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I recently finished overhauling several sets of brake parts for various listees. In looking at the parts that I was sent, I was reminded of a number of things that can go wrong or that people can do incorrectly, so I decided to try to write up some hints for those of you who felt motivated to do some of this work yourselves. Please read over these notes. I'd be glad to make corrections or debate opinions on any of it, and if there are topics that I've missed I'll be glad to add them to the notes. Like my other writeups, this will be available as a file on request. It may be posted anywhere as long as credit is given and my copywrite notice is intact. Here they are: ******************** Brake Notes Changing Brake Caliper Pads. More damage is probably done when changing brake pads that at any other time. Here are a few hints that might save you some grief. When you replace brake caliper pads you will need to push the pistons back into the caliper body. As you do this, brake fluid will get displaced from the caliper to the reservoir. If you have been topping up the reservoir as the fluid level went down, the reservoir will overflow now. Save yourself some trouble by sucking excess fluid from the reservoir before you start. Standard brake fluid will lift paint, so be careful not to spill it on your car. The good news is that it is completely water soluble, so flushing it off quickly with water is the best way to go. To remove the old pads, start by driving out the retaining pins with a narrow punch. Remove both pins and the anti-rattle spring. Leave the old pads in place for now. Now take a pair of large channel locks and use them to squeeze one pad at a time back against the piston, forcing it back into the caliper body. The point here is to use the old pad to protect the face of the piston and the important rubber boot that surrounds it. Once you've pressed the piston in as far as you can this way, you can switch to some kind of prying tool to lever between the rotor and the pad and press the pad all the way in. You can remove the pads after the pistons are all the way back in the caliper body. Now look in there and rub your finger around the piston, pushing the rubber boot back into place. Inspect the boot. If it is cut or torn you need to stop right here and rebuild the caliper, replacing the boot. Make sure that the piston alignment plates are there and installed properly. Slide the new pads into place. They should go in by hand, but if they are tight you must not hammer them in. If you hammer them in they will bind and not release properly. If they are tight you will need to file off the flash on the upper and lower edges of the backing plates. It's extremely common to have to do this; I do it to every set of pads I install. There are many kinds of materials sold to make brake pads not squeal. I've not found a single one that works. NEVER paint the backs of pads with that gooey stuff that is sold to cure brake squeal. It will glue the pad to the rubber boot and tear the boot as the pad moves inward. Never paint the backs of the pads with anti-seize. It will attack the boots and lead them to an early death. Bleed Valve Caps Our cars all came with little rubber bleed valve caps on each of the bleed valves when the cars were new. These are more than a cosmetic touch. Bleed valves with no caps are MUCH more apt to rust in place than those with caps. I have NEVER broken off a bleed valve that came to me with a cap still in place. Brake Material Compatability For reasons I can't explain, but which must be shrouded in history, brake fluid is not a petroleum product. In addition, the "rubber" compounds (there are actually 4 different ones) used in brakes are all incompatable with petroleum products. If you get petroleum products on any brake part, the rubber will absorb the oil and swell up. This usually requires replacement of the rubber part. This goes for ALL the rubber parts associated with brakes, from seals and boots to hoses. I use a silicone fluid as a rebuild lubricant and a silicone grease in places where I hope to minimize water intrusion and the resulting corrosion. Silicone Brake Fluid I recommend DoT-5 Silicone Brake Fluid for our cars, as I am now convinced that I get much longer brake part lifetime from it than from standard DoT 3 or 4 fluids. I've been using DoT-5 Silicone Brake Fluid in all my VWs since 1978. I have a separate Silicone FAC if you're intested in more information. Brake Pads I don't have any particular preferences in brake pads. I've gotten very good mileage out of very cheap pads. I dislike pads that are rivited to the backing plates, but I've seen very few of these. The best pads have a special thin (1-2 mm) layer of damping material bonded to the back of the pads. The OE pads were like this, and these pads generally don't squeal. Rear Brake Shoes Type 3s and 4s use the same rear shoes. I believe there is a Super Beetle that also uses these shoes, nevertheless they are getting hard to find at times. When you change rear shoes you will probably notice that the front shoes are more worn out than the rears. This is simply because of the fact that the front shoes are "leading shoes" while the rears are "trailing shoes." Leading shoes have a self energizing action which makes them do more work and wear out faster. If you find that only your leading shoes are worn out, just replace the 2 leading shoes and save the other half of your set for your next brake job. Rear shoes tend to last a very long time anyway. Rear Brake Cylinders Any time you service the rear brakes it is a good idea to give a little attention to the rear cylinders. If they seem to be working fine, just wipe off the boots and remove the boots and pistons. I put a dab of silicone grease on the inside end of each piston and put the piston back in place. If the rear cylinders have been leaking or are sticking you may want to hone them. It is actually quite easy to hone them right in place and let the brake fluid drip out, flushing away the honing debris. Use clean paper towels to wipe off the internal parts and to wipe out the cylinder, then reassemble. This process only takes 10 minutes per side once you have the drum off and all your tools and parts in place. Reassemble the parts with a little dab of silicone grease on the inside end of the piston, as above. Bleed the cylinder once you're done. No need to pump: Just open the valve until the fluid comes out without bubbles. Bleeding Your Brakes You should never need to bleed your brakes unless you are flushing in fresh fluid or have just worked on your system and need to get the air out. There are many ways to bleed and almost all of them work. Some are just a lot less work. You really DON'T need to open and close the bleed valve at every pedal stroke, but it certainly helps to put a hose on the bleed valve and feed the other end of that hose to the bottom of your bleed bottle. You DON'T need to "bench bleed" a master cylinder. It doesn't help a bit and it sure makes the job a lot messier. If you have gone over your complete system and are pretty sure that everything is in good shape, then the EASIEST way to bleed is to just pour fluid in the reservoir and open one bleed valve at a time until no more air comes out. I usually go all around the car twice. This goes a little more slowly because you're only getting gravity feed, but it's a lot less hassle and a lot less climbing in and out of the car. Either way, all the air will be out of the system when you're finished. Remember to put the bleed valve caps back on when you're done. Jim Adney, jadney@vwtype3.org Copyright 7/'04 -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org