Does pumping with brake pedal while the resevoir is empty still take out the fluid?


Asked by cbbv Apr 17, 2013 at 03:19 AM about the 1990 Opel Corsa

Question type: Maintenance & Repair

while i used the method of two person to empty the system.(one push and release the brake pedal and the other open and close the nipple nut).
IF the resevoir is empty and there is left brake fluid only in the master cylinder chambers and in the pipes that located between the master cylinder and the wheels and my assistant keep on pumping the brake pedal,will all the brake fluid get out or from this point(the moment that the resevoir is empty)the brake pedal action will not get out  the rest of the brake fluid unless we refill the resevoir?
thank in advance.

3 Answers

No. Once the master cylinder reservoir is empty and when the petal is pumped, the plunger is only pushing air and the air will compress but only ever so slightly, not enough to force the remaining brake fluid out, through the brakes lines. The fluid does not compress, that's the whole idea, the plunger pushes the fluid to the calipers or 'slave cylinder' on shoe/drum brakes. Are you changing fluid? If so keep adding new fluid until out comes out clean and clear and no air with it. You notice that there are two reservoirs. One for 2 wheels and one for the other two wheels. If a brake line breaks or leaks you will still have brakes on at least a pair or wheels and not lose all's not like in the movies and the 'bad guy' cuts one brake like..she goes down the mountain......iiiiiieeeeeee! brakes....a shot of the brake line with fluid coming out, panic and stomping on the petal, careening around cars horns honking..that would only happen if the brake lines were cut in front and back

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Now. Some cars use a diagonal, one back wheel and one front wheel on one 'circuit', and some cars one brake circuit is front the other rear. Cars with anti-lock brakes may require a slightly different procedure on the rear brakes. Because the system is pressurized, have your assistant turn the car on, press on the brake pedal, turn off the ignition and then just rest his/her foot on the pedal. Open the bleeder valve and let the fluid stream out for about five seconds or so. Close the valve and add some more fluid at the master cylinder. Repeat.

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Trying to find images not copyrighted, and that is getting more difficult but I think these are OK, I just wanted to show you, if it appears to have only one reservoir it still works the same way with two braking circuits. 70% of stopping is done by the front brakes. This image shows front and rear, but there are cars with diagonal. but NEVER one 'circuit' for left and one for right side.

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