1

I am trying to find the optimal method for brake fluid replacement, so I want to weight all possible methods (the reverse method don't consider) and use the best suited. I always used the hold/pump method, but today have read, that it can be harmful for master cylinder (I will give a link to the source, further).

So, my questions:

  1. Which method should I use, if I want to get the best result - the maximum old fluid replacement, the minimum of potential harm for the brake system, the minimum contents of air in it, etc?

  2. Is the preferred method different for different cars? For example, for Opel Astra H 2011, I should use pump/hold, but for Volkswagen Jetta 2011, I should use another? Both have ABS.


Сons of different methods, that I found:

Hold/Pump:

During this method, the brake pedal and master cylinder piston will travel beyond their normal range which can cause wear on seals or incorporate corroded metal into the brake fluid. Wikipedia. Pros and cons of different methods

Subquestion: How high the probability of this damage? Is it the real thing or just the theory?

Pressure:

If I will build up excessive pressure in the brake fluid reservoir accidentally (more then 1 atm, for example), it can explode. Also, it is hard to control the level of fluid in the system, because of cap, that covers the reservoir.

Vacuum:

Vacuum bleeding may work well if the calipers all have o-ring-type piston seals but it should not be used with caliper having OE-type lip seals because it's too easy to apply too much vacuum such that you suck air past the piston seals...which, of course, defeats the purpose of bleeding. Source

Gravity:

May be, air bubbles wouldn't expelled well, without forcing the fluid flow. Also, can air get into the calipers through the screw hole or the thread, when I will loose screw for bleeding?

2

If you use the « pump the pedal » method, then put a block under the pedal to limit its travel - this stops or reduces the chances of damaging the seals. This is golden advice on my model of car as the seals can get turned over...

A better system is to pressurise the system and push new fluid all the way through, but systems with abs can cause issues if one is not careful, and sometimes even if one is careful...

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