Quote:
Originally Posted by cdcox
1. Yes.
2. Don't recall. But lets assume yes to cut the 20 question short. How is that air entering the system? Is it always vented through the reservoir?
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That isn't air entering the system, that is actually the main source of where exits the system. In order for a system like this to work (The Modern Power Assisted ABS Braking System), you have to either have a source of pressure, or a source of vacuum to "move" the fluid through the system.
Furthermore, you have to be able to "alleviate" the pressure required to adequately stop the car from moving, without making you strain yourself.
Enter the wonderful contraption that is "power" brakes and the vacuum booster. For brakes to function properly, fluid has to actually cycle through the system. It cannot just sit stagnantly, as this causes excess wear and breakdown, and can further harm braking components should a contamination arise.
Anyways, the reason you feel the pedal get stiffer and stiffer as you pump the brakes in your car, is because you have no actual vacuum. The Check valve is operating to allow any air to be pulled out of the vacuum booster which no longer functions to amplify pedal force to the brakes. In this sense, not only is it harder to brake, but because of the other vacuum functions applied to your braking system, fluid is stagnant and the system is not functioning properly.
I'm not going to go into detail on the 35 other contraptions and functions added to power assisted brakes over the years, like ABS, prop valves, etc. But rest assured, there are many ways for the system to relieve pressure air pressure, and the common way is through the master cylinder after pumping that air bubble all the way through the maze that is your brakes.
On top of this, all cars are designed so that fluid from the master cylinder reaches the calipers almost simultaneously under the event of a malfunction.
What this means is, almost every car has brake lines nearly the EXACT same length, and in performance applications EXACT to the .00001th inch.
The reason for this is quite simple. If suddenly there is a loss of "pressure" in the braking system and air and fluid have mixed, the system is designed to bring air in, and "compress" to move the fluid furthest down the pathway to the calipers to assist in any way as a last minute "failsafe" to provide braking force.
This does not always function the same, and almost never functions in an environment where you have 4 brakes working properly, but instead the system will try to "source" out the "bad" brake.
In a sense you've got Left Front, Right Front, Left Rear, and Right Rear. If the Right Rear is bad, the braking will try to apply itself to the Front Right and Front Left with minimal braking to the rear. This is done through valve bodies in the braking system monitored additionally by your ABS system. It does this to prevent A. A wheel from locking up, and B. The care from braking too harshly on one side or the other.
My point from the start, is that you are "messing" with a fail safe by reducing the length of the specifically measured and crafted brake lines. I didn't realize some jerkoff shadetree mechanic was going to come in and act like he knew everything about my job and industry practices and disagree with me on topics that aren't even subject to his expertise.
Lastly, Brakes are not just Brakes. Cars are no longer Legos like Shadetree would like you to believe, the systems in these cars are so technologically advanced and complicated that it takes smart individuals with degrees and certifications to go through school so they can understand the "W's" of functionality, so that when shit hits the fan, things get fixed and taken care of.
Hope that explains everything for everyone. My PM box is open if any of you have questions, please do us all a favor and have your cars worked on my professionals if you think the skill required is above your ability, and when you are looking for a good mechanic, make sure they have certifications AND experience, not just one or the other.
I won't be replying in this thread any further unless Mr. Shadetree decides he's going to start answering my questions about his ASE Certs.