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1990 Opel Corsa brake fluid bleeding

Tiny
XCHCUI
  • MEMBER
  • 1990 OPEL CORSA
  • 1.4L
  • 4 CYL
  • FWD
  • MANUAL
  • 230,000 MILES
Hello.

I usually change the brake fluid with one more person that sits in the car and pump the brake pedal.
In order to do this job without assistance, I would like to know:
If I open the wheel cylinder nipples and let the old brake fluid, flow out of the system(into a bottle) by gravity,
will ALL the brake fluid in the system flow out?
At the image of the dual master cylinder that I attached, it looks like that the brake fluid in the circle parts, which I marked as A and E, will not flow out.
Will the brake fluid in those parts(A and E)really stayed in the master cylinder or will they, also, flow out of the system?
I know that usually, it is better to add fresh brake fluid to the reservoir during the process and not to let the fluid in the reservoir get down too much(air in the system)but I prefer to take out all the old fluid before adding fresh one.(Prevent mixing old and new fluid).
So, after the system is all empty of fluid(?For now, I don't know if it is all empty) I will add new fresh fluid(let it flow by gravity through the nipples)while the fresh fluid will push the air out.
Am I right?Will it work?
It will take much more time compare to the job with two people, but besides the time, are the results of the two methods(one person vs. Two person) the same quality?
I know that there are special tools(pumps. Etc)but I more interest in the process that I mentioned above.

Thanks in advance.
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Saturday, August 2nd, 2014 AT 9:06 AM

9 Replies

Tiny
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  • MECHANIC
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Use this method:

http://www.youtube.com/watch?v=MfTmlOZbXgs
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Saturday, August 2nd, 2014 AT 9:36 AM
Tiny
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Thanks for your reply, but unfortunately, you didn't answer to any of my questions. As I said, I know that there are some other methods, but my questions refered to that special method.
I will very appreciate if you can answer to my questions.
The most most important one was:

". Will ALL the brake fluid in the system flow out?
At the image of the dual master cylinder that I attached, it looks like that the brake fluid in the circle parts, which I marked as A and E, will not flow out.
Will the brake fluid in those parts(A and E)really stayed in the master cylinder or will they, also, flow out of the system."
Again, this is the most important part that I trying to figure out, all the rest is insignificant compare to that question.

Thanks in advance.
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Saturday, August 2nd, 2014 AT 10:36 PM
Tiny
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The fluid in the "A" and "E" areas will not flow out if you leave the bleeder screws open.
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Sunday, August 3rd, 2014 AT 5:52 PM
Tiny
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It seems that even if I make the ordinary bleeding process with an assistance, the parts A and E will never be changed by new brake fluid. It looks like that the old fluid in this parts will mix with the new fluid that I will add to the reservoir during the pumping process and the during the movments of the piston forward and backward.
Am I right?
Is there any simple action that can be done in order to empty that parts without any dismantle?

Thanks.
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Monday, August 4th, 2014 AT 5:45 AM
Tiny
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  • MECHANIC
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Actually during the bleeding process the fluid in those areas WILL be drained from the reservoir. (However if you simply leave the bleeder screws open it will not drain) Here's how it works:

As the master cylinder piston is pushed forward (brakes applied), the fluid in front of the piston is pushed down the brake lines to the calipers and/or wheel cylinders. Meanwhile, the as the piston moves past the Equalization and Fluid Intake & Return Ports, fluid from those ports fill the area behind the piston (areas "A" and "E" to prevent air from entering the cylinder).
Once the brake is released a spring starts to push the pistons back toward the start position. However, the spring pushed the pistons back faster than the fluid can return from the brake lines, so the seals (first and second circuit seals) on the pistons are designed to flex forward exposing holes in the piston previously covered by the seals. Brake fluid from areas "A" & "E" flows through those holes to the front of the pistons (area where the springs are) to prevent air from entering that area. As the pistons continue to move backwards, fluid from the reservoir flows through the Equalization and Fluid Intake & Return Ports into areas "A" &"E, " again to prevent air from entering.

So, you see, if you bleed the brakes by pumping them, the fluid in areas "A" & "E" will flow out and you can get the system filled with clean brake fluid.
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Tuesday, August 5th, 2014 AT 6:21 PM
Tiny
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Thanks, Freemba.
This is what I was assuming, that the fluid will stay in that parts if I only open the bleeders screw.I thought that, maybe, there is a kind of physics law that if the fluid is, already, in a flowing process, so maybe this movement will pull up the fluid from that part(E and A). But it seems, there isn't such a physics law, so the best way is remain the pumping method.
By the way, I know all the theory a bout the process as you explained, but as I said, even in the pumping method you don't take out the old fluid and put new one, you, actually, mix the old fluid with new one during the pumping process(kind of diluted the old fluid), and this is what I tried to prevent, I wanted to fill it with new fluid by one step.
One more thing:when you said". As the pistons continue to move backwards, fluid from the reservoir flows through the Equalization and Fluid Intake & Return Ports into areas "A" &"E, " again to prevent air from entering."
I think that you meant, that the fluid from the A & E flows through the equalization port to the reservior and from the reservoir to the front of the pistons through the Intake & Return Ports, As the piston continue to move backwards.
Didn't you?
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Wednesday, August 6th, 2014 AT 12:31 AM
Tiny
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When the piston moves backwards (back towards its starting position) the piston seals bend forward exposing holes that are drilled into each piston flange (which is covered by the seal when the pistons are at rest or moving forward).
Fluid which is in areas "A" & "E" flow through the now exposed holes in the piston flange and into the area in front of the piston (remember the piston is moving backwards faster than the fluid can return from the brake lines (so the fluid in A & E is used to fill that gap to prevent air from entering.
The fluid in A & E is not pressurized by the backwards movement of the piston because it has an area of escape; through the holes in the piston flange.

Once the piston is back in its starting position, the fluid which is (finally) returning from the brake lines enters the reservoir through the Equalization and Fluid Intake and Return ports.

I hope this clears things a bit.
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Thursday, August 7th, 2014 AT 8:00 PM
Tiny
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Thanks, Freemba.
Maybe the photo is not right.
I took into account that the start position(and last position)of the pistons are as at the picture. And as it is, I understood that the fluid from the lines can return to the reservoir only from the intake and return ports, since the equalization ports are blocked by the piston seals(and as you said fluid can flow through the holes of the piston only through parts A&E to the forward, not opposite). So the piston should returned behind the intake and return ports and also behind the equalization ports in order that the fluid from the lines will flow as you said, shouldn't it?
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Saturday, August 9th, 2014 AT 3:39 AM
Tiny
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The piston does not return behind the equalization port. This port is for the purpose of equalizing pressure on both sides of the piston. Therefore fluid is present there at all times (it made be moving into or out of the area but its there at all times).
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Sunday, August 10th, 2014 AT 1:23 PM

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