MK4 VW; Master Cylinder / Brake Issues

[mr_cb7]

Master cylinder issues. I just replaced both rear calipers on my mother’s mk4 beetle. While removing the second caliper I had to go help a family member and I clipped closed the disconnected rubber brake line going to the caliper to prevent fluid loss. When i came back the tire I had lying next to the car must have tipped over and the clip holding the.line closed fell off and most of the fluid in the reservoir leaked out. I filled it back up and continued on, but after bleeding the wheels the pedal is still soft, and one of the rear calipers is sticking. Do I have to prime the master? And if so can this be done without removing from the car?

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[college man]

If your getting fluid out when your bleeding the master sounds like its pumping.
It could be the stuck caliper not pushing on the pads to the rotor. I would resolve the caliper
issue first.

[Mechmann]

I agree to get the caliper fixed first to eliminate that problem. Also, if you are bleeding manually with the master cylinder, make sure you are using the correct technique. Have a buddy push the pedal for you: 1) Open bleeder valve; 2) Push pedal down and hold; 3) Close bleeder valve; 4) Release pedal. Repeat until all the air bubbles are gone from the line. (A clear hose on the bleed nipple works best to see the air bubbles come out.) That way the master cylinder acts like a pump to positively push the fluid out. Good luck.

[jonathan]

If all the fluid was gone from the master cylinder, you have to bleed it again, its easy, first bench bleed it, ericthecarguy has a video about this, fill it up with fluid, then if you are working alone install the master cylinder loosely first and tighten the brake lines to it but leave them loose, put a giant screwdriver or somethibg on the brake pedal and jam it against the seat, then tighten the brake lines and release the screwdriver from the pedal, repeat this process 4 or 5 times untill all the air is removed

[Author]

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