I found this post info else ware, and while I may not fully agree with every last minor detail mentioned , its well worth discussing the info he brings up here, and he certainly brings up several good points
Murco said:I worked as a technical consultant for Bendix training technicians for a few years and hopefully this thread will help with some basic and a few more advanced diagnostics and repair procedures for those who want to work on their brakes. This is mostly for disc/drum systems but drum/drum systems use the same information.
Let's start with the basics...
First and most importantly - USE THE HIGHEST QUALITY PARTS YOU CAN AFFORD!!! These are your brakes, the number one safety feature of your car. If the car doesn't run, you won't die. If your brakes don't work, you can get killed or injured! Don't skimp on the brakes!
Brake fluid - You must replace it every 24K mile or once every other year, more if you live in really humid areas (like Florida) or if your car sits a lot in the winters. Brake fluid is similar to motor oil in that it is designed to encapsulate the moisture and sediment in brake systems but it only has so much capacity to do so. As it ages the boiling point drops, deposits collect, and problems start becoming more expensive to correct. Flush and bleed the brakes after every other oil change and you'll avoid 70% of common brake issues. I recommend DOT 4 fluid or Castrol LMA fluid (low moisture absorbtion) as it has a higher temperature rating and is less suceptible to breakdown in high-performance use.
Wheel cylinders - If you have drum brakes on your car and over 15K miles on them I will bet the wheel cylinders are either leaking or sticking. I'll also bet alot of folks here think they are supposed to leak and operate just fine like that. Tea, not so much... Wheel cylinders operate at far higher pressures than calipers just to open the return springs, much less stop the car. Peel back the dust boots on the ends and if you find any brake fluid at all (assembly grease is OK) go ahead and replace them, they're cheap! Often, wheel cylinders will blow their seal during a hard stop, squirt tiny amounts of fluid, then draw air into the lines when you release the pedal. This essentially renders rear drum brakes useless on a disc/drum car, overworking the fronts causing excessive heat, wear, and dramatically increased braking distances. It will also cause spongy brake pedals, more so on drum/drum cars. If you have the hardware off check to see if the cylinders move freely back and forth, about 1/4" of travel. If they stick, replace them, it's cheap insurance!
Hardware - Anytime you replace pads or shoes replace the caliper hardware and/or return springs as well. These items are cheap and allow the system components to slide and return properly. Worn caliper hardware will cause uneven pad wear from the leading-to-trailing ends. Worn return springs will cause heel-toe shoe wear (different wear in leading and trailing shoes).
Calipers - 70% of your braking power is right here and most of you will have the standard 78mm single piston GM mid-size caliper. These are a stout piece for around town driving and the large bore is fairly resistant to sediment binding when maintained properly. For high-performance use they are marginal at best but this is a maintenance and repair thread so lets fix what you have. The most common problem afflicting calipers is sediment bind due to poor maintenance. The heat cycling calipers go through is staggering and the large-bore calipers tend to "cook" the fluid under heavy use and flushing the fluid yearly is essential to keep these working well. Binding is diagnosed through the pads, look for uneven wear side-to-side, pitting (numerous small holes on the pad face), and scoring (the pads look like the surface of an old LP record). I would strongly recommend rebuilding the ones on your car before getting remans, no matter how cheap they are. Why? Your's have been in service recently, you know their history, and they haven't been sitting in a junkyard for who knows how long awaiting rebuild while exposed to the elements. It's also very inexpensive, about $5 per corner! You would probably be stunned if you opened a reman caliper for an older car. Many will have heavy corrosion pitting on the piston, scored bores, corrosion scarring, and heli-coiled line and bleeder threads. None of these conditions are acceptable your brakes shouldn't have these issues. I'll back this up later this month when I rebuild the calipers on my daily driver, they were "professionally" replaced just before I bought it in November and I bet they are needing complete replacement. Why? Because the shop didn't bleed the system (black fluid in the master cylinder) and the brakes are spongy... Oh, those "professionals"!!!