I bled the rear brakes on my Toyota Yaris 2007 with 170k miles. The problem is air being sucked in through the threads of the bleeder screw (only when bleeding: air is not introduced if the bleeder screws are fully closed). Is it a good idea to wrap the threads of the bleeder screw with some teflon (white plumbing) tape while doing the bleeding? And then undo the screw, remove the tape, and put the screw back?
No. I use a MightyVac for brake bleeding and it always has small air bubbles from the threaded fitting. What you want to get rid of is the gaps in the fluid in the bleed line. Don't worry about the small bubbles.
Right. I am trying to get rid of the gaps in the fluid in the bleed line, as you wrote. There are always gaps! I assumed it is because of the air seeping in through the bleeder screw. I didn't discover any fluid leaks or any air introduced into the brake lines during regular driving, no sinking brake pedal. But the brake pedal is way too soft.
It sounds like you're bleeding it wrong. If you close the bleeder screw before you release the brake pedal then no air should be sucked into the system.
And then undo the screw, remove the tape, and put the screw back?
When you undo the screw, air will be introduced and all your work will be for naught.
I use a vacuum pump similar to Doc's MightyVac. It's a one-man job.
Don't use the tape, and don't remove the bleeder screw. You want to unscrew them just enough to get a solid stream of new brake fluid then close it off while maintaining suction.
Ok well please give complete information when asking questions. Thanks.