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Brakes 101 - Class is in!

Brakes 101 - Class is in!

Postby Murco [OP] » Nov 19 2012, 7:35pm

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 2years or 24K miles. Surprised? Most are and our owners manuals (just like every other domestic owners manual) say not a word about it, but check every Japanese or European car's owners manuals and they will recommend every 1-2 years. 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 - Some of our trucks still have these so 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. THEY ARE NOT SUPPOSED TOO!! 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. 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). To lubricate the hardware do not use silicone-based lubes, use a proper brake grease.
Calipers - 70% of your braking power is right here and most of you will have either the PBR dual piston or a Delco Moraine 78mm single piston caliper. These are a stout pieces for around town driving and the large bore of the single piston unit is fairly resistant to sediment binding when maintained properly. The dual piston versions often have the "phenolic" pistons which need replacement every 75-100k miles as they start swelling which is a good time to rebuild any caliper as the heat cycling will have started hardening the piston seals anyway. 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, pitting (numerous small holes on the pad face), and scoring (the pads look like the surface of an old LP record). I would 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 $8-12 per corner and an additional $20 per corner for phenolic pistons. 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.
Last edited by Murco on Nov 19 2012, 8:10pm, edited 4 times in total.
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Brakes 101 - Class is in!

Postby Machster69 » Nov 19 2012, 7:42pm

Wow! Thanks
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Re: Brakes 101 - Class is in!

Postby Murco [OP] » Nov 19 2012, 7:51pm

We have covered the basics for maintenance and pad/shoe problems, lets get deeper...
MASTER CYLINDER - The master cylinder is the most important part of your car!!! Think about it, it's true!
Look inside your master cylinder reservoir for a moment and look at the fluid. Does it look like apple cider, tea, or coffee? It should be a golden clear color. If it's slightly darker (like tea) it's time for a change. If it's really dark (like coffee) and there is sediment at the bottom (wet black film) you have extensive seal deterioration and need a new master cylinder, PERIOD!
How about green fluid? Never seen it? Ask a neighbor who owns a 3 year-old F**d if you can see his master cylinder. If he's like 90% of people, it's the OEM fluid and I'm willing to bet it's green! Green fluid indicates the copper in the brake fluid has started turning acidic from excessive moisture and is eating the brake-line inner coating and corroding them from the inside out. Fords do it quickly but after a dozen years or so I'll bet some of our board member's cars have this too.
Getting back to the blackened fluid - That film is particulates from the seals coming apart. Our master cylinders are made up of;
2 pistons (primary & secondary)
2 chambers (primary & secondary)
2 primary seals (named for pressure sealing, not location)
2-3 secondary seals (used for separation and sealing)
2 springs (primary & secondary piston return)
and a housing and reservior
If one of the secondary seals goes bad you will still have a decent pedal but your brakes will wear one or the other end much faster than the other. You can usually identify this problem when opening a master cylinder cap and finding one chamber lower than normal and the other near overflowing. Replace the master cylinder.
If one of the primary seals is dead you will still have brakes but with a low pedal and little stopping power. Replace the master cylinder.
If one or both of the springs are losing tension the pedal will return slowly and drag the brakes after you release pressure. Replace the master cylinder.
Also, consider replacement if you have headers and more than 50K miles on your master cylinder. The extra heat will damage the springs (heat-stress) and seals (hardening) inside the master. Our one advantage to cars is the relatively large expanse under our hoods so the exhaust heat isn't directly under the master cylinder.
ABS Pump/Module - There have been 7 different generations of the Delco/Moraine ABS unit in our vehicles over the years and fortunately the last 3 hav ebeen pretty good as far as reliability and maintenance. However, you don't want to have too replace one as the sticker on one of these bad-boys will make you cry! When you have your brakes bled have the tech use his little handy OBDII reader to cycle the ABS pump to get all of the fluid flushed through it. Other than that it's nothing you need to do much about for maintenance.
Got nasty fluid in the master or the ABS system? Guess what else needs replacement?!
Remember, gravity does it's thing with particulates too so when you find it in the master cylinder/prop valve/ABS unit you'll certainly find it in the calipers/wheel cylinders.
Their are 1000's of professional mechanics who don't know squat about proper brake repair, and I'll back that up. Think I'm pulling your chain?? The first post in this thread contains more info than is covered in an ASE MASTER CERTIFICATION exam for brakes, all 25 questions of it!!! Think about that!!!! Good luck!!!
Last edited by Murco on Nov 19 2012, 8:18pm, edited 1 time in total.
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Re: Brakes 101 - Class is in!

Postby 1500VHO » Nov 19 2012, 8:09pm

Thanks Murco!!

And welcome to the site!

This should be a sticky!

:D
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Re: Brakes 101 - Class is in!

Postby Murco [OP] » Nov 19 2012, 8:28pm

Thanks for the welcome, happy to spread the knowledge!
Now we'll sit back and watch the flames about fluid changes and wheel cylinder leaks! lol
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Re: Brakes 101 - Class is in!

Postby starspangled6.0 » Nov 19 2012, 8:36pm

Great info! Thanks for joining the site!
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Re: Brakes 101 - Class is in!

Postby 1500VHO » Nov 19 2012, 8:42pm

Flames, flames??? :lol: That is a real belly slapper...

Any leaking on the brake system is BAD! They work by hydraulic pressure. Any leak weakens the pressure the system can "see" or use. Leaks also allow air, water and contaminants in...

Didn't know about the "green" color thing, but it makes perfect sense. Copper exposed to moisture and corrosion turns green. Chemical fact! My fluid is still clear, but I will be changing it out before winter hits... Going with a good synthetic fluid. Any thoughts on that??

:D
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Brakes 101 - Class is in!

Postby Machster69 » Nov 19 2012, 8:44pm

My vote for sticky ...
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Re: Brakes 101 - Class is in!

Postby starspangled6.0 » Nov 19 2012, 8:51pm

Already sticky'd, Kyle. You're not nearly as fast as the wonder-mod :lol:
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Re: Brakes 101 - Class is in!

Postby Murco [OP] » Nov 19 2012, 8:52pm

1500VHO wrote:Flames, flames??? :lol: That is a real belly slapper...

Any leaking on the brake system is BAD! They work by hydraulic pressure. Any leak weakens the pressure the system can "see" or use. Leaks also allow air, water and contaminants in...

Didn't know about the "green" color thing, but it makes perfect sense. Copper exposed to moisture and corrosion turns green. Chemical fact! My fluid is still clear, but I will be changing it out before winter hits... Going with a good synthetic fluid. Any thoughts on that??

:D

Don't use synthetic brake fluid in a street driven vehicle, it's one of the few things our owners manual do tell you! lol
Synthetics are fine for bikes and show cars but they cannot withstand the heat cycling of a car or truck brake system. They also don't have the water encapsulation capability of DOT4 fluid so your brake components will corrode pretty quickly. Castrol LMA is the best stuff out there for street vehicles but it doesn't absorb as much water either so more regular fluid changes are needed. I've used it on street and semi-pro track cars with no issues, not even temp related on tracks were the brakes hit 1000 degrees!
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