Trouble Bleeding Rear Brakes, Rear left one is fine but nothing comes out of rear right Options

[LTom]

I recently overhauled both rear calipers and now i've put them back on they require bleeding. With the help of a friend who did the pedal pushing I first bled the rear left (passenger, uk) caliper which went fine. However the rear right one just will not bleed. Nothing comes out as far as I can tell, not even air. I have taken the bleed nipple off and it is not obstructed, i can blow air through it. What the hell is causing this? I'd really appreciate some help as the weather is grim and my only other means of transportation is a motorbike.

[Galcobar]

Bleeding one port at a time, starting with the port farthest from the master cylinder, is the recommended procedure.

You mention that the pedal stays soft when bleeding. Is it soft when the bleeder ports are all closed, and does it firm up at all with repeated pumping of the pedal with the ports closed?

How are you bleeding the brakes? The Toyota directions, to prevent the system from re-ingesting air, are to use the jar method but with the engine off close the bleeder valve, pump the brake pedal several times to build pressure, and then to release the bleeder valve. Repeat as necessary.

While you were rebuilding the calipers, was the system left open and allowed to drain to the point the master cylinder emptied? If so, you may have to bleed the master cylinder, which requires disconnecting the brake lines.

Often it helps to work backwards. You've already verified the bleeder port is clear. Next step is to verify the caliper is clear, which given its monolithic nature should be simple. I'd also check that the seal on the piston is air tight; if it were twisted, damaged or the lip holding it damaged you could be losing pressure that way.

The final option is a faulty brake booster. This is unlikely, as it would be quite a coincidence for it to fail at the moment you try to reinstall your calipers. However, it's possible and easily tested. If it's not air tight anymore, the system cannot build pressure. First check is with the engine off; depress the brake pedal several times slowly. If the pedal goes down the farthest the first time, but gradually rises after the second or third time, the booster is air tight. The second test begins with the engine running; press and hold the pedal down, then turn turn off the engine. If there is no change in the pedal reserve travel after holding the pedal for thirty seconds, the booster is air tight.

[LTom]

Bleeding one port at a time, starting with the port farthest from the master cylinder, is the recommended procedure.

You mention that the pedal stays soft when bleeding. Is it soft when the bleeder ports are all closed, and does it firm up at all with repeated pumping of the pedal with the ports closed?

How are you bleeding the brakes? The Toyota directions, to prevent the system from re-ingesting air, are to use the jar method but with the engine off close the bleeder valve, pump the brake pedal several times to build pressure, and then to release the bleeder valve. Repeat as necessary.

While you were rebuilding the calipers, was the system left open and allowed to drain to the point the master cylinder emptied? If so, you may have to bleed the master cylinder, which requires disconnecting the brake lines.

Often it helps to work backwards. You've already verified the bleeder port is clear. Next step is to verify the caliper is clear, which given its monolithic nature should be simple. I'd also check that the seal on the piston is air tight; if it were twisted, damaged or the lip holding it damaged you could be losing pressure that way.

The final option is a faulty brake booster. This is unlikely, as it would be quite a coincidence for it to fail at the moment you try to reinstall your calipers. However, it's possible and easily tested. If it's not air tight anymore, the system cannot build pressure. First check is with the engine off; depress the brake pedal several times slowly. If the pedal goes down the farthest the first time, but gradually rises after the second or third time, the booster is air tight. The second test begins with the engine running; press and hold the pedal down, then turn turn off the engine. If there is no change in the pedal reserve travel after holding the pedal for thirty seconds, the booster is air tight.

Thanks for taking the time to write this.

Yes, the pedal stays soft when all the bleeders are closed.

The lines were disconnected for a week while I waited for parts and it is possible that air got sucked into the master. How would I go about bleeding the master?