It Source: http://www.unofficialbmw.com/e36/brakes/e36_lets_brake_it.html Note: This is an excellent source for anything brake related for an E36 BMW, including part numbers, MSRP prices, and the OEM install procedures. Below are just some pictures/procedures for rebuilding the brake calipers. Again, go to the above web site for the complete info.
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